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Corresponding to the different phase‐shifts of the interference modes, the whispering gallery mode resonator‐based Fano resonance exhibits a variety of unique spectral lineshapes that can be applied to sensing, optical signal processing, and so on. However, most approaches to lineshape tuning aim to alter the propagation phase‐shift or coupling strength, and generally suffer from relatively low efficiency and limited tuning range. In this paper, with a carefully designed waveguide‐taper coupled micro‐ring resonator structure and the assistance with the grating‐coupler, for the first time a near full‐lineshape selectivity of the Fano resonance is demonstrated in two isolated tuning dimensions of the frequency and transverse space, which means arbitrary lineshapes including the Lorentzian‐dip, asymmetric Fano peak or electromagnetically‐induced‐transparency (EIT)‐like peak can be obtained at a specific resonance wavelength in the whole C‐band. In addition to the different types of line shapes, the extinction ratio can also be enhanced by dynamically tuning the coupling position. This research provides an efficient approach to manipulate the transmission spectra of the Fano resonance, which is of great importance in promoting its further applications on integrated photonics platforms. [ABSTRACT FROM AUTHOR]

Light polarization control is a target in photonics, and this paper provides a comprehensive review of research from various groups on the silicon‐on‐insulator (SOI) platform. It draws comparisons between devices such as polarization splitters (PS), polarizers, and polarization splitters/rotators (PSR). These devices are fabricated using various technologies, including silicon nanowires, ridge waveguides, hybrid plasmonic waveguides, and subwavelength grating (SWG) waveguides. A detailed review of polarizers used as cleanup filters in splitters is initiated. Subsequently, various polarization splitters utilizing asymmetric directional couplers (ADCs), which typically exhibiting low extinction ratios (ERs), are delved. To enhance ERs, a detailed comparison of methods outlined in the literature is provided. One notable method includes integrating on‐chip polarizers at both ports to eliminate unwanted light fractions and achieve exceptionally high ERs. Furthermore, SWG‐based polarizers and splitters commonly face issues with Bragg reflections that can affect other photonic devices and lasers and ways to minimize unwanted polarization back reflections in SWG‐designed polarization control devices are examined. Finally, emerging applications in mid‐infrared (MIR) sensing are explored, highlighting the necessity of polarization rotators for on‐chip transverse electric (TE) operation, since quantum cascade lasers, the primary sources in this range, emitting radiation in the (TM) mode. [ABSTRACT FROM AUTHOR]

Robust edge states and corner states in photonic topological insulators provide effective ways to manipulate the propagation of electromagnetic waves. Bandgaps of the previously reported photonic topological insulators are independent of each other. In this paper, a higher‐order valley photonic insulator composed of arrays of dendritic structure is designed. The band structure shows an overlapped bandgap is observed, and the overlapped bandgap divides the band structure into three bandgaps. The evolution of the overlapped bandgap is investigated by changing the geometric parameters and increasing the fractal to break the C3v symmetry drastically. Besides, it is notable that the band structure of the proposed valley photonic insulator is flat bands. It is demonstrated that undistorted transmission can be observed as a plane electromagnetic wave transmits through the proposed valley photonic insulator. The interface consisting of two valley photonic structures with distinct topological nontrivial phases is constructed. Edge states and corner states with strong energy localization are obtained in multi‐band frequencies. Remarkably, two triangular structures with different Wannier center configurations both have corner states in the same bandgap, which does not obey the valley selectivity. The phenomenon is caused by the weak valley locking property due to the overlapped bandgap. The proposed valley photonic insulators are expected to benefit applications in optical devices such as topological lasers. [ABSTRACT FROM AUTHOR]

Liquid‐crystal random lasers (LCRLs) represent a burgeoning field in soft‐matter photonics, holding promise for ushering in an era of ultrathin, versatile laser sources. Such lasers encompass a multitude of remarkable features, including wide‐band tunability, large coherence area and, in some cases, multidirectional emission. In this paper, an LCRL is developed by doping a laser dye, pyrromethene 597 (PM597), into cholesteric LC, but achieving a wide‐range wavelength‐controllable (560–720 nm) bandgap lasing through voltage control. Bandgap lasing intriguingly occurs in media with extremely low dye gain, which is mainly contributed by the extremely high photon density of states (DOS) at the edge of the LC bandgap. In addition, the utilization rate of the fluorescence spectrum (550–750 nm) of laser dye PM597 is as high as 80%. The multivariate linear regression model is used to characterize the inherent relationship between the lasing intensity emitted by LC and the photon DOS, fluorescence quantum yield, and internal scattering under specific pumping energy. This model shows the potential to predict the critical conditions of laser emission accurately and provides the capability to design and fabricate large‐scale multifunctional responsive photonic crystals using a simple fabrication procedure. [ABSTRACT FROM AUTHOR]

Reconstructive spectrometers, which leverage the compressive sensing technique and computational algorithm, are promising solutions for high‐performance integrated spectrometers. Among the various options for realizing reconstructive spectrometers, stratified waveguide filters (SWFs) have emerged as a particularly attractive choice due to their ultra‐compact size and high performance. However, previous demonstrations of SWFs on silicon substrates have suffered from suboptimal and non‐reproducible spectrometer performance due to the brute‐force random design approach. In this paper, applying a bio‐inspired inverse design algorithm to the system level of multiple correlated SWFs is proposed. The algorithm allows for the precise and optimized design of the SWFs in order for higher spectral resolution of each SWF and lower spectral cross‐correlations between any two SWFs, overcoming the limitations of previous methods. The effectiveness of this approach is demonstrated by implementing a reconstructive spectrometer on a silicon nitride (SiN) platform, which is more thermally stable and can support a wider optical range than silicon. [ABSTRACT FROM AUTHOR]

The orbital angular momentum (OAM) of light, which is associated with the rotation of the phase structure, gives rise to numerous novel physical phenomena inlight–matter interactions. However, the direct generation of scalar OAM lasers with power‐handling capability and controllable states at the source remains challenging owing to mode degeneracy, handedness selection, and nonlinear thermal effects, which can even lead to topological charge splitting. This paper proposes a novel approach that allows spatial mode‐conversion‐controlled laser oscillation in a high‐gain OAM laser cavity with an integrated spiral‐face output coupler (SFOC). By adapting position‐dependent resonant modes, scalar optical vortices with a record power level (>60 W), high purity (>90%), and controllable OAM states (ħ or −8ħ) are demonstrated. Further, the dynamic process of OAM generation and evolution in the cavity is revealed. The concept presented herein opens a new route for the generation of OAM laser sources toward high power levels and holds promise for advancing classical and quantum optics, particularly in the area of light–matter interactions. [ABSTRACT FROM AUTHOR]

