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Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

A femtosecond mode-locked soliton erbium-doped fiber laser (EDFL) is demonstrated using a commercially available nonconductive graphene oxide paper as a saturable absorber. The paper that is sandwiched between two fiber ferrules acts as a mode-locker. The EDFL generates a soliton mode-locked pulse train with a repetition rate of 15.62 MHz and pulsewidth of 680 fs. It is observed that the fiber laser has a low pulsing threshold as well as low damage threshold. The pulse energy and peak power are 0.0085 nJ and 11.85 W, respectively. The easy fabrication of graphene oxide paper should promote its potential application in ultrafast photonics. [ABSTRACT FROM PUBLISHER]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

Describes the above-named upcoming special issue or section. May include topics to be covered or calls for papers. [ABSTRACT FROM AUTHOR]

The recent progress in III-nitride tunnel junction (TJ) contacts for optoelectronic devices is summarized in this review paper. Due to the rapid developments of various III-nitride based optoelectronic devices for different emerging applications, TJs are of interest for these devices to achieve more efficient device performance. This review paper first briefly describes the working principles of TJs and the advantages of employing TJs in optoelectronic devices. The significant advancements in III-nitride TJs realized by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are addressed, as well as their TJ device performances. Lastly, the critical challenges for employing III-nitride TJs in wide bandgap ultraviolet (UV) light emitters are discussed for future investigations. [ABSTRACT FROM AUTHOR]

This paper deals with the loss mechanisms in tunable vertical-cavity surface-emitting lasers (VCSELs). The strong increase of the threshold gain at the tuning range edges motivates the investigation of the degradation mechanisms presented in this paper. A campaign of simulations performed with our in-house VCSEL ELectroMagnetic (VELM) simulation code, combined with a novel approach based on the study of the Poynting vector, allowed to identify significant lateral radiation losses. The proposal of technology-affordable countermeasures rests on the proper understanding of these phenomena. [ABSTRACT FROM AUTHOR]

Provides a notice of upcoming special issue(s) of interest to practitioners and researchers. [ABSTRACT FROM PUBLISHER]

Inhomogeneous and random scattering in a static-scattering medium diffuses an incident light field into a complex speckle pattern. This phenomenon leads to uncontrolled and unpredictable changes in the spectrum as incident polychromatic light is scattered by the static-scattering medium. In this paper, we propose and demonstrate a novel technique for shaping the randomly scattered spectrum into a controlled mode. The proposed technique is demonstrated experimentally by examples of bandpass spectrum, stairs, right triangle, and Gaussian spectra. A theoretical model for simulating polychromatic light field passing through a scattering medium is also developed. Theoretical and experimental results are consistent. The findings of this paper may present exciting applications, such as compensation for fiber dispersion. [ABSTRACT FROM AUTHOR]

Quantum key distribution (QKD) relies on the laws of physics to establish a symmetric binary key between remote parties. A QKD link involves the realization of a quantum channel for the transmission of quantum key material encoded in certain photon properties, as well as a public channel for verification of the exchanged key material. This paper deals with the mutual dependence of these channels and analyzes the impact of performance of both channels on the overall key material establishment process. This paper presents measurement data obtained under laboratory conditions as well as the results obtained by establishing a virtual QKD link. Despite the common beliefs that increased quantum bit error rate implies a larger amount of traffic on the public channel, our measurements prove the opposite. The obtained data clearly show that the public channel has a major impact on the overall performance of the QKD link. [ABSTRACT FROM PUBLISHER]

Photonic Integrated Circuits (PICs) on indium phosphide have matured significantly over the past couple of decades and have found use in many system applications. Some PIC efforts on other group III-V substrates have also been initiated. In numerous cases, the usefulness of these PICs is because of the reduction in size, weight, and power they provide, but in many cases also because of the higher performance made possible by the improved relative phase stability among optical paths as well as the reduction of inter-element coupling losses. In this paper, as part of this special issue in tribute to Prof. Daniel Dapkus, we focus on monolithic PICs that provide a system function, especially those that incorporate and build on widely-tunable laser technology as a key element. Some of the early widely-tunable laser work is reviewed, and a selection of past system-on-a-chip developments is presented as background. Then, more recent system-on-a-chip advances performed by the author’s groups are reviewed in more detail. Key advances are highlighted. [ABSTRACT FROM AUTHOR]

The mainstream production of optoelectronic and electronic devices based on epitaxial III-V compound semiconductor materials largely employs metalorganic vapor phase epitaxy, a process first demonstrated for devices in the 1970’s. For this special issue in honor of Prof. P. Daniel Dapkus, this paper first briefly reviews his early contributions that spearheaded the interest of MOVPE as a III-V device epitaxy process. Next, the paper discusses MOVPE reactor development in the 1980’s, which at the time was one of the key challenges in establishing MOVPE technology as a reliable epitaxy manufacturing process. The approach combined physical modeling and numerical simulations of reactor processes followed by materials and device demonstrations. Highly uniform performance metrics of AlGaAs/AlGaAs quantum-well diode lasers and two-dimensional monolithic surface-emitting lasers were demonstrated with excellent run-to-run reproducibility. This foundational approach advanced efforts to standardize reactors and subsequent scaling for high-throughput production. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for designing dual-band absorbers based on graphene and metallic metasurfaces for terahertz and mid-infrared regimes, respectively. The absorbers are composed of a 2D array of square patches deposited on a dielectric film terminated by a metal plate. Using an analytical circuit model, we obtain closed-form relations for different parameters of the structure to achieve the dual-band absorber. Two absorption bands with an obtained absorptivity of 98% at 0.53 and 1.53 THz for the graphene-based structure and 7 and 25 THz for the metallic-based case are achieved. We demonstrate that the graphene-based absorber remains as the dual band for a wide range of the Fermi level. Furthermore, the recommended dual-band absorbers are insensitive in terms of polarization and remain within various incident angles. The most important advantage of this device is its simplicity compared with the previously reported structures. [ABSTRACT FROM AUTHOR]

This paper numerically investigates the relative intensity noise of quantum dot lasers through a rate equation model taking into account both the spontaneous emission and carrier contributions. In particular, results show that the carrier noise originating from the ground and excited states significantly enhances the relative intensity noise of the laser, while that from the carrier reservoir does not. Simulations also point out that a large energy interval between the quantum confined levels is more suitable for low-intensity noise operation due to the reduced contribution from the carrier noise in the excited state. Finally, the carrier noise is found to have little impact on the frequency noise, thus being negligible for the investigation of the spectral linewidth. Overall, this paper is useful for designing low-noise quantum dot oscillators for high-speed communications, optical frequency combs, and radar applications. [ABSTRACT FROM AUTHOR]

This paper proposes a design using a 2-D photonic crystal (PhC) structure-based thin film heterojunction GaAs solar cell with a periodic pattern extending from top transparent conducting oxide to inside the p-AlGaAs window layer placed just above the active layer of GaAs material. This paper presents the theoretical optical study and optimization of all the required parameters. This paper presents the optical optimization study for thin active layer cell in the generalized manner for 50-nm active layer, and then the performance of the proposed structure is compared with Lambertian limits and the planar cell, taken as reference. It has been predicted that these wavelength scale periodic structures greatly enhances the performance of the cell. The improvement in the performance is basically accounted for the better diffraction capability, impedance matching, trapping of high wavelength photons, and reduction in reflections from the top due to the PhC structure. The parameters have been optimized and calculated by means of rigorous coupled wave analysis. [ABSTRACT FROM AUTHOR]

Several groups are currently working on integrated optical resonators. In this context, one of the most interesting implementations is based on high-contrast gratings, featuring high- $Q$ Fano resonances. Mastering these phenomena can potentially open up the possibility to exploit such devices for the implementation of vertical-coupled filters or compact monolithic lasers. To this aim, in this paper, the novel analytic framework introduced in Part I is applied to complement the design guidelines present in the literature. Through explicit expressions of the loop gain eigenvalues, it is possible to predict the positions and quality factors of resonances in crossing and anticrossing points. Moreover, a quantitative connection between these points and Fano resonances is established. The framework presented in this paper has been useful for identifying, in a low-contrast grating, resonance features similar to those well known in high-contrast structures. [ABSTRACT FROM PUBLISHER]

Plasmonic nanolasers are a new class of laser device where surface plasmons are amplified by the stimulated emission in a plasmonic nanocavity. In contrast to conventional lasers, the physical size and the mode volume of plasmonic nanolasers can shrink beyond the optical diffraction limit. The strongly confined optical field leads to high performance of plasmonic nanolasers including ultrafast modulation speed and ultralow power consumption, while on another hand introduces challenges in characterizing their basic lasing properties. In this paper, we systematically characterize the lasing properties of plasmonic nanolasers in spatial, momentum, and frequency spaces simultaneously via leakage radiation microscopy and demonstrate a method to identify the exact lasing modes in a multimode plasmonic nanolaser. This paper advances the understanding of lasing emission behavior in plasmonic nanolasers and paves the way for intentionally manipulating their emission for various applications of on-chip nanophotonic circuits, nonlinear nanophotonics, sensing, and imaging. [ABSTRACT FROM AUTHOR]

This paper presents data on wafer-fused 1550-nm vertical-cavity surface-emitting lasers (VCSELs) based on the active region and distributed Bragg reflectors (DBRs) grown by molecular beam epitaxy. VCSELs with a tunnel junction aperture diameter of 8 μm show lasing at a threshold current density jth <; 3 kA/cm2, an output optical power of ~4 mW, and a -3 dB bandwidth of approximately 7 GHz at a 10-mA bias current. The devices demonstrate single-mode continuous wave operation with the transverse side-mode suppression ratio (SMSR) varying in the range of 40-45 dB up to roll-over currents. The increase in mirror losses due to the etching of the top DBR makes the output optical power increase to 6 mW and causes the wallplug efficiency value to reach 20%, but SMSR remains in the range of 40-45 dB. This also makes it possible to reduce both the photon lifetime and, as a result, the effect of damping and increase the modulation bandwidth to 9 GHz. The observed open and clear eye diagrams indicate that non-return-to-zero operation is possible at bit rates of up to 30 Gbps without equalization or forward error correction. The high-output optical power and modulation performance pave the way for the dense wavelength division multiplexing application of wafer-fused 1550-nm VCSELs. [ABSTRACT FROM AUTHOR]

This paper reports stimulated Brillouin scattering characterization in a tapered optical fiber using full-vectorial finite element-based numerical methods. Numerical simulations of both optical and acoustic waves’ propagation through a tapered microfiber have been carried out. Acoustic modes over a range of wavenumber for different fiber core radii are obtained and nature of their both dominant and non-dominant displacement vector profiles are studied and discussed. Acoustic mode profiles show confinement of the acoustic wave predominantly at the core cladding interface. In addition, the acoustooptical overlap factors at different fiber radii are also presented. [ABSTRACT FROM PUBLISHER]

In this paper, a graphene-based photoconductive antenna (GPCA) is designed by considering its electronic and electromagnetic modeling. For the electronic modeling, energy balance transport model (EBTM) is utilized, because high DC and laser powers are applied to the GPCA, and moreover, it has sub-micron dimensions. On the other hand, for the electromagnetic modeling, an effective conductivity (non-local model) is developed for a graphene strip (GS)-based waveguide by using a semi-classical model to investigate propagation of TM-polarized surface plasmon polaritons (SPPs) by considering spatial dispersion (SD). Additionally, a per unit length circuit model is proposed to validate the non-local model. Then, the GPCA’s working frequency is selected based on the electromagnetic modeling. In the EBTM, by using hot-carriers theory, saturation of photocurrent and velocity overshoot phenomenon (VOP) with regards to the applied bias are investigated. Then, a time-dependent equivalent circuit is proposed to model the GPCA’s operational principles. This circuit enables us to study screening effects in first picoseconds after excitation, which cause saturation of radiated power with respect to the illuminating laser power. Finally, via a coherent detection, radiated THz spectrum is detected through introducing a transfer function for the GPCA. [ABSTRACT FROM PUBLISHER]

The quantum radar cross section (QRCS) is a measure of how electromagnetically “large” an object appears to a quantum radar. The fundamental mechanism that creates the return response is the interaction between the atomic electric dipole moments and the incoming photon. This paper derives the QRCS equation considering the effect of photon polarization in this interaction, as well as providing a means to study bistatic radar geometries. It is found that under normal circumstances, polarization plays no role in the target response. However, if the target’s atomic dipoles are all aligned in one particular direction, such as if the object is in a strong uniform or slowly varying field, polarization has a significant effect on the response by allowing us to “steer” the location of a null to any observation angle desired. Furthermore, scattering can be suppressed in a very large range of scattering angles (not just one) if the polarization of the object and photon are chosen judiciously. It will be shown that this effect is unique to quantum radar and has no classical counterpart. [ABSTRACT FROM AUTHOR]

In this paper, we extract the fundamental resonant mode of a graphene patch using a variational method. We use 2-D eigenvalue problem obtained from the integral equation governing the surface current on graphene patterns under quasistatic approximation. To compute the eigenvalues, we propose three trial eigenfunctions, which meet the boundary conditions. We investigate the accuracy of these eigenfunctions with comparing to the results obtained by full wave simulations. Finally, we analyze square-lattice arrangements of graphene patches using the most accurate proposed eigenfunction and derive a very accurate surface impedance for it. The proposed surface impedance is much more precise than the surface impedance already reported by Padooru et al. for this structure. [ABSTRACT FROM AUTHOR]

The operation of several optical components, such as high-contrast gratings, is based on the interference between two oscillation modes. Therefore, this paper is devoted to the complete characterization of bimodal Fabry–Pérot interferometers, which can effectively model such two-mode interactions. Thanks to a novel parameterization of the mirror scattering matrices, this paper presents for the first time explicit expressions of the bimodal interferometer response, proving phenomena such as 100% reflection peaks, and predicting their positions. For this reason, this paper, which complements—rather than replaces—the existing numerical techniques, provides a completely new perspective on high-contrast gratings. [ABSTRACT FROM PUBLISHER]

High-speed time-gated Single Photon Avalanche Photodiode (SPAD) allows faster detector response times and low afterpulsing effect. Due to the intrinsic capacitance of the SPAD, a fraction of the gate signal is coupled to the readout node. This is unwanted signal and needs to be suppressed. This paper presents a technique to recover the tiny avalanche signal, compensating the high-speed gate feedthrough. The cancellation is carried out in the same way as in the destructive scheme. However, the interfering signal was generated by combining two similar but out-of-phase sinusoidal signals. The proposed scheme is performed using a Micro Photon Devices (MPD) InGaAS/InP SPAD and a Printed Circuit Board (PCB) circuit that has been implemented for this purpose. Tests and measurements were conducted when applying 59.4 V fixed DC supply and 5 $\text{V}_{pp}~1.72$ GHz sinusoidal gating signal. The detector was cooled to 223.15 K, corresponding to 60.4 V breakdown voltage. Applying attenuated laser pulses at 1550 nm, a quantum efficiency of 16% has been measured. The developed technique allowed to suppress the SPAD capacitive response up to 50 dB. In addition, the scheme has provided a better avalanche signal quality compared to a similar circuit employing a low-pass filter to suppress the gate frequency. [ABSTRACT FROM AUTHOR]

We present a comparison of two interband cascade detectors optimized for long-wavelength infrared region: with equal and matched-absorbers. In matched-absorbers architecture, the first absorber determinates the thickness of the subsequent active layer, in order to meet equal quantum efficiency in all stages (QE condition). The simulations showed that quantum efficiency, for both types of architectures, decreases, while the detectivity versus number of stages increases. Detectors with equal absorbers (no QE condition) allow to build more stages in the cascade being the possible way to improve detectivity. On the other hand, structures with matched-absorbers show more flexibility in detectivity improvement by optimal selection of individual active layers. It is shown that structures assumed in this paper do not fully exploit the potential offered by the matched-absorbers approach. The optimal absorber selection allows to reach two times higher quantum efficiency. Moreover, interband cascade detectors optimized for long-wavelength were compared with intersubband quantum cascade infrared photodetectors and HgCdTe showing potential for room temperature operation. [ABSTRACT FROM AUTHOR]

Integrated photonics has been pursued on a large variety of materials and platforms over more than half a century. In recent decades, silicon has emerged as the preferred optical and substrate material. However, since many optical functionalities cannot be, inherently or conveniently, implemented on silicon-based devices, heterogeneous integration of other materials has been an inevitable constituent of silicon photonics from its inception. This paper reviews recent progress in the heterogeneous integration of dielectrics and compound semiconductors as the core optical material for ultracompact nonlinear integrated photonics, preferably on silicon substrates. Occasionally, important devices on native substrates of the core nonlinear material are also reviewed. The focus is on ultracompact photonic devices and circuits formed on submicron films of lithium niobate (LiNbO3), and the aluminium-gallium-arsenide (AlGaAs) and aluminium-gallium-nitride (AlGaN) families for second-order nonlinear processes, such as second-harmonic generation, and techniques to address phase-matching in them. Integration of second- and third-order nonlinear devices on the same chip appears to be a future trend, thus the related preliminary results are reviewed. A broader introduction to heterogeneously integrated photonics, shortcomings of conventional silicon photonics for application in nonlinear optics, as well as an overview of modeling second-order nonlinear integrated-waveguide devices are also provided for completeness. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the temporal behavior of a bistable vertical cavity surface emitting laser (VCSEL) under the effect of optical feedback coming from vibrating diffusely reflecting surface. We demonstrate that a VCSEL operating in the regime of polarization switchings caused by self-mixing effects can greatly enhance a responsivity of the detection of microvibrations. For small amplitudes of microvibrations (less than $\lambda $ /2, where $\lambda $ is the operating wavelength of the laser), which cause only harmonic (or close to harmonic) oscillations in the laser output outside of the bistability region, the use of polarization switching can increase the responsivity up to 45 times. For the amplitudes larger than $\lambda $ /2, the response of a bistable VCSEL well reproduces a fine temporal structure of the self-mixing signal. A procedure of the data processing in the switching regime for the correct determination of the direction of the displacement and for the reconstruction of the waveform of surface vibrations with a basic resolution of $\lambda $ /2 is also shown. [ABSTRACT FROM AUTHOR]

Catastrophic failure of diode pumps in laser systems exhibiting back-irradiance is a common occurrence yet poorly understood. Prior paper has established boundaries for time-zero failures, but these results cannot be used to deduce safe back-irradiance levels for long-term reliable operation. In this paper, a framework to describe the impact of back-irradiance on the reliability of diode pumps is established. The root-cause of back-irradiance induced failure is identified as thermal in nature. The approach follows conventional reliability methodologies by treating the parameters of back-irradiance as stressors, which accelerate failures. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive theoretical study of the optical and thermal properties of an electrically pumped semiconductor nanolaser (SNL) having an GaN/(InGaN/GaN MQWs)/GaN core shell structure. Numerical results show that the lasing whispering-gallery mode has a threshold gain of 413 cm $^{-1}$. Furthermore, it is shown that when it is operated well-above threshold, the device temperature increases by only 22 K above an ambient temperature of 300 K. These promising results are attributed to the strong mode confinement in the active region and the good thermal properties of the material system of the proposed structure. The results presented in this paper offer guidelines for fabrication of electrically pumped room temperature continuous wave SNL operating in the visible spectral region. [ABSTRACT FROM AUTHOR]

A method to provide bandwidth compressed time-mapped spectrogram analysis based on temporal Talbot effect and temporal magnification is proposed and numerically demonstrated in this paper. The signal under test (SUT) is firstly sampled by a periodic pulse train, then passes through a dispersive medium under the Talbot condition and the spectrogram of the SUT is mapped to the time domain, so-called time-mapped spectrogram (TM-SP). Subsequently, a temporal magnification technique is implemented to stretch the time axis and compress the spectrum bandwidth, so that the effect of detection bandwidth on the frequency resolution is alleviated. Though the TM-SP cannot be acquired in a continuous way, the SUT is analyzed with ultrahigh frame rate in the temporal aperture. Additionally, a method to improve acquisition frame rate is proposed. The proposed bandwidth compressed TM-SP analysis is compared with the dispersion-based Fourier transform, and the related tradeoffs are provided in detail. The bandwidth compressed TM-SP analysis with a frequency resolution of 0.1 GHz, a measurable frequency range of 4.85 GHz, an analysis period of 0.1 ns, and an observation period of 4 ns is achieved by simulation. [ABSTRACT FROM AUTHOR]

In the modern era of artificial intelligence, increasingly sophisticated artificial neural networks (ANNs) are implemented, which pose challenges in terms of execution speed and power consumption. To tackle this problem, recent research on reduced-precision ANNs opened the possibility to exploit analog hardware for neuromorphic acceleration. In this scenario, photonic-electronic engines are emerging as a short-medium term solution to exploit the high speed and inherent parallelism of optics for linear computations needed in ANN, while resorting to electronic circuitry for signal conditioning and memory storage. In this paper we introduce a precision-scalable integrated Photonic-Electronic Multiply-Accumulate Neuron (PEMAN). The proposed device relies on (i) an analog photonic engine to perform reduced-precision multiplications at high speed and low power, and (ii) an electronic front-end for accumulation and application of the nonlinear activation function by means of a nonlinear encoding in the analog-to-digital converter (ADC). The device has been numerically validated through cosimulations to perform multiply-accumulate operations (MAC). Simulations are based on the iSiPP50G SOI process for the photonic engine and a commercial 28 nm CMOS process for the electronic front-end. The PEMAN exhibits a multiplication accuracy of 6.1 ENOB up to 10 GMAC/s, while it can perform computations up to 56 GMAC/s with a reduced accuracy down to 2.1 ENOB. The device can trade off speed and power consumption with resolution, significantly outperforming its analog electronics counterparts both in terms of speed and energy consumption. With respect to other photonic ANNs, the PEMAN has comparable speed and energy consumption with a higher resolution, while outperforming them by a hundredfold in the fan-in, which opens the possibility to accelerate more complex networks. [ABSTRACT FROM AUTHOR]

The active mode-locking technique of quantum cascade lasers is highly affected by the bias current level and the magnitude of the modulated signal because of the spatial hole burning effect. The laser generates a stable pulse train near the threshold current and for a high modulation magnitude. We show in this paper an improvement of these conditions with an integration of a single-layer graphene which works as a saturable absorber. The light-matter interaction in the laser active region is described by the two-level Maxwell-Bloch equations and in graphene layer by the Maxwell-Ampere equation and Maxwell-Bloch equations. These system equations are solved using the Finite-Difference Time-Domain (FDTD) method which has the main advantage of not involving any approximation. The weakly coupled splitting scheme is adopted for the time discretization of Maxwell and Bloch equations. The graphene saturable absorption is modelled by a saturable conductivity in Maxwell-Ampere equation and with the dipole moment and carrier density in Maxwell-Bloch equations. For a QCL structure with a gain recovery time of 50 ps, simulation results show better stability of the mode-locking over a broad range of injection current and for smaller magnitude of the modulated signal. QCL structure with gain recovery time close to 1 ps reveals the generation of two pulses per roundtrip linked to spatial hole burning. The carrier grating strength can be reduced by changing the boundary conditions of the cavity such as with a high reflectivity mirror in front of graphene layer. [ABSTRACT FROM AUTHOR]

Recently, electro-optic integrated photonic elements have attracted considerable interest owing to their widespread application in optical communication and signal processing. The strong electro-optical properties and the complementary metal–oxide semiconductor (CMOS) technology compatibility of silicon–organic hybrid structures makes them promising photonic platforms. This study investigated a novel implementation of a high-speed electrically tuned bandpass optical filter using finite-difference time-domain and eigenmode expansion numerical methods. The proposed device was based on a Fabry–Perot cavity and was realized via an electro-optic organic molecular glass filled slot waveguide with Bragg gratings. Furthermore, the calculation considered the plasma dispersion effect, free-carrier absorption in the silicon component of the slot waveguide for different applied voltages, and doping profiles corresponding to ion implantation. It is shown that the spatial distribution of charge carrier density formed by the surface states accumulation/depletion layers has a significant effect on the optical properties of the slot waveguide. Lithographic distortions in the geometry of the proposed structures during fabrication were also considered. Therefore, this paper presents an optical filter designed for fabrication using CMOS-compatible processes on silicon-on-insulator wafers. The filter produced a 3 nm tunable range for a 10 V bias voltage swing, a 0.3 nm full width at half maximum (FWHM) passband with a center at 1550 nm at zero bias voltage, and a 12.5 nm free spectral range with a 27 dB extinction ratio. The proposed device outperforms many narrow passband analogs in terms of sensitivity (tunability: 0.3 nm/V) and can be applied extensively in the fields of optical communications and photonic spectral signal processing. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate ultra-fast millimeter wave beam steering with settling times below 50 ps. A phased array antenna with two elements is employed to realize beam steering. The phased array feeder is implemented with a recently introduced time delay line that provides, at the same time, an ultra-fast tunability, broadband operation, and continuous tuning. Our implementation is used to perform symbol-by-symbol steering. In our demonstration, the beam direction is switched between two sequentially transmitted symbols toward two receivers placed 30° apart. We show the successful symbol-by-symbol steering for data streams as fast as 10 GBd. The suggested scheme shows that the ultra-fast beam steering is becoming practical and might ultimately enable novel high bit-rate multiple access schemes. [ABSTRACT FROM AUTHOR]

This paper describes continuous millimeter-wave and terahertz (THz)-wave applications, where telecom-based photonics technologies are efficiently employed to enhance their performance. First, 300-GHz-band wireless communications are described toward real-time error-free transmissions at 50 Gbit/s and beyond. Next, a novel approach to increase a phase measurement sensitivity in THz frequency-domain spectroscopy systems is explained, and a similar technique is successfully applied to the visualization of electric-field radiation and propagation. Finally, as a futuristic study, the manipulation of THz waves with a concept of photonic crystals and its possible applications to platforms in THz integrated systems are presented. [ABSTRACT FROM AUTHOR]

Tunable vertical-cavity surface-emitting lasers (VCSELs) are becoming key components in several sensing applications, where single-mode, single polarization light is required. In such devices, high-contrast gratings (HCGs) are very promising mirrors, because of their high reflectivity, strong polarization discrimination, and low-volume occupation. However, their introduction might lead to unexpected increases in the threshold gain, destroying the tuning performance. In this paper, these phenomena are investigated and explained in detail. Although VCSEL modes are computed by means of our full 3-D vectorial code, a Gaussian beam model is used to obtain deeper insight into the HCG reflectivity mechanism in the presence of a finite beam. [ABSTRACT FROM AUTHOR]

This paper describes an analysis of multimode nonlinear operation of a 2-D square lattice photonic crystal (PC) laser considering mode competition. The model is based on the semiclassical approach and coupled-mode theory developed for transverse magnetic laser modes. It is showed that for the PC laser, a single-mode operation is dominant within a wide range of the coupling coefficients. [ABSTRACT FROM PUBLISHER]

This Special Issue is associated with the 10th International Conference on Materials for Advanced Technologies (ICMAT), Symposium C: Semiconductor Photonics held on 23–28 June, 2019 at Marina Bay Sands in Singapore. Organised through the Materials Research Society of Singapore (MRS-S), ICMAT has been held since 2001 and has attracted strong interest amongst the global materials science and engineering research communities. The 10th conference in the ICMAT series attracted over 3,500 delegates with a number of keynote and plenary presentations notably including four Nobel Laureates in Physics and Chemistry. The ICMAT conference consists of a number of topical symposia. Symposium C was organized jointly with Australian MRS and co-chaired by Professors Dao-Hua Zhang (NTU, Singapore), Chennupati Jagadish (ANU, Australia), Stephen J. Sweeney (University of Surrey, UK), Boon S. Ooi (KAUST, Saudi Arabia), Hao Gong (NUS, Singapore) and Weijun Fan (NTU, Singapore). The Symposium focused on recent developments in materials for applications in photonic devices covering systems including III-V and II-VI semiconductors, group IV alloys for silicon compatibility, oxides and perovskites for solar cell and emitter applications, quantum dot based devices and in general a wide variety of organic and inorganic materials spanning applications from the ultra-violet through to the mid-infrared. In total, 20 invited and 53 oral and 19 poster papers were presented over the four days of technical sessions. [ABSTRACT FROM AUTHOR]

In this paper, the amplified spontaneous emission (ASE) intensity of a distributed feedback laser diode (DFB-LD) amplified by a semiconductor optical amplifier (SOA) is calculated, and the signal-to-spontaneous emission ratio (SSER) is investigated assuming a wavelength tunable laser. Based on a formulization appropriate for an active layer under a low excitation, the theoretical limit of the SSER of the SOA is obtained, and the SSER including the ASEs from both the DFB-LD and the SOA is numerically calculated. The side mode suppression ratio (SMSR) taking the spectral distribution into consideration is also calculated by expanding the same method. [ABSTRACT FROM AUTHOR]

When a photonic crystal fiber has more than one core, the switching capacity loss among the cores as of a given power, called critical power, becomes a relevant effect for switching applications. In this paper, we study the critical power obtained when ultrashort pulses are propagated in a nonlinear directional coupler. Here, we consider the specific example of a three-core photonic crystal fiber in two possible arrangements: one-dimensional and triangular array. In each core, the pulses propagate in the anomalous dispersion regime, in which an input pulse in the form of a hyperbolic secant is injected into one of the cores, considering different input peak powers. By relating the group velocity dispersion and the coupling coefficient with the temporal width of the input pulse, we can observe some relations between the fiber parameters and the critical power. In addition, we show that when self-phase modulation is combined with other effects, the critical power can be increased or decreased depending on the combination of these effects. [ABSTRACT FROM AUTHOR]

Silicon photomultipliers (SiPM) are photodetectors that have obtained a growing attention in the last years. They have single photon sensitivity, but also a high dynamic range: the output current signal is proportional to the number of detected photons and it is possible to distinguish up to tens of photon per each light pulse. In Fondazione Bruno Kessler (Trento, Italy) we developed the so called high-density SiPMs, with narrow trenches to isolate the cells (i.e. single-photon avalanche diodes) and with high fill factor. These detectors feature high photon detection efficiency and high dynamic range. Moreover, the reduction of the cell size reduces the correlated noise (i.e. lower crosstalk between cells and lower afterpulsing probability) and it makes the singlecell response faster, increasing the maximum counting rate. These characteristics can be very important in applications like light detection and ranging, spectroscopy, and physics experiments. In this paper, we present the structure of high-density SiPMs and their performance. In particular, the photon detection efficiency, the photon number resolving capabilities, the linearity versus photon flux, and the single-photon time resolution, investigating how these parameters change with the cell pitch. [ABSTRACT FROM AUTHOR]

In this paper, we report, through a comparative analysis of static and dynamic measurements, on the impact of mode hopping on the overall intensity noise dynamics of InGaN edge emitting lasers. Mode clustering usually observed in InGaN lasers enhances the mode competition and then the laser intensity fluctuation. Variations as large as 20 dB have been observed. The coexistence of longitudinal modes induces mode competition and then unstable bimodal lasing. This mode competition is mediated by the temporal fluctuations of spontaneous emission through the nonlinear cross saturation of the optical gain. The subsequent enhancement of the relative intensity noise can be detrimental for applications, where the intensity stability of InGaN lasers is a key parameter. Our experimental observations are supported by a simple rate equation model. We point out the major importance of the different modal gain in the bimodal regime on the overall intensity noise of the laser. [ABSTRACT FROM AUTHOR]

In a self-mixing interferometer based on a diode laser, the measurement of the external reflector displacement $s(t)$ is carried out by looking at the optical-phase signal $\cos 2ks(t)$ , a signal readily detected as an amplitude modulation (AM) of emitted