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The traditional computer with von Neumann architecture has the characteristics of separate storage and computing units, which leads to sizeable time and energy consumption in the process of data transmission, which is also the famous "von Neumann storage wall" problem. Inspired by neural synapses, neuromorphic computing has emerged as a promising solution to address the von Neumann problem due to its excellent adaptive learning and parallel capabilities. Notably, in 2016, researchers integrated light into neuromorphic computing, which inspired the extensive exploration of optoelectronic and all-optical synaptic devices. These optical synaptic devices offer obvious advantages over traditional all-electric synaptic devices, including a wider bandwidth and lower latency. This review provides an overview of the research background on optoelectronic and all-optical devices, discusses their implementation principles in different scenarios, presents their application scenarios, and concludes with prospects for future developments. [ABSTRACT FROM AUTHOR]

Binocular stereo vision relies on imaging disparity between two hemispherical retinas, which is essential to acquire image information in three dimensional environment. Therefore, retinomorphic electronics with structural and functional similarities to biological eyes are always highly desired to develop stereo vision perception system. In this work, a hemispherical optoelectronic memristor array based on Ag‐TiO2 nanoclusters/sodium alginate film is developed to realize binocular stereo vision. All‐optical modulation induced by plasmonic thermal effect and optical excitation in Ag‐TiO2 nanoclusters is exploited to realize in‐pixel image sensing and storage. Wide field of view (FOV) and spatial angle detection are experimentally demonstrated owing to the device arrangement and incident‐angle‐dependent characteristics in hemispherical geometry. Furthermore, depth perception and motion detection based on binocular disparity have been realized by constructing two retinomorphic memristive arrays. The results demonstrated in this work provide a promising strategy to develop all‐optically controlled memristor and promote the future development of binocular vision system with in‐sensor architecture. [ABSTRACT FROM AUTHOR]

The hardware‐level construction of artificial synapses, mimicking the functionality of biological synapses, is widely acknowledged as a pivotal stride in artificial intelligence systems. Particularly, establishing all‐optical artificial synapses for neuromorphic computing, leveraging on‐chip optical interconnects instead of conventional wired connections, has garnered widespread attention. Here, high‐quality CsPbBr3 single crystals are synthesized, and intriguing relaxation processes associated with reversible photo‐induced phase transition (PIPT) are observed, leading to a corresponding change in the birefringence effect. The birefringence change is systematically analyzed by an optical system. The relaxation time of reversible PIPT is similar to the behavior patterns of biological synapses, enabling the device to mimic synaptic features. The device successfully mimics excitatory/inhibitory synaptic behaviors such as EPSP/IPSP, PPF, SDDP, SFDP, and SIDP by using 1310 nm signal. Furthermore, the device continues to exhibit excitatory/inhibitory synaptic functionality when 940 and 1550 nm signals are applied, achieving multi‐wavelength synaptic behaviors. The all‐optical devices have the advantages of low crosstalk, fast signaling, and wide optical bandwidth, which lays the foundation of all‐optical hardware for neuromorphic computing systems. [ABSTRACT FROM AUTHOR]

All-optical tunability of semiconductor metasurfaces offers unique opportunities for novel time-varying effects, including frequency conversion and light trapping. However, the all-optical processes often induce optical absorption that fundamentally limits the possible dynamic increase of their quality factor (Q-boosting). Here, we propose and numerically demonstrate the concept of large Q-boosting in a single-material metasurface by dynamically reducing its structural anisotropy on a femtosecond timescale. This balance is achieved by excitation with a structured pump and takes advantage of the band-filling effect in a GaAs direct-bandgap semiconductor to eliminate the free-carrier-induced loss. We show that this approach allows a dynamic boosting of the resonance quality factor over orders of magnitude, only limited by the free-carrier relaxation processes. The proposed approach offers complete dynamic control over the resonance bandwidth and opens applications in frequency conversion and light trapping. [ABSTRACT FROM AUTHOR]

All‐optical modulation plays a key role in next‐generation optical processing and has attracted enormous attention worldwide. With extraordinary optoelectronic characteristics and friendly integration compatibility with various nanostructures, graphene shows great potential for ultrafast and energy‐efficient all‐optical modulation. Here, high‐efficiency on‐chip all‐optical modulation is experimentally demonstrated based on ultra‐thin silicon/graphene hybrid waveguides, which are complementary‐metal‐oxide‐semiconductor‐compatible and easy to fabricate. Owing to the enhanced light‐graphene interaction enabled by the ultra‐thin silicon photonic platform, the optical nonlinear absorption in graphene is greatly enhanced and a modulation depth of >2 dB is achieved with a saturation threshold of 0.9 pJ per pulse for a 50‐µm‐long modulator. The measured modulation efficiency is as high as 0.052 dB µm−1. Furthermore, the proposed all‐optical modulator has the potential to operate at a bandwidth of hundreds of gigahertz. The present hybrid integration of graphene on ultra‐thin silicon photonic waveguides paves the way toward the applications of on‐chip ultrafast and energy‐efficient all‐optical information processing. [ABSTRACT FROM AUTHOR]

The control of information is a defining feature of the information age, and the optical modulator likewise has a crucial role in optical networks. The transmission, processing, and storage of data have demanded low energy consumption and high speed for photonic systems, promoting the development of electro-optic modulators to all-optical modulators. Although these all-optical modulation methods eliminate the photoelectric conversion, the disadvantage of volatile materials requiring continuous power supply when processing and retaining data in new materials-based devices increase energy consumption. We propose a Ge2Sb2Te5 (GST) integrated all-optical, nonvolatile optical modulator for in-fiber operation. The pulse-induced GST phase transition changes the reflectivity of the fiber end face, and this difference affects the result of the interference, achieving a modulation of output light intensity in interference spectra. The experimental results reveal that the device has obtained 13 dB interference intensity contrast in the telecommunications bands, and its response to a pump pulse is around 100 ns. Furthermore, we demonstrated the operation of the device as a scalar multiplication unit and a logic operation unit. The signal can be transmitted, processed, and stored in the fiber without photoelectric conversion. With the benefits of the switching power consumption of less than 100 nJ and the nonvolatile nature of GST, the device will be more energy-efficient in synchronous processing and storing. This in-fiber operating modulator lays the foundation for developing all-optical devices and networks.

With the advantage of high bandwidth, low power consumption, and low crosstalk from optical signal stimulation, optoelectronic synapses are attracting more and more attention. Herein, a self‐powered two‐terminal optoelectronic synapse based on a lead‐free Cs2AgBiBr6 perovskite/P(VDF‐TrFE)/pentacene heterostructure is designed, which shows bidirectional responses to optical stimuli with different wavelengths (λ = 445 nm/660 nm). This feature enables the device to emulate both excitatory and inhibitory synaptic behaviors in a fully optical pathway. Besides optical stimulus, humidity is used as an additional stimulus to modulate the synaptic performance of the device under 445 nm illumination. The device is successfully applied to stimulate the behavior of the weather tree forecast and visual learning and forgetting processes under different mood states via humidity regulation. [ABSTRACT FROM AUTHOR]

The family of 2D transition metal carbides, nitrides, and carbonitrides (MXenes) has attracted an enormous amount of attention due to their tunable optical, electronic, electrochemical, and mechanical properties. Recently, a new branch of MXenes materials research has emerged that is exploring and engineering the intrinsic optical response of MXenes, resulting in compact nonlinear optical (NLO) devices. As a novel 2D materials system, MXenes not only exhibit common advantages of classical 2D materials for NLO applications but also demonstrate their unique superiority, such as high yield and scalable synthesis, good stability, switchable NLO response, etc. Here, a fundamental overview of MXenes nonlinear optics is provided, covering everything from MXenes synthesis to linear and NLO properties and NLO applications. The synthesis method and its influence on the MXenes structures and morphology are discussed, which dominated the linear optics of MXenes. Then, the third‐order NLO properties and carrier dynamics of MXenes, from basic theory to experimental results, are elaborated. Their NLO applications, including ultrashort laser pulse, single‐frequency laser generation, all‐optical phase modulation, wavelength modulation, and passive photonic diodes, are also highlighted. Finally, the current challenges and an outlook for future MXenes NLO research are proposed. [ABSTRACT FROM AUTHOR]

To explain the phenomenon of all-optical modulation of quantum cascade laser (QCL), and explore the physics in QCL’s gain medium which consists of multiple of dielectric nanostructures with high refractive index under light injection, we modified the 1½-period model to calculate values of electron population and lifetime in each subband which is separated by the nanostructures, optical gain, current and number of photons in the cavity of a mid-infrared QCL modulated with near-infrared optical injection. The results were consistent with an experiment, where the injected light increases the electron population and lifetime, but does not affect the optical gain obviously. Our study can be helpful for optimizing its use and dielectric nanostructure design.

All-optical modulators play a key role in building all-optical networks for efficient optical signal processing and have attracted intensive attention. In this paper, all-optical modulators with in situ grown molybdenum telluride (MoTe2) nanosheets on silicon are proposed and demonstrated for the first time with a self-developed complementary-metal-oxide-semiconductor (CMOS)-compatible fabrication processes. For the silicon-based all-optical modulators with a MoTe2-integrated microring resonator and microdisk resonator, the modulation is as efficient as 17.76 and 158.48 pm/mW while the rise/fall time is 3.7/3.6 and 1.5/3.3 μs, respectively. This is the highest tuning efficiency and the fastest response speed among all-optical silicon modulators based on the photothermal effect of two-dimensional materials under the out-of-plane pumping configuration. Furthermore, the manufacturing processes of the present devices are developed from in situ grown MoTe2 nanosheets on a silicon-on-insulator platform, which is CMOS-compatible, stable, and suitable for large-scale photonic integration. [ABSTRACT FROM AUTHOR]

In this manuscript, an all-optical modulation photodetector based on a CdS/graphene/Ge sandwich structure is designed. In the presence of the modulation (near-infrared) light, the Fermi level of the graphene channel shifts, allowing for the tuning of the visible light response speed as well as achieving a broad responsivity range from negative (-3376 A/W) to positive (3584 A/W) response. Based on this, logical operations are performed by adjusting the power of the modulation light superimposed with the signal light. This facilitates more covert, all-optical, high-speed encrypted communication. The ultrahigh tunability and nearly symmetric positive and negative photoconductivity of all-optical modulation photodetectors significantly enhance the computational capacity of neuromorphic hardware. The proposed device exhibits substantial advantages in applications requiring high fault tolerance for integrated sensing-computing （ISC） and high-resolution motion object recognition, providing insights for the development of next-generation high-bandwidth, low-power-consumption ISC devices., (© 2025 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Photo-modulation is a promising strategy for contactless and ultrafast control of optical and electrical properties of photoactive materials. Graphene is an attractive candidate material for photo-modulation due to its extraordinary physical properties and its relevance to a wide range of devices, from photodetectors to energy converters. In this review, we survey different strategies for photo-modulation of electrical and optical properties of graphene, including photogating, generation of hot carriers, and thermo-optical effects. We briefly discuss the role of nanophotonic strategies to maximize these effects and highlight promising fields for application of these techniques.

A strong nonlinear optical response of 2D MoSe2 nanoflakes (NFs) through spatial self‐phase modulation (SSPM) and cross‐phase modulation (XPM) induced by nonlocal coherent light–matter interactions is reported. The coherent interaction of light and MoSe2 NFs creates the SSPM of laser beams, forming concentric diffraction rings. The nonlinear refractive index (n2) and third‐order broadband nonlinear optical susceptibility (χ(3)) of MoSe2 NFs are determined from the self‐diffraction pattern at different exciting wavelengths of 405, 532, and 671 nm with varying laser intensity. The evolution and deformation of diffraction ring patterns are observed and analyzed by the "wind‐chime" model and thermal effect. By taking advantage of the reverse saturated absorption of 2D SnS2 NFs compared to MoSe2, an all‐optical diode has been designed with MoSe2/SnS2 hybrid structure to demonstrate the nonreciprocal light propagation. Few other optical devices based on MoSe2 and semiconducting materials such as Bi2Se3, CuPc, and graphene have been investigated. The all‐optical logic gates and all‐optical information conversion have been demonstrated through the XPM technique using two laser beams. The proposed optical scheme based on MoSe2 NFs has been demonstrated as a potential candidate for all‐optical nonlinear photonic devices such as all‐optical diodes and all‐optical switches. [ABSTRACT FROM AUTHOR]

2D atomically thin graphdiyne oxide (GDYO) nanosheets (NSs) are synthesized, and their nonlinear modulation is investigated. Generally, improving the modulation depth (MD) of all‐optical modulation (AOM) requires a pump light with strong power, which limits the development of AOM technology in the design of low‐power loss devices. In this study, an AOM system based on spatial self‐phase modulation and spatial cross‐phase modulation methods is proposed using 2D GDYO NSs. The results reveal that 2D GDYO exhibits tunable nonlinearity and high stability, which is desirable for designing the AOM system. Because of the excellent optical properties of 2D GDYO, a large MD of >98% is achieved for the proposed AOM with a low power of pump light, which is higher than most AOMs currently reported. Thus, GDYO is an excellent modulation material in AOM, which improves the application prospects of carbon nanomaterials in all‐optical devices. [ABSTRACT FROM AUTHOR]

Active metasurfaces, in which the optical property of a metasurface device can be controlled by external stimuli, have attracted great research interest recently. For optical switching and modulation applications, high-performance active metasurfaces need to show high transparency, high power efficiency, as well as ultrafast switching and large-scale fabrication capability. This paper reports Au/VO2-based active metasurfaces meeting the requirements above. Centimeter-scale Au/VO2 metasurfaces are fabricated by polystyrene sphere colloidal crystal self-assembly. The devices show optical modulation on-off ratio up to 12.7 dB and insertion loss down to 3.3 dB at 2200 nm wavelength in the static heating experiment, and ΔT/T of 10% in ultrafast pump-probe experiments. In particular, by judiciously aligning the surface plasmon resonance wavelength to the pump wavelength of the femtosecond laser, the enhanced electric field at 800 nm is capable to switch off the extraordinary optical transmission effect at 2200 nm in 100 fs time scale. Compared to VO2 thin-film samples, the devices also show 50% power reduction for all-optical modulation. Our work provides a practical way to fabricate large-scale and power-efficient active metasurfaces for ultrafast optical modulation.

We demonstrate all-optical modulation with a near-unity contrast of nonlinear light generation in a dielectric metasurface. We study third-harmonic generation from silicon Fano-resonant metasurfaces excited by femtosecond pulses at 1480 nm wavelength. We modulate the metasurface resonance by free carrier excitation induced by absorption of an 800 nm pump pulse, leading to up to 93% suppression of third-harmonic generation. Modulation and recovery occur on (sub)picosecond time scales. According to the Drude model, the pump-induced refractive index change blue-shifts the metasurface resonance away from the generation pulse, causing a strong modulation of third-harmonic conversion efficiency. The principle holds great promise for spatiotemporal programmability of nonlinear light generation.

Due to the existence of surface plasmon resonances, enormous nonlinear optical effects are generated by plasmonic nanostructures, leading to the trend in which these nanostructures have gradually become ideal platforms for all‐optical manipulations. Here, it is discovered that an anomaly of the relationship between the sample reflectance and the pump‐light polarization angle occurs at the localized surface plasmons mode. Relatively, normal relationships exist at the interband transition and the propagating surface plasmon polaritons mode. Furthermore, electrical‐field enhancements are intentionally acquired by solely keeping either the pump beam or the probe beam on, so that the anomaly‐governing mechanism is identified as the aggregation of hot electrons within the probe‐detected sensitivity zone. The discovery of this anomaly and the associated mechanism can be applied to ultrafast all‐optical communications, computing, and the design of photonics‐related devices. [ABSTRACT FROM AUTHOR]

• All-optical tunning is fascinating for its simplicity and efficiency. • All-optical modulation in a silica microsphere can be extended to all-bands. • Modulation in a silica microsphere can reach over 15 dB extinction ratio. • Multi-format modulation can be used in communication and microwave photonics. We propose and demonstrate an all-optical tunable silica microsphere resonator based on a dual-laser pumping scheme. The resonance tunable microsphere resonator can act as a modulator and operates in the O-band. We discussed the relationship between the extinction ratio and pump power in different coupling state, and realized an extinction ratio over 15 dB. Also, we measured the rise and fall time of the modulated signal, which is below 1 μs, and discussed its relationship with the modulation frequency. In addition, based on this scheme, a multi-format modulation is realized for the first time with signals shaping in triangular, sinusoidal and square wave under different duty cycles. Our work reveals the detail of all-optical tunning of the resonance of the silica microresonator and opens up possible applications in optical communication, microwave photonics and quantum photonics. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically and experimentally investigate the all-optical modulation characteristics of a microfiber coupler combined Sagnac loop (MCSL). We inject pump lights with different intensities into the MCSL and utilize the thermo-optical effect from the microfiber coupler to control the phase relationship between the counter-propagating beams inside the Sagnac loop. The spectral characteristics from the Sagnac loop can be controlled accordingly, and the rate of the frequency comb (interference characteristic wavelength) shift can be 1 pm/mW. In addition, at a specific wavelength (e.g., 1550 nm), the MCSL can be used as an intensity modulator as well as a reflectivity-tunable Sagnac reflector. The reflectivity variation of the Sagnac reflector can reach about 10% when the pump light is at milliwatt level. The intensity modulation depth can be 9.3% at 100 Hz when the intensity-modulated 980 nm pump light imposed on the MCSL is 5.5 mW. Based on the thermo-optical effect, the MCSL can achieve the all-optical intensity modulation and all optically tunable filtering functions. The device is expected to play an important role in the development of tunable, multi-wavelength, and compact fiber lasers.

Active metasurfaces, in which the optical property of a metasurface device can be controlled by external stimuli, have attracted great research interest recently. For optical switching and modulation applications, high-performance active metasurfaces need to show high transparency, high power efficiency, as well as ultrafast switching and large-scale fabrication capability. This paper reports Au/VO2-based active metasurfaces meeting the requirements above. Centimeter-scale Au/VO2 metasurfaces are fabricated by polystyrene sphere colloidal crystal self-assembly. The devices show optical modulation on-off ratio up to 12.7 dB and insertion loss down to 3.3 dB at 2200 nm wavelength in the static heating experiment, and ΔT/T of 10% in ultrafast pump-probe experiments. In particular, by judiciously aligning the surface plasmon resonance wavelength to the pump wavelength of the femtosecond laser, the enhanced electric field at 800 nm is capable to switch off the extraordinary optical transmission effect at 2200 nm in 100 fs time scale. Compared to VO2 thin-film samples, the devices also show 50% power reduction for all-optical modulation. Our work provides a practical way to fabricate large-scale and power-efficient active metasurfaces for ultrafast optical modulation. [ABSTRACT FROM AUTHOR]

Dynamically manipulating highly intense ultrafast pulses by optical modulators is extremely useful for strong‐field physics. However, the manipulation has been severely restricted by the fundamental drawbacks of most modulators such as the low laser damage threshold and high energy consumption. Here, the implementation of an all‐optical modulator on femtosecond lasers up to 1011 W cm−2 covering wavelengths from 1.6 to 2.3 µm is demonstrated; the modulator is controlled by a weak continuous‐wave laser (≈103 W cm−2) based on the prominent plasmon‐assisted thermo‐optic nonlinearity of suspended antimonene quantum dots (AQDs). The strong localization of the surface plasmon of the AQDs contributes a tremendous effective nonlinear refractive index (n2 ≈ 10−5 cm2 W−1) under weak light excitation, modulating the optical phase of copropagating intense lasers, and realizing robust "ON/OFF" alterations. It is also verified that the thermo‐optical effect occurs at a fast speed of ≈240 ps in this nanomaterial system. The findings provide new insight for exploiting the potential of plasmonic nonlinearities of nanomaterials, which offers a pragmatic and extensible solution to the urgent demand for manipulating and optical limiting of strong field physics in further nanophotonic platforms. [ABSTRACT FROM AUTHOR]

Boron nanosheets possess unique photoelectric properties, including photosensitivity, photoresponse, and optical nonlinearity. In this article, we show the interaction between light and boron nanosheets in which concentric rings formed in the far field, which attributed to the strong Kerr nonlinearity of boron nanosheets. Furthermore, the distortion, regulation and relationship between the Kerr nonlinearity and effective mass or carrier mobility of the diffraction rings of boron nanosheets have been investigated. Our work shows that the spatial self-phase modulation effect of boron nanosheets is indeed caused by nonlocal electronic coherence. In addition, we have implemented all-light modulation and all-light logic gates based on the prepared boron nanosheets. We believe that our results will provide a powerful demonstration of nonlinear photonic devices based on boron nanosheets and a reference for photonic devices based on two-dimensional materials. [ABSTRACT FROM AUTHOR]

All-optical devices, which are utilized to process optical signals without electro-optical conversion, play an essential role in the next generation ultrafast, ultralow power-consumption optical information processing systems. To satisfy the performance requirement, nonlinear optical materials that are associated with fast response, high nonlinearity, broad wavelength operation, low optical loss, low fabrication cost, and integration compatibility with optical components are required. Graphene is a promising candidate, particularly considering its electrically or optically tunable optical properties, ultrafast large nonlinearity, and high integration compatibility with various nanostructures. Thus far, three all-optical modulation systems utilize graphene, namely free-space modulators, fiber-based modulators, and on-chip modulators. This paper aims to provide a broad view of state-of-the-art researches on the graphene-based all-optical modulation systems. The performances of different devices are reviewed and compared to present a comprehensive analysis and perspective of graphene-based all-optical modulation devices. [ABSTRACT FROM AUTHOR]

Light-induced hot carriers in nanostructures and their corresponding optical nonlinearity have been extensively examined during the last decades. However, nonlinear optical effects dictated by the spatio-temporal evolution of out-of-equilibrium electrons at the nanoscale represent a much more recent research focus. Here we theoretically discuss the role of spatial inhomogeneities that energetic electrons feature across individual nanoantennas in metasurface configuration upon illumination with femtosecond laser pulses. As exemplary cases, we consider two-dimensional geometries of gold meta-atoms having either a high aspect ratio or a tapered cross-section and model their ultrafast optical response. A comparison with numerical results obtained either neglecting or accounting for spatial effects indicates that deep sub-wavelength spatio-temporal transients of carriers may have a significant impact on the dynamics of the all-optically modulated signal, with major quantitative corrections up to predicted changes in sign. Our results present hot-electron local inhomogeneities as an emerging subject with potentially relevant applications in various ultrafast nanophotonic configurations.

In this paper, we investigate the characteristics of all-optical modulation via thermo-optic effects of an optical microfiber coupler (OMC) and the theoretical analysis and experimental results are shown. The intensity modulation and the phase modulation efficiency are proportional to the length of the OMC' waist region, the pump light intensity, etc. We experimentally characterize the OMC, presenting that stable intensity and phase modulation can be realized by pumps at microwatts level. For OMC' intensity modulation, the modulation bandwidth is measured to be 50 kHz under 1.7 mW pump light intensity. We also demonstrate OMC's phase modulation function, and the frequency response characteristics of the OMC phase modulator shows similar properties with the OMC's intensity modulation, which mainly depends on the waveguide structures of the OMC' waist region and the heat conduction property of the waveguide materials. These results are valuable for the development of all-optical modulators and all-optical tunable filters based on subwavelength scales optical fiber, and hold great potential in laser and optical sensing applications.

We investigated and optimised the performance of the all-optical reflective modulation of the Mid-Wave Infrared (MWIR) signal by means of the optically-pumped sub-wavelength-structured optical membranes made of silicon. The membranes were optically pumped by a 60-femtosecond, 800-nm laser, while another laser operating in the MWIR ranging between 4 and 6 μ m was used to probe the optical response and modulation. We were able to achieve the conditions providing the modulation depth of 80% using the pump fluence of 3.8 mJ/cm 2 . To get a better insight into the performance and the modulation mechanism, we developed an optical model based on a combination of the Wentzel–Kramers–Brillouin approximation, Drude and Maxwell–Garnett theories. The model allowed us to estimate the values of the dielectric function, carrier concentration and scattering rate of the optically-excited membrane in the MWIR range. Using the model, we optimised the performance and found the conditions at which the reflective modulation can be operated with the ultrafast response of 0.55 ps and modulation contrast of 30%. [ABSTRACT FROM AUTHOR]

• The structure of the all-optical modulator based on graphene anti-resonant fiber (G-ARF) is proposed. • It can realize both modulation of long-wavelength to short-wavelength and modulation of short-wavelength to long-wavelength. • The experimental system for studying all-optical modulation characteristics of G-ARF is designed. • It provide a new method for graphene-based fiber all-optical modulator to achieve the ultrafast all-optical networks. We propose and investigate an all-optical modulator based on graphene anti-resonant fiber (G-ARF). G-ARF is fabricated by growth graphene on the hollow-core of silicon-based anti-resonant fiber. The all-optical modulation characteristics of G-ARF are studied at different wavelengths and all-optical modulator is prepared. Experimental results show that the G-ARF can realize all-optical modulation. The all-optical modulator has a modulation depth with 4.515 dB at the wavelength of 852 nm, and a modulation depth with 4.841 dB at the wavelength of 980 nm, when the pump light is amplified spontaneous emission (ASE) broadband light at the wavelength of 1550 nm. Moreover, the long-wavelength light source can be modulated using short-wavelength light source based on the proposed all-optical modulator. The modulation depths are 0.66 dB and 0.611 dB, respectively, when pump states quickly change between the on-state and the off-state. The proposed device will provide a new method for graphene-based fiber all-optical modulator and may be used to achieve the ultrafast all-optical networks and other applications. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the characteristics of all-optical modulation via thermo-optic effects of an optical microfiber coupler (OMC) and the theoretical analysis and experimental results are shown. The intensity modulation and the phase modulation efficiency are proportional to the length of the OMC' waist region, the pump light intensity, etc. We experimentally characterize the OMC, presenting that stable intensity and phase modulation can be realized by pumps at microwatts level. For OMC' intensity modulation, the modulation bandwidth is measured to be 50 kHz under 1.7 mW pump light intensity. We also demonstrate OMC's phase modulation function, and the frequency response characteristics of the OMC phase modulator shows similar properties with the OMC's intensity modulation, which mainly depends on the waveguide structures of the OMC' waist region and the heat conduction property of the waveguide materials. These results are valuable for the development of all-optical modulators and all-optical tunable filters based on subwavelength scales optical fiber, and hold great potential in laser and optical sensing applications. [ABSTRACT FROM AUTHOR]

Abstract: Metasurfaces have been widely used to manipulate terahertz waves due to their great potential for achieving unique electromagnetic responses. However, to realize ultrafast and efficient control of the light in active metasurfaces is still a critical challenge. Here, an ultrafast tunable metasurface which consists of ion‐implanted and annealed silicon disk array is experimentally demonstrated in the terahertz range. By utilizing the optical‐pump terahertz‐probe spectroscopy, the absolute transmission modulation up to 38% is realized at the electric dipole resonance under the femtosecond pulse excitation, with a switch‐on time within 20 ps and a recovery time of 300 ps. Furthermore, a theoretical analysis that quantitatively models the time dependence of the electron–hole plasma density and the permittivity of the silicon disks is proposed. Then, the transient transmission spectra of the metasurface are numerically simulated, which agree well with the experimental performances. The silicon‐based metasurface shows significant potential in ultrafast terahertz optics. [ABSTRACT FROM AUTHOR]

Pulse optimization and control are demonstrated in a standard middle-infrared quantum cascade laser by illuminating its front facet with two near-infrared lasers. The 1550- and 850-nm near-infrared lasers are used to optimize the pulse rise/fall time and the pulse shape, respectively, of the quantum cascade laser. Compared with the electric drive, the electron interband transition is directed by the all-optical approach. Simultaneously, the quantum cascade laser’s pulse width, amplitude, and repetition rate are controlled precisely by changing the two near-infrared lasers’ delay time, average power, and repetition rate. Such an all-optical approach is beneficial in the high-speed optimization and control of the quantum cascade laser pulse. It has the potential for application in free-space optical communication and high-speed frequency modulation spectroscopy. [ABSTRACT FROM AUTHOR]

• A polarization-independent, all-optically tunable multiband coherent perfect absorber (CPA) is designed and it can realize nearly 100% amplitude modulations at the telecommunication bands. • Bound states in the continuum (BICs) phenomenon observed in our proposed hybrid structure, remarkably high Q-factor peaks could be achieved. Insights into the BIC physical mechanisms have been provided. • Novel switches that can control the logical gate states have been realized at a specific wavelength via all-optically modulations based on the coherent perfect absorber (CPA). • The proposed coherent perfect absorber (CPA) with excellent tunable properties has great potential in many applications, such as optical switches, smart multi-band absorbers, logic devices and telecom devices in optics and communication systems. A polarization-independent, all-optically modulated multiband metamaterial coherent perfect absorber (CPA) is proposed. Numerical simulation results reveal that the absorber can be controlled over a wide range of amplitudes by changing the phase difference of two incident light beams. The all-optical modulation can be extended to telecom wavelengths, allowing for simultaneous modulation of absorption at 1310 nm and 1550 nm. In addition, switchable logical gate states can be achieved at the dip between absorption peaks. The proposed absorber utilizes bound states in the continuum (BIC) mode to realize another absorption band, expanding the application range and enhancing its flexibility. The results suggest that the proposed absorber has a promising modulated optical response, with potential applications in developing optical switches, smart multi-band absorbers, telecom devices and so on. [ABSTRACT FROM AUTHOR]

We investigated and optimised the performance of the all-optical reflective modulation of the Mid-Wave Infrared (MWIR) signal by means of the optically-pumped sub-wavelength-structured optical membranes made of silicon. The membranes were optically pumped by a 60-femtosecond, 800-nm laser, while another laser operating in the MWIR ranging between 4 and 6 μ m was used to probe the optical response and modulation. We were able to achieve the conditions providing the modulation depth of 80% using the pump fluence of 3.8 mJ/cm 2 . To get a better insight into the performance and the modulation mechanism, we developed an optical model based on a combination of the Wentzel−Kramers−Brillouin approximation, Drude and Maxwell−Garnett theories. The model allowed us to estimate the values of the dielectric function, carrier concentration and scattering rate of the optically-excited membrane in the MWIR range. Using the model, we optimised the performance and found the conditions at which the reflective modulation can be operated with the ultrafast response of 0.55 ps and modulation contrast of 30%.

The microscopic and semi-macroscopic mechanisms responsible for photoinduced mass transport in functionalized azo-polymers are far from deeply understood. To get some insight into those mechanisms on “microscopic” scale, we studied the directed photoinduced motion of single functionalized polymer chains under various types of polarized light illumination using Monte Carlo bond fluctuation model and our kinetic Monte Carlo model for photoinduced mass transport. We found sub-diffusive, diffusive and super-diffusive regimes of the dynamics of single chains at constant illumination and mostly super-diffusive regime for directed motion in the presence of the gradient of light intensity. This regime is more enhanced for long than for short chains and it approaches the ballistic limit for very long chains. We propose a physical picture of light-driven inscription of Surface Relief Gratings (SRG) as corresponding to a dynamical coexistence of normal and anomalous diffusion in various parts of the system. A simple continuous time random walk model of SRG inscription based on this physical picture reproduced the light-driven mass transport found in experiments as well as the fine structure of SRG.

Rabi splitting that arises from strong plasmon-molecule coupling has attracted tremendous interests. However, it has remained elusive to integrate Rabi splitting into the hybrid plasmon-waveguide modes (HPWMs), which have advantages of both subwavelength light confinement of surface plasmons and long-range propagation of guided modes in dielectric waveguides. Herein, we explore a new type of HPWMs based on hybrid systems of Al nanodisk arrays covered by PMMA thin films that are doped with photochromic molecules and demonstrate the photoswitchable Rabi splitting with a maximum splitting energy of 572 meV in the HPWMs by controlling the photoisomerization of the molecules. Through our experimental measurements combined with finite-difference time-domain (FDTD) simulations, we reveal that the photoswitchable Rabi splitting arises from the switchable coupling between the HPWMs and molecular excitons. By harnessing the photoswitchable Rabi splitting, we develop all-optical light modulators and rewritable waveguides. The demonstration of Rabi splitting in the HPWMs will further advance scientific research and device applications of hybrid plasmon-molecule systems. [ABSTRACT FROM AUTHOR]

We report the design of reconfigurable metamolecules consisting a large array of nanowire featuring U-shaped cross section. These nanoscale metamolecules support colocalized electromagnetic resonance at optical frequencies and mechanical resonance at GHz frequencies with a deep-subdiffraction-limit spatial confinement (-λ2/100). The coherent coupling of those two distinct resonances manifests a strong optical force, which is fundamentally different from the commonly studied forms of radiation forces, gradient forces, or photothermal induced deformation. The strong optical force acting upon the built-in compliance further sets the stage for allowing the metamolecules to dynamically change their optical properties upon the incident light. The all-optical modulation at the frequency at 1.8 GHz has thus been demonstrated experimentally using a monolayer of metamolecules. The metamolecules were conveniently fabricated using complementary metal-oxide-semiconductor-compatible metal deposition and nanoimprinting processes and thus offer promising potential in developing integrated all-optical modulator. [ABSTRACT FROM AUTHOR]

Optical computing with optical transistors has emerged as a possible solution to the exponentially growing computational workloads, yet an on-chip nano-optical modulation remains a challenge due to the intrinsically noninteracting nature of photons in addition to the diffraction limit. Here, we present an all-optical approach toward nano-excitonic transistors using an atomically thin WSe 2 /Mo 0.5 W 0.5 Se 2 heterobilayer inside a plasmonic tip-based nanocavity. Through optical wavefront shaping, we selectively modulate tip-enhanced photoluminescence (TEPL) responses of intra- and interlayer excitons in a ∼25 nm 2 area, demonstrating the enabling concept of an ultrathin 2-bit nano-excitonic transistor. We suggest a simple theoretical model describing the underlying adaptive TEPL modulation mechanism, which relies on the additional spatial degree of freedom provided by the presence of the plasmonic tip. Furthermore, we experimentally demonstrate a concept of a 2-trit nano-excitonic transistor, which can provide a technical basis for processing the massive amounts of data generated by emerging artificial intelligence technologies.

In this paper, nonlinear porous silicon based all-optical modulator is proposed and investigated by utilizing an asymmetrical Mach–Zehnder Interferometer (MZI) configuration consisted of two couplers with equal splitting ratio, and two unbalance arms, in which a porous silicon (PS) waveguide as the nonlinear element is only placed in one arm of MZI, and another arm is short fiber delay line. Results show that both a pulsed pump and continuous probe wave are simultaneously launched into the input port with the result that an outcome signal with ~14.10 dB modulation depth at probe wavelength is obtained at the end of the device under the conditions of an initial pulsed pump with 47.07 dB m peak, 10.88 extinction ratio and 100 ps duration, continuous probe wave of 0 dB m power, and 3-mm long PS waveguide. Extinction ratio and eye opening ratio of eye diagram are observed for various operation speeds. [ABSTRACT FROM AUTHOR]

An ultrafast all-optical modulator based on spherical quantum dot using electromagnetically induced transparency (EIT) technique in GaN/AlN structure, associated with inter-sublevel transitions, is proposed and analyzed. The aim of this paper is to modify and enhance the main parameters of an all-optical modulator such as, power consumption, modulation depth, maximum bit-rate and band-width. To realize these points, we have proposed a suitable quantum dot structure based on EIT in a strained GaN/AlN, with an internal barrier. Simulations show this barrier enhances the dot optical properties, such as dipole matrix element, linear susceptibility, and hence absorption coefficient, reducing the power consumption and increasing the modulation depth. Furthermore, using control signal in EIT process, carriers are driven from an upper state to a lower state from where they rapidly decay to the ground state increasing the modulation bit-rate and band-width. [ABSTRACT FROM AUTHOR]

Gain spectra of a three-well GaAs/AlGaAs quantum-cascade structure under interband pumping by ultrashort optical pulses are studied within the framework of the density matrix theory. A mathematical model for intersubband kinetics is derived taking into account many-body interactions and ultrafast interband optical pumping. It is found that pulsed interband pumping leads to an increase in intersubband gain by an order of magnitude, which is characterised by 1 ps rise time and 8 ps recovery time under pumping by 100 fs pulses with a peak intensity of 100 MW/cm2. Possible implementations of the concept are highlighted. The results uncover a new possibility for ultrafast switching of the material gain in quantum-cascade structures. [ABSTRACT FROM AUTHOR]

We review different techniques for modulation of the electromagnetic properties of terahertz (THz) waves. We discuss various approaches for electronic, optical, thermal and nonlinear modulation in distinct material systems such as semiconductors, graphene, photonic crystals and metamaterials. The modulators are classified and compared with respect to modulation speed, modulation depth and categorized by the physical quantity they control as e.g. amplitude, phase, spectrum, spatial and temporal properties of the THz wave. Based on the review paper, the reader should obtain guidelines for the proper choice of a specific modulation technique in view of the targeted application. [ABSTRACT FROM AUTHOR]

All-optical, low-power modulation is a major goal in photonics. Because of their high mode-field concentration and ease of manufacturing, nanoscale silicon waveguides offer an intriguing platform for photonics. So far, all-optical modulators built with silicon photonic circuits have relied on either two-photon absorption or the Kerr effect. Both effects are weak in silicon, and require extremely high (~5 W) peak optical power levels to achieve modulation. Here, we describe an all-optical Mach-Zehnder modulator based on a single-photon absorption (SPA) process, fabricated entirely in silicon. Our SPA modulator is based on a process by which a single photon at 1.55 mum is absorbed and an apparently free-carrier-mediated process causes an index shift in silicon, even though the photon energy does not exceed that of silicon's bandgap. We demonstrate all-optical modulation with a gate response of 1deg/mW at 0.5 Gb/s. This is over an order of magnitude more responsive than typical previously demonstrated devices. Even without resonant enhancement, further engineering may enable all optical modulation with less than 10 mW of gate power required for complete extinction, and speeds of 5 Gb/s or higher. [ABSTRACT FROM PUBLISHER]

This paper presents a theoretical analysis of a silicon all-optical modulator based on free-carrier injection by two-photon absorption (TPA) in a highly light-confining structure. In spite of the weak optoelectronic properties of silicon, strong light confinement allows high modulation depths in very compact devices requiring low-energy pump pulses. This analysis is applied to 1-5 mum radius silicon ring resonators with the pump pulse coupled on-chip and including in the model the scattering loss due to sidewall roughness originating from the fabrication process. The calculations show that using this scheme, modulation depths greater than 80% can be achieved, with no more than 3 pJ of pump pulse energy, at speeds on the order of 10 GHz [ABSTRACT FROM PUBLISHER]