Optoelectronic implants have gained increasing attention over the last ten years for their clinical applications, such as optogenetics, photodynamic therapy, and deep‐tissue physiological sensing, which are expected to diagnose and treat a large number of diseases, such as Parkinson's and Alzheimer's diseases, visual impairment, and cancer. One of the main challenges for biomedical optoelectronics is to produce a compact, biocompatible system that delivers optical energy into specific tissue regions. While early‐stage devices are initially adopting batteries or wired solutions for energy supply, recent development has shifted toward wireless devices based on alternative methods, such as wireless power transmission, kinetic energy, and photovoltaic harvesting, which do not normally require periodic replacement or servicing and do not constrain the movement of the patient. In this paper, the principles of the main biomedical applications of implantable optoelectronic devices are reviewed. Recent developments in wireless implantable optoelectronic devices are summarized and sorted by their energy transfer mechanisms. These energy transfer techniques are compared in terms of quantitative parameters (electrical power, optical power, operating frequency, size, weight, and operating range), application fields where they are tested, and main advantages and limitations. [ABSTRACT FROM AUTHOR]

Diffractive Optical Elements (DOEs) are indispensable tools across numerous technological domains due to their capacity to manipulate light with sophistication and versatility. Their compact dimensions, lightweight nature, and compatibility with diverse materials render DOEs as prime candidates for integration into various optical systems, spanning from consumer electronics to state‐of‐the‐art scientific devices. Thus, DOEs stand as essential catalysts in technological advancement, facilitating innovation and unlocking new applications across a broad spectrum of disciplines. In this comprehensive review paper, Numerous types of DOEs widely acknowledge for their efficacy in both free space optics and imaging applications are delved. Beyond mere enumeration, their practical applications, elucidating their transformative impact on these fields are carefully examined. Furthermore, the challenges encountered in their implementation are dissected, paving the way for insightful discussions on future trajectories and advancements. [ABSTRACT FROM AUTHOR]

The formation of dense plasmas inside dielectric materials by ultrashort laser pulses has many applications ranging from refractive‐index modifications to the formation of channels and voids. Furthermore, such plasmas enable the fundamental investigation of ultrafast non‐equilibrium dynamics in highly excited materials. The present paper provides an overview of current experimental approaches to investigating such plasmas. Much information about the plasma relaxation is obtained by measuring the spatial and temporal evolution of the dielectric properties of the excited material through time‐resolved absorption and phase‐shift measurements. In order to investigate and resolve the individual stages of plasma formation, experimental approaches with a temporal resolution beyond the capabilities of traditional optical pump‐probe studies are required. Recent examples for schemes that may enable the investigation of the plasma formation with sub‐cycle time resolution are thus reviewed. These include recent results from time‐resolved high‐harmonic generation as well as the two‐color pump‐probe analysis of non‐perturbative low‐order wave mixing for the tracking of strong‐field excitation dynamics. Alternative approaches employ attosecond transient absorption spectroscopy, attosecond polarization spectroscopy and nonlinear photoconductive sampling for resolving the temporal evolution of the carrier dynamics down to sub‐optical‐cycle timescales. [ABSTRACT FROM AUTHOR]

Extracting the desired information from sensor data with various internal and external effects is a significant challenge in sensor applications. Difficult‐to‐control factors such as temperature, humidity, and sample position can significantly affect the stability and reliability of sensor data. In this paper, a deep learning‐based glucose sensing method that is robust to variations in sample position is proposed. It is shown that the variations in sample position affect the sensor data measured by the designed split ring resonator‐based microwave sensor. Then, artificial neural network and 1D convolutional neural network (CNN) models are evaluated for extracting glucose concentration information from the sensor data measured at random sample positions. The concentration of the glucose solution ranged from 1% to 23% (2% increments). The 1D CNN with all frequencies (0.5–18 GHz) of the and datasets outperformed the other model, with a mean absolute error (MAE) of 0.695% and a mean squared error (MSE) of 0.876 evaluated via cross‐validation. The study demonstrated that the sensor system can be applied in real life by performing fruit Brix estimation based on transfer learning of the previous 1D CNN network, and the MAE and MSE are 0.450% and 0.305, respectively. [ABSTRACT FROM AUTHOR]

Mechanoluminescence (ML) is a fascinating phenomenon with diverse applications in pressure sensing, damage detection, and stress distribution visualization. However, most ML materials exhibit instantaneous photon emission that requires real‐time recording with a photodetector, and thereby circumscribing their applicability predominantly to real‐time stress‐sensing scenarios. In this work, a novel method is introduced for non‐real‐time stress sensing utilizing Li0.1Na0.9NbO3:Pr3+ phosphor, which allows for the retrieval of pressure location and intensity even 20 days after the event. The influence of heat and pressure on the trap depth distribution is analyzed using thermoluminescence (TL) and ML measurements, and it is proved that both heat and pressure release the captured electrons in the same traps. Leveraging the intricate competition between mechanical and thermal detrapping processes, stress information can be accessed through TL imaging. Furthermore, an algorithm is proposed based on this phenomenon to authenticate the stress information. This research not only advances the fundamental understanding of ML phenomena but also introduces a novel approach for applications such as mechano‐history indicators, security papers, and advanced data storage systems. [ABSTRACT FROM AUTHOR]

Functionalized optical fiber tips featuring miniature sizes and diverse functions have broken the limitations of traditional optical fiber with fixed shapes and single materials, significantly enriching the application scenarios in communication, sensing, imaging, and other fields. However, the unconventional shape presents challenges in manufacturing arbitrarily sophisticated 3D micro/nano structures on optical fiber tips. Femtosecond laser 3D nano‐printing (FL‐3DNp) technology injects new vitality into the functionalization of fiber tips due to its high‐precision, customizable structure, and real 3D processing abilities, as well as advantages of non‐vacuum, maskless, and plentiful materials. This paper extensively compares the key performance parameters of various micro‐nano manufacturing technologies for functionalizing optical fiber probes and focuses on the FL‐3DNp technology. In addition, the latest research progresses are systematically presented from the perspective of structure and application. Finally, the current research challenges and future development directions in this emerging field are discussed, aiming at providing scientific and industrial guidance for FL‐3DNp in functionalizing optical fibers. [ABSTRACT FROM AUTHOR]

Chiroptical response, demonstrating chiral interaction between optical vortex and chiral structure, plays an important role in variety of fields like optics and material science. However, the flexibility and efficiency of chiral structure fabrication are limited due to mask requirement and a point‐by‐point constructing strategy. In this paper, a novel chiral lithography method is proposed that utilizes optical vortex phase beam shaping to achieve chiral structure processing with high efficiency and flexibility. By programming topological charges of the vortex phase, chiral structures with adjustable appearance, rotation, and chirality can be produced using femtosecond laser single pulse exposure. Transmittance measurements of fabricated chiral structures array confirm a 66% helical dichroism that is predicted by simulation. Moreover, with the aid of convolutional neural networks (CNN), an accuracy of 98% in Orbital Angular Momentum (OAM) recognition can be achieved. This chiral lithography method provides an alternative for chiral structure fabrication and holds promise in the development of chiral optics, optical communications, and next‐generation optical devices. [ABSTRACT FROM AUTHOR]

In recent years, the emergence of metasurfaces has brought revolutionary changes to the generation and processing of vortex beams, triggering widespread research interest. Meanwhile, the longitudinally varying features of propagating beams provide new design freedom for realizing multi‐dimensional optical manipulation and promote the advancements of related areas such as microscopic detection, microfabrication, and biomedical applications. In addition, self‐accelerating Bessel beams are promising for a wide range of applications such as particle manipulation and medicine due to their nondiffracting, self‐healing as well as obstacle avoidance properties. In this paper, a novel kind of curved transmitted high‐order Bessel beams with longitudinally varying features based on form‐birefringent metasurface, by simultaneously manipulating the phase profiles of output orthogonal polarization components is demonstrated. Multiple dimensions of the beam, including the propagation trajectory, polarization state, and orbital angular momentum, can be tailored arbitrarily. For verifying the feasibility of the demonstrated method, two samples with different propagation trajectories, as well as different variations of orbital angular momentum, are designed and experimentally demonstrated. Such a novel approach can open new doors for the manipulation of vortex beams and can be used for depth sensing and distance measurement in complex environments. [ABSTRACT FROM AUTHOR]

Non‐separable states of structured light have the analogous mathematical forms with quantum entanglement, which offer an effective way to simulate quantum process. However, the classical multi‐partite non‐separable states analogue to multi‐particle entanglements can only be controlled by bulky free‐space modulation of light through coupling multiple degrees of freedom (DoFs) with orbital angular momentum (OAM) to achieve high dimensionality and other DoFs to emulate multi‐parties. In this paper, a scheme is proposed to directly emit multi‐partite non‐separable states from a simple laser cavity to mimic multi‐particle quantum entanglement. Through manipulating three DoFs as OAM, polarization, and wavevector inside a laser cavity, the eight‐dimensional (8D) tripartite states and all Greenberger‐Horne‐Zeilinger (GHZ)‐like states can be generated and controlled on demand. In addition, an effective method is proposed to perform state tomography employing convolutional neural network (CNN), for measuring the generated GHZ‐like states with highest fidelity up to 95.11%. This work reveals a feasibility of intra‐cavity manipulation of high‐dimensional multipartite non‐separable states, opening a compact device for quantum‐classical analogy and paving the path for advanced quantum scenarios. [ABSTRACT FROM AUTHOR]

Metalens, a metasurface with a focusing phase, has been the focus of research due to its immense potential for use in imaging and display technology. Traditional lens and optical imaging systems rely on phase accumulation, however metalens with subwavelength structures provide a disruptive path for miniaturized optical imaging systems by allowing unfettered modulation of incident light's phase and amplitude. Recently, extensive efforts have been devoted to exploring new design strategies, new functionalities, and possible applications. This paper reviews the development, principle, classification, and research status of metalens. In particular, this review focuses on the progress and challenges of improving imaging quality and expanding imaging diversity, including improvements of resolution, enhancement of depth of field, extension of field of view, and achromatism. Lastly, the prospects of metalens in the future display are summarized, and the application potentials of metalens in novel 3D display, intelligent and bionic display, as well as nano‐pixelate light‐emitting display (NLED) are emphasized. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots (QDs) have been widely studied in display panels due to their near‐unity fluorescence quantum yield and the ability to tune colors across a wide gamut. However, the challenge persists in creating full‐color QD arrays with the necessary precision for high‐resolution display applications in the next generation. This paper introduces a femtosecond laser‐induced forward transfer (FsLIFT) technology that integrates deposition pattern and alignment in a single transfer step. This development enables the fabrication of high‐resolution full‐color QD films. The ability of FsLIFT to precisely locate red, green, and blue QDs in a designated position allows to obtain arbitrarily shaped full‐color patterns and pixel arrays with a resolution of 1.78 µm. In addition, the potential for optoelectronic devices is ensured by the preserved photophysical properties, high smoothness, and continuity of the transferred QD films. Consequently, the light‐emitting diodes (LEDs) are successfully fabricated based on the transferred QD films. This study expects that the introduced straightforward patterning technology, offering high freedom, precision, and repeatability, will contribute to advancing the development of full‐color high‐resolution displays based on QDs. [ABSTRACT FROM AUTHOR]

The Jones matrix is a powerful quantitative tool for polarimetric imaging and characterization, where the matrix elements represent the intrinsic optical properties of the anisotropic objects on interaction with the polarized light. Most of the state‐of‐the‐art single‐shot Jones‐matrix imaging techniques rely on interferometric methods, which makes the design complex with the use of large number of polarization optics and produces space‐bandwidth limitations. The simultaneous extraction of Jones matrix elements with a compact system design is still a technical challenge in view of its potential applications in biomedical and real‐time characterization scenarios. In this paper, the imaging features of the in‐line holography are exploited to develop a compact polarization in‐line holography (PIH) system capable of single‐shot extraction of Jones‐matrix elements. The technique achieves simultaneous orthogonal polarization state generation and corresponding polarization multiplexed in‐line hologram detection by utilizing a compact polarization geometry. The imaging compatibility and measurement accuracy of the method is experimentally validated by the real‐time synthesis of Jones‐matrix elements corresponding to custom designed polarization sensitive samples and standard birefringent resolution target. Furthermore, to demonstrate the application of the system in dynamic imaging, the transient polarization changes of a custom‐designed parallel nematic liquid crystal display (LCD) are investigated. [ABSTRACT FROM AUTHOR]

In this paper, a spectrally efficient silicon photonics phase‐diverse direct‐detection receiver based on asymmetric self‐coherent detection is proposed. The receiver is hardware efficient and composed of only two photodiodes and two analog‐to‐digital channels to accurately recover complex double‐sideband signals by leveraging an optimized integrated silicon racetrack resonator with near‐ideal phase responses. Moreover, the periodicity of the resonator response enables the receiver to support multi‐channel transmission such as dense wavelength‐division multiplexing. The receiver circuit is fabricated and characterized. In 40‐km transmission experiments, a record net electrical spectral efficiency of 7.10 bit s−1 Hz−1 per wavelength and per polarization is achieved, where a net 208‐Gb s−1 32QAM transmission is demonstrated using 29.3‐GHz electrical bandwidth. Furthermore, the receiver achieves net 220‐Gb s−1 16QAM transmissions in 14 channels from 1527 to 1550 nm with 205‐GHz spacing, and a maximum 240‐Gb s−1 net capacity at a single channel. Such a performance is reached with only standard coherent digital signal processing stacks including all‐linear equalization. [ABSTRACT FROM AUTHOR]

Mid‐infrared (mid‐IR) ultrafast lasers are widely employed in biomedicine, molecular spectroscopy, material processing, and nonlinear optics. With the improvement of fiber gain media and other fiber optical elements, low‐cost, compact, and high‐efficiency fiber lasers open up new opportunities for 2–4 µm pulse generations, which calls for a comprehensive review of their mode‐locking mechanisms, gain media, and fiber laser system performance. This paper, beginning with an overview of pulse‐generation technologies, reviews recent progress on 2–4 µm mid‐IR ultrafast fiber lasers, including Tm3+‐, Ho3+‐doped, Tm3+/Ho3+ codoped silicate fiber 2 µm lasers, and Er3+‐, Dy3+‐doped, and Ho3+/Pr3+ codoped ZBLAN fiber 2.5–4 µm lasers. Among them, the status of 2–4 µm ultrafast fiber lasers based on 2D material passive mode‐locking is emphatically discussed. Meanwhile, the novel advances on mode‐locking and gain fibers of mid‐IR ultrafast fiber lasers are explored. Furthermore, current and prospective applications of such laser systems are also introduced in detail. This review finally summarizes challenges associated with future development of mid‐IR ultrafast fiber lasers, which provides an outlook on how to achieve more desirable laser performance (e.g., higher average power, higher pulse energy, and longer emission wavelength) that can lead to more practical uses of such lasers. [ABSTRACT FROM AUTHOR]

The Control of spatial electromagnetic (EM) waves has always been an attractive prospect, especially with the emergence of metasurfaces, which introduce additional manipulating methods and degrees of freedom. In this paper, a design is proposed to realize reconfigurable and programmable space channels for non‐reciprocal transmissions of EM waves through the use of active metasurface. The layout of the chessboard pattern is preferred for constructing the metasurface, which is composed of two kinds of meta‐atoms. One type of meta‐atom is independently controlled for the transmission gain, attenuation, and phase shift, while the other type is independently controlled for the transmission attenuation and phase shift only. The use of power amplifiers (PAs) to achieve transmission gain in the meta‐atoms can actualize the performance of non‐reciprocal transmissions. The programmable operations of phase shift and attenuation in meta‐atoms can dynamically establish varied spatial channels. A prototype of the active metasurface is fabricated and measured. In the measurements, multiple types of reconfigurable and programmable non‐reciprocal transmission channels are observed clearly, verifying the validity of the proposed method. [ABSTRACT FROM AUTHOR]

Metasurface‐based optical field manipulation has significantly broadened the application range of micro‐optical components and integrated optics, gradually replacing bulky and complicated optical components. With the continuous development of micro and nano processing technology as well as computational analysis technology, metasurfaces have progressively shown their superior application prospects. After demonstrating tremendous results in classical optical applications, their application range has now extended to the field of quantum sensing. Due to their unique properties, such as small planar size, easy integration, flexible performance design, and tunable functionality, they have opened up a series of novel and rich applications for generating, manipulating, controlling, and detecting optical fields. In this paper, the basic principle and implementation of quantum measurement are presented and an overview of the design principles of metasurfaces, along with a summary of the latest advancements and potential applications of these surfaces in optical field modulation techniques for quantum precision measurement. Additionally, a thorough discussion and analysis of the challenges encountered by metasurfaces and their future development prospects is provided. Metasurfaces offer brand‐new opportunities for low‐cost, high‐performance, multifunctional miniaturized quantum sensors and are expected to play a significant role in the development of next‐generation quantum sensors. [ABSTRACT FROM AUTHOR]

Laser interferometry is one of the most accurate measurement technologies whose displacement resolution can reach the femtometer (fm) level. With the development of Micro‐Electro‐Mechanical Systems(MEMS) technology, many excellent optical interferometric MEMS sensors have emerged, which play an essential role in intelligent manufacturing, aerospace, and many other fields. Among them, optical interferometric MEMS accelerometers develop rapidly due to their high sensitivity, low noise, and anti‐electromagnetic interference advantages. Lots of research in optical interferometric chip design, micro‐nano fabrication process, signal demodulation algorithm, and range extension technology are performed, and different types of MEMS accelerometers based on the optical interferometric principles are developed, which have been demonstrated and applied in the fields of disaster monitoring, equipment operation and maintenance, and resource exploration. This paper reviews the development status of optical interferometric MEMS accelerometers, mainly focusing on the critical problems and solutions that need to be solved in the development process of optical interferometric accelerometers, and finally introduces the typical application scenarios. [ABSTRACT FROM AUTHOR]

Nonlinear pulse compression techniques have been applied widely in the pursuit of ultra‐intense laser pulse with extremely high pulse energy (≈mJ) and extremely short pulse duration (≈sub‐10 fs). Although postcompression techniques using dispersive gratings or chirped mirrors have achieved 1 TW few‐cycle pulses, further increasing of the pulse intensity is limited by the damage threshold of dispersive optics, especially when self‐focusing and ionization in the propagation medium are considered. To overcome such limitations, ultrashort pulses self‐compression techniques without vulnerable dispersive optics have been explored in the past two decades. In this paper, the latest advances in these techniques will be reviewed with a discussion on the progress of various experimental approaches as well as their potential applications and roles in generating extremely intense optical fields for strong‐field physics research. [ABSTRACT FROM AUTHOR]

In recent years, compact micro‐/nanofiber sensors with fast response and high resolution have become a hot field in sensing and nanotechnology. In addition to the unique properties of microfibers such as strong evanescent field, low optical loss, and easy integration, microfiber knot resonators further improve the sensing capability due to their resonance properties. The potential high‐quality factor allows higher sensing sensitivity and resolution, which is very attractive for optical sensing at the micro‐/nano scale. More application potential can be effectively stimulated by improving the structure shape or principle or combining with functional sensitive materials. This paper first introduces the preparation process and spectral characteristics of conventional microfiber knots and then focuses on three new types of devices for enhancing the sensing performance, namely material‐coated, shape‐improved, and principle‐extended, and briefly analyzes their spectral properties. In addition, the research progress and applications of these sensors are summarized. Finally, the existing problems in this field are analyzed, and the directions for further development are discussed and prospected. [ABSTRACT FROM AUTHOR]

The emergence of higher‐order topological insulators (HOTIs) has greatly expanded the family of topological materials. While the co‐dimensional bulk‐boundary correspondence is observed in platforms, such as acoustics and photonics, realizing three‐dimensional (3D) photonic HOTIs is relatively challenging due to the complex properties of electromagnetic waves such as polarizations, scattering, and refractive index. In this paper, a photonic HOTI with a simple multilayer structure that supports higher‐order hinge states is proposed. By inserting a central metallic pillar in the unit cell, the 3D bandgap can be well extended, enabling pure and distinguishable surface and hinge modes. The lattice is reconfigurable and flexible, allowing for hinge and surface waves to be generated by controlling the geometrical length of sub‐lattices. The idea of distinguished higher‐order hinge modes is also extended to enlarged higher‐orbital bandgaps. Furthermore, by introducing a central disclination in this photonic model, the one‐dimensional (1D) vertical disclination mode is obtained which is not seen in existing photonic HOTIs. The findings open the door for a high‐performance topological optical apparatus that features efficient one‐way light propagation and energy concentration. [ABSTRACT FROM AUTHOR]

Label‐free super‐resolution (LFSR) imaging relies on light‐scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super‐resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state‐of‐the‐art in this field, and to discuss the resolution boundaries and hurdles that need to be overcome to break the classical diffraction limit of the label‐free imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction‐limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super‐resolution capability that are based on understanding resolution as an information science problem, on using novel structured illumination, near‐field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere‐assisted approaches. To this end, this Roadmap brings under the same umbrella researchers from the physics and biomedical optics communities in which such studies have often been developing separately. The ultimate intent of this paper is to create a vision for the current and future developments of LFSR imaging based on its physical mechanisms and to create a great opening for the series of articles in this field. [ABSTRACT FROM AUTHOR]

Electrical signals derived from optical sources have achieved record‐low levels of phase noise, and have demonstrated the highest frequency stability yet achieved in the microwave domain. Attaining such ultrastable phase and frequency performance requires high‐fidelity optical‐to‐electrical conversion, typically performed via a high‐speed photodiode. This paper reviews characteristics of the direct photodetection of optical pulses for the intent of generating high power, low phase noise microwave signals from optical sources. The two most popular types of photodiode detectors used for low noise microwave generation are discussed in terms of electrical pulse characteristics, achievable microwave power, and photodetector nonlinearities. Noise sources inherent to photodetection, such as shot noise, flicker noise, and photocarrier scattering are reviewed, and their impact on microwave phase fidelity is discussed. General guidelines for attaining the lowest noise possible from photodetection that balances power saturation, optical amplification, and amplitude‐to‐phase conversion are also presented. [ABSTRACT FROM AUTHOR]

A novel photonic terahertz measurement system based on a frequency‐modulated continuous‐wave (FMCW) radar approach is presented. In previous works, fast frequency modulation has been demonstrated in connection with a continuous wave terahertz spectroscopy setup based on the photomixing principle. In this paper, a terahertz radar based on both a photomixing transmitter and a photomixing receiver, in contrast to the rigid spectroscopy approach, is reported. Hereby, frequency modulation bandwidths of more than 1.65 THz in radar operation is achieved. This corresponds to an order of magnitude more than what is previously achieved by terahertz radar systems. At the same time, measurement rates can be achieved that are comparable with radar systems based on Monolithic Microwave Integrated Circuits (MMICs) according to the current state of the art. Within the scope of the work, two operating modes are realized, one with a measurement rate of about 560 Hz at 600 GHz modulation bandwidth and one with 200 Hz at 1.65 THz modulation bandwidth, which can be set within the spectrum from 50 GHz to about 4.5 THz. The possibility to adjust the operating range of the radar without necessary hardware adaptations is another unique feature of the presented system, which allows the operator to choose a suitable frequency band that corresponds best to a certain measurement scheme via software settings. Besides the potential for multi‐layer thickness inspections, the capabilities of this technique for terahertz imaging applications are presented. [ABSTRACT FROM AUTHOR]

The titanium dioxide nanosphere (TiO2 NS) is a moderate refractive index (MRI) nanostructure which can support Mie resonances such as magnetic dipole resonance (MDR), electric dipole resonance (EDR), etc. However, TiO2 is a wide indirect band gap (3.2 eV) semiconductor, and TiO2 NSs cannot be excited to emit luminescence by near‐infrared (NIR, 770 nm–800 nm) femtosecond (fs) lasers. In this paper, a MDR‐induced nanoscale plasmon source is conceived to provide a large number of hot electrons, which can be used to light up TiO2 NSs. The effect of different metals (Titanium‐Ti, Palladium‐Pd, Gold‐Au) as the MDR‐induced nanoscale plasmon sources on the optical response of TiO2‐based hybrid NSs is studied. This work provides a new strategy for the application of TiO2‐based hybrid NSs as integrated efficient nanoscale white light sources. [ABSTRACT FROM AUTHOR]

Polarization manipulation is essential in photonic integrated circuits and has numerous applications in various fields, such as optical communication, nonlinear optics, and quantum optics. Advances in nanofabrication have enabled the integration of subwavelength‐structured metamaterials on optical waveguides, providing unprecedented optical manipulation capabilities beyond classical waveguide‐based architectures. In this paper, the polarization space is demonstrated to be fully manipulated by a dielectric metamaterial composed of nanoholes and nanoslots. This approach offers competitive performances for key polarization components, including the polarizer, polarization beam splitter, and polarization‐splitter‐rotator, while maintaining ultra‐compact coupling regions of 18×1 µm2, 16×1.1 µm2, and 13×1 µm2 respectively. The devices are designed by manipulating the phase and amplitude of all possible eigenmodes supported in the waveguide, which is inherently scalable and versatile for on‐chip mode and wavefront manipulation. The unique properties of metamaterials provide powerful tools for on‐chip polarization manipulation and offer new possibilities for the development of compact and high‐performance photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Large‐scale silicon optical switches are essential to support the ever‐increasing data traffic. Among the various switching architectures, the well‐known switch‐and‐select (S&S) architecture has the advantages of low crosstalk and strict non‐blocking. However, it suffers from high path‐dependent losses as the waveguide crossings increase dramatically with the number of ports. In this paper, a large‐scale 32 × 32 S&S optical switch on a multi‐layer Si3N4‐on‐SOI platform is reported. The optical switch chip incorporates 1984 broadband thermo‐optic Mach‐Zehnder interferometer (MZI)‐based switch elements, 246 016 three‐dimensional (3D) waveguide crossings, and 2048 interlayer couplers. Both ≈1‐mdB‐loss 3D waveguide crossings and ≈0.3‐dB‐loss interlayer couplers are realized, significantly reducing the overall insertion loss and footprint of the switch chip. The measured average fiber‐to‐fiber insertion loss is 12.88 dB at the 1580 nm wavelength. In addition, the crosstalk is less than −20.7 dB over the 110‐nm wavelength range. The power consumption of the entire switch chip is only ≈0.98 W due to the air trenches and substrate undercut. High‐fidelity optical transmission of a 50 Gb s−1 quadrature phase‐shift keying signal verifies the high‐performance routing capability of this chip. These results indicate that the large‐scale optical switch with broadband, low crosstalk, and high‐power efficiency is promising for datacenter optical network applications. [ABSTRACT FROM AUTHOR]

Programmable photonic circuits require an electronic control layer to configure and stabilize the optical functionality at run‐time. Such control action is normally implemented by supervising the status of the circuit with integrated light monitors and by providing feedback signals to integrated actuators. This paper demonstrates that the control action can be effectively performed with electrical signals that are time‐multiplexed directly on the photonic chip. To this aim, the necessary electronic functionalities are monolithically integrated in a conventional 220 nm silicon photonics platform with no changes to the standard fabrication process. By exploiting a non‐conventional structure to implement metal‐oxide–semiconductor field‐effect transistors, an electronic controller is co‐designed into a programmable photonic circuit to enable a time‐multiplexed readout of integrated photodetectors and sequential activation of thermal phase shifters with on‐chip electronic memory. The accuracy of the time‐multiplexed control, achieved on a time scale of less than 10 ms, is demonstrated by penalty‐free routing of 10 Gbit s−1 modulated signals. This approach can be straightforwardly applied to large‐scale photonic chips to reduce the number of required electrical input/output connections. [ABSTRACT FROM AUTHOR]

Terahertz (THz) metasurfaces have emerged as powerful tools to modulate the wavefronts of THz radiation fully. Smart designs and fabrication are essential for enhancing the flexibility and encryption security of THz metasurfaces. In addition to digital coding metasurfaces and microelectromechanical systems, one method to realize dynamic THz metasurfaces is to utilize an active material. In this paper, a dynamic THz metasurface, which is combined with the phase‐change material VO2 and can be thermally controlled to achieve optical encryption, is proposed. Based on the electromagnetically induced transparency effect and by arranging the antennas in advance according to a specific hologram, a secret image can be encoded into the metasurface. At room temperature, the transmitted light field is an irregular light spot with no useful information. If the temperature increases above the phase‐change temperature, the encrypted hologram can be reconstructed. Moreover, owing to the distinct characteristics of VO2, the phase‐change temperature required during decryption is not very high, and the entire process is reversible. It is expected that, in combination with updated processing technology, such metasurfaces can be practically applied to the next generation of optical encryption or optical anticounterfeiting in the future. [ABSTRACT FROM AUTHOR]

Detecting the wavefront of photons in an efficient and accurate way is crucial to retrieve the information of an optical field. Liquid crystal (LC) possesses strong ability to manipulate the phase and polarization of photons with high diffraction efficiency and therefore offers a promising avenue toward this aim. In this paper, LC performing analog optical processing is explored and a computing LC platform is proposed to implement the wavefront sensing via tuned bias retardation. It is demonstrated that precisely introducing a tiny Pancharatnam–Berry phase by LC can achieve flexible separation of two spin components with high resolution. Modulating the retardation by rotation of an analyzer, the computing LC platform is used to reconstruct wavefronts with phase‐contrast patterns. In particular, combining this scheme with microscopy can precisely retrieve a micro‐scale phase distribution. The result suggests that the computing LC platform can perform as a wavefront sensor with high efficiency and may open up new opportunities in the applications of precision metrology, real‐time analog optical processing, and high‐contrast microscopy. [ABSTRACT FROM AUTHOR]

Lossy mode resonance (LMR) is an optical resonance phenomenon developed in the past decade, which has been researched for sensors and filters due to its high sensitivity, low loss, and broad tunable range. As a novel technology, if an analytical mathematical model for some fundamental questions like how to design the resonance wavelength, surrounding sensitivity, resonance width, and resonance depth, it will be guiding significance to its development. Herein, this paper develops a generalized Fabry–Perot resonance theory for LMR, where the oblique incidence, cavity loss, and dispersion of substrate and cavity are comprehensively considered, and the consistency of this model and a more rigorous guided wave optics model have been verified. Then, analytical mathematical models are established and analyzed, and the designing criterion for LMR‐based optical devices is proposed. After intensive reviewing the work of predecessors, the previous experimental results are consistent with the prediction of this model, and this model can also provide some new ideas that have not been researched yet. As an assistant to wave optics theory, this paper provides a second perspective to understand LMR phenomenon, and it is hoped the analytical solutions for LMR can be a guide for designing optical devices. [ABSTRACT FROM AUTHOR]

Photonic time stretch is the key enabling technology for a wide variety of instruments with unparalleled single‐shot data acquisition performance at high throughput and continuous operation. These systems have established landmark performance in spectroscopy and imaging including flow‐through microscopy, velocimetry, lidar, and other measurements. The evolution of the original time‐stretch technique into such diverse instruments and applications over the last 25 years has created the need for a unified theoretical framework. This paper represents the first step toward a universal mathematical model for time‐stretch instruments. It shows that the "stretch factor"—the fundamental performance metric—is governed by a single canonical equation in a wide range of seemingly diverse time‐stretch instruments. The paper also provides new insight into the operation of time‐stretch imaging and light scattering systems. The stretch factor is derived for time‐stretch systems that operate in temporal, spatial, angular, and Doppler domains. The analysis and mathematical tools provided here can facilitate understanding and analysis of such systems and help future developments in this field. [ABSTRACT FROM AUTHOR]

Mid‐infrared (IR) supercontinuum (SC) lasers are important in applications such as pollution detection, stand‐off detection, and non‐destructive testing. The performance in many applications is limited by the noise level of the supercontinuum laser. High noise typically results in low sensitivities or a need for long integration times. In this paper, a simple technique to reduce the noise of high noise soliton‐based SC sources is introduced by adding a short piece of normal dispersion fiber to force the spectrally distributed solitons to spectrally broaden through self‐phase modulation and thereby overlap to average out the noise. The noise reduction is demonstrated experimentally and numerically using a ZBLAN fiber based mid‐IR SC source and adding a short piece of highly nonlinear arsenic‐sulfide fiber. However, the method is generally applicable to any soliton‐based near‐IR or mid‐IR SC source. Its efficiency is underlined by experimentally comparing it to SC generation in fibers in which a second zero‐dispersion wavelength provides the spectral alignment noise reduction mechanism. [ABSTRACT FROM AUTHOR]

Recently, higher‐order topological insulators (HOTIs), accompanied by topologically nontrivial boundary states with a codimension larger than one, have been extensively explored because of unconventional bulk‐boundary correspondences. As a novel type of HOTIs, very recent works have explored the square‐root HOTIs, where the topologically nontrivial nature of bulk bands stems from the square of the Hamiltonian. In this paper, 2D square‐root HOTIs are experimentally demonstrated in photonic waveguide arrays written in glass using femtosecond laser direct‐write techniques. Edge and corner states are clearly observed at visible light spectra. The dynamical evolutions of topological boundary states are experimentally demonstrated, which verify the existence of photonic corner states in two band gaps. The symmetry‐protected corner states in the photonic square‐root HOTI may have potential applications in information processing and lasing. [ABSTRACT FROM AUTHOR]

Resonance optical fiber sensors are widely studied for their high sensitivity, small size, and anti‐electromagnetic interference. However, traditional resonance optical fiber sensors have encountered bottlenecks in the trace detection due to limited localized field intensity and low molecules affinity. With the development of materials technology, low‐dimensional materials such as quantum dots, graphene, and transition metal sulfides have excellent properties such as high carrier mobility, large specific surface area, and flexible structure controllable artificial technologies that can also be used to synthesize new materials with desired characteristics, which can enhance the performance of sensors fundamentally. The introduction of low‐dimensional materials can not only achieve the performance optimization of sensors, but also make sensors functional to realize the diversification of detection objects. This paper reviews the research progress of resonance optical fiber sensors based on low‐dimensional materials. The detection principle and performance indexes related to resonance optical fiber sensing are elaborated, and resonance optical fiber sensors modified by low‐dimensional materials are introduced. Furthermore, the role of low‐dimensional materials in resonance fiber sensing is summarized, the direction of performance optimization in the production process of resonance fiber sensors is analyzed, and the future prospect of new resonance optical fiber sensors is given. [ABSTRACT FROM AUTHOR]

Thin‐film lithium‐niobate photonics has attracted intensive attention due to its superior material properties. In particular, multimode lithium‐niobate photonics is becoming attractive for the applications of high‐capacity optical interconnects and high‐efficiency nonlinear optics. However, multimode manipulation in lithium‐niobate‐on‐insulator (LNOI) waveguides is not easy because there might occur some mode hybridness due to the vertical asymmetry as well as the material anisotropy. In this paper, high‐performance mode‐multiplexing devices with anisotropic LNOI waveguides are proposed, consisting of a multi‐channel mode (de)multiplexer and a sharp multimode waveguide bend (MWB). The mode (de)multiplexer is designed with Z‐propagation LNOI waveguides to avoid the mode hybridness. Meanwhile, the sharp MWB is designed to connect with a Y‐propagation waveguide, enabling access to the highest electro‐optic coefficient and second‐order nonlinear coefficient. The fabricated mode (de)multiplexer has a low excess loss less than 0.2 dB as well as low crosstalk less than ‐19 dB in the wavelength range of 1520–1600 nm. These high‐performance multimode photonic devices are useful for developing multimode LN photonics. [ABSTRACT FROM AUTHOR]

Optically active defects in diamond are widely used as bright single-photon sources for quantum sensing, computing, and communication. For many applications, it is useful to place the emitter close to the diamond surface, where the radiative properties of the emitter are strongly modified by its dielectric environment. It is well-known that the radiative power from an electric dipole decreases as the emitter approaches an interface with a lower-index dielectric, leading to an increase in the radiative lifetime. For emitters in crystalline solids, modeling of this effect needs to take into account the crystal orientation and direction of the surface cut, which can greatly impact the emission characteristics. In this paper, a framework for analyzing the emission rates of shallow (< 100 nm) defects is provided, in which optical transitions are derived from electric dipoles in a plane perpendicular to their spin axis. The calculations for the depth-dependent radiative lifetime for color centers in (100)-, (110)-, and (111)-cut diamond are presented, which can be extended to other vacancy defects in diamond. [ABSTRACT FROM AUTHOR]

The polarization beam splitter (PBS) is a pivotal element in the polarization management of free-space optical instruments and systems. Photonic integrated circuits for sensing, imaging, communications, and quantum-information processing also have needs for monolithically integrated PBSs with an ultra-broad optical bandwidth. In this paper, a novel silicon nanophotonic PBS inspired by the crystalline Glan-Thompson prism but implemented with silicon subwavelength-grating (SWG) metamaterials is presented. Due to the tailored artificial anisotropy of SWGs, the meta-prism functions like a thin-film reflector or a waveguide crossing for different polarizations. Thus, the incident light can be steered with strong polarization selectivity and negligible wavelength dependence. Unlike conventional PBS designs, the routing of polarized light is enabled by the wavelengthindependent total internal reflection in anisotropy-engineered effective media, thereby breaking the bandwidth limit. The device footprint is as small as ≈15 x 7 υm². Low insertion losses of 0.6-1.7 dB and high extinction ratios of 20-30 dB are experimentally achieved spanning a record broad bandwidth of over 415 nm, ranging from 1.26 to 1.675 μm wavelength. These results represent, to the best of their knowledge, the most broadband integrated PBS ever demonstrated to date. [ABSTRACT FROM AUTHOR]

Reliable remote pressure readout is possible only if high sensitivity of the measurement and independence from other physical factors are ensured. Among the parameters most strongly affecting measurements, temperature plays the most important role. In luminescence manometry, ratiometric measurement facilitates rapid pressure measurement ensuring high sensitivity of measurement while maintaining accuracy. Therefore, this paper compares the manometric performance of two ratiometric approaches in the material based on the luminescence of Cr3+ ions: using the intensity ratio of 2E→4A2 to 4T2→4A2 and a new approach based on the luminescence intensity ratio of 4T2→4A2 band recorded in two spectral ranges. Using the first approach, a manometer with an unprecedented sensitivity of SR = 40% GPa-1 is developed. However, the second approach provides completely temperature-invariant pressure measurement with a sensitivity of SR = 9.8% GPa-1. The presented results indicate that the MgO:Cr3+ nanoparticles are a highly reliable and sensitive candidate for a new luminescent manometer. [ABSTRACT FROM AUTHOR]

Integrated magneto-optic (MO) modulators are an attractive but not fully explored alternative to electro-optic (EO) modulators. They are current driven, structurally simple, and could potentially achieve high efficiency in cryogenic and room temperature environments where fJ bit-1 optical interfaces are needed. In this paper, the performance and energy efficiency of a novel MO modulator at room temperature are for the first time assessed. First, a model of the micro-ring-based modulator is implemented to investigate the design parameters and their influence on the performance. Then, a fabricated device is experimentally characterized to assess its performance in terms of bit rate and energy efficiency. The model shows efficient operation at 1.2 Gbps using a 16 mA drive current, consuming only 155 fJ bit-1. The experimental results show that the MO effect is suitable for modulation, achieving error-free operation above 16 mA with a power consumption of 258 fJ bit-1 at a transient limited data rate of 1.2 Gbps. [ABSTRACT FROM AUTHOR]

The quest for ever-shorter optical pulses has been ongoing for over half a century. Although few-cycle pulses have been generated for nearly 40 years, pulse lengths below the single-cycle limit have remained an elusive goal for a long time. For this purpose, optical waveform synthesizers, generating high-energy, high-average-power pulses via coherent combination of multiple pulses covering different spectral regions, have been recently developed. They allow unprecedented control over the generated optical waveforms, spanning an extremely broad spectral range from ultraviolet to infrared. Such control allows for steering strong-field interactions with increased degrees of freedom. When driving high-harmonic generation, tailored waveforms can produce bright attosecond pulse trains and even isolated attosecond pulses with tunable spectra up to the soft X-ray range. In this paper recent progress on parametric and hollow-core fiber waveform synthesizers is discussed. Newly developed seeding schemes; absolute, relative, and spectral phase measurement; and control techniques suitable for synthesizers are described. The progress on serial and parallel waveform synthesis based on Ti:sapphire and Ytterbium laser systems and their latest applications in high-harmonic generation in gaseous and solid media, attosecond science, and laser wakefield acceleration is discussed. [ABSTRACT FROM AUTHOR]

Recently, silicon-integrated optical circuits have attracted intensive interests, thanks to the compatibility with the complementary metal-oxide-semiconductor (CMOS) technology that enables mass production at low cost. The optical switch is an essential part of optical integrated circuits, with broad applications in optical communications and networks, optical computing, and sensing such as LiDAR. In general, the silicon-integrated optical switch adopts thermo-optic or carrier dispersion effect to realize reconfigurable signal routing. However, the use of thermo-optic effect leads to high power consumption, and the carrier dispersion effect has the disadvantage of small refractive index change. In addition, both effects are non-latching, and hence, continuous power consumption is required even when switching is not needed. For overcoming these drawbacks, phase-change materials (PCMs) have been introduced into silicon-integrated optical switches. In this paper, silicon-integrated optical switches are classified according to the underlying structure and recent research is reviewed. Recent studies on silicon-integrated optical switches incorporating PCMs are also reviewed. Furthermore, the pros and cons of different types of integrated optical switches with and without PCMs are compared and discussed. [ABSTRACT FROM AUTHOR]

Dispersion is one of the key performances of optical systems. As a man‐made device, metasurface is a notable alternative for dispersion manipulation and has been developed vigorously in recent years. However, the currently reported dispersion manipulation principle of meta‐atoms only relies on controlling the propagation phase in the operation frequency band or several working wavelengths. In this paper, the chirality‐assisted phase is introduced as an additional degree of freedom to engineer the dispersion characteristics of the meta‐atom, and the strategy is theoretically demonstrated. The dispersion characteristic of the chiral meta‐atom working in a reflective manner is discussed in detail within the working bandwidth. Then, two hybrid dispersion‐engineered metamirrors (HDEMs) are proposed and constructed to demonstrate versatile dispersion manipulation in the working frequency band, including achromatic focusing for the lower half band and hyper dispersive focusing for the upper half band, and hyper dispersive focusing and abnormal dispersive focusing in the lower and upper half band, respectively. Both full‐wave simulation and measured performances verify the validity and flexibility of the proposed strategy. This work exploits a new degree of freedom for dispersion manipulation, providing a new approach for dispersion‐engineered metasurfaces design. [ABSTRACT FROM AUTHOR]

Integrated photonic devices operating via optical nonlinearities offer a powerful solution for all‐optical information processing, yielding processing speeds that are well beyond that of electronic processing as well as providing the added benefits of compact footprint, high stability, high scalability, and small power consumption. The increasing demand for high‐performance nonlinear integrated photonic devices has facilitated the hybrid integration of novel materials to address the limitations of existing integrated photonic platforms. Recently, graphene oxide (GO), with its large optical nonlinearity, high flexibility in altering its properties, and facile fabrication processes, has attracted significant attention, enabling many hybrid nonlinear integrated photonic devices with improved performance and novel capabilities. This paper reviews the applications of GO to nonlinear integrated photonics. First, an overview of GO's optical properties and the fabrication technologies needed for its on‐chip integration is provided. Next, the state‐of‐the‐art GO nonlinear integrated photonic devices are reviewed, followed by comparisons of the nonlinear optical performance of different integrated platforms incorporating GO as well as hybrid integrated devices including different kinds of 2D materials. Finally, the current challenges and future opportunities in this field are discussed. [ABSTRACT FROM AUTHOR]

Structured lights, including beams carrying spin and orbital angular momenta, radially and azimuthally polarized vector beams, as well as spatiotemporal optical vortices, have attracted significant interest due to their unique amplitude, phase front, polarization, and temporal structures, enabling a variety of applications in optical and quantum communications, micromanipulation, and super‐resolution imaging. In parallel, structured optical materials, metamaterials, and metasurfaces consisting of engineered unit cells—meta‐atoms, opened new avenues for manipulating the flow of light and optical sensing. While several studies explored structured light effects on the individual meta‐atoms, their shapes are largely limited to simple spherical geometries. However, the synergy of the structured light and complex‐shaped meta‐atoms has not been fully explored. In this paper, the role of the helical wavefront of Laguerre–Gaussian beams in the excitation and suppression of higher‐order resonant modes inside all‐dielectric meta‐atoms of various shapes, aspect ratios, and orientations, is demonstrated and the excitation of various multipolar moments that are not accessible via unstructured light illumination is predicted. The presented study elucidates the role of the complex phase distribution of the incident light in shape‐dependent resonant scattering, which is of utmost importance in a wide spectrum of applications ranging from remote sensing to spectroscopy. [ABSTRACT FROM AUTHOR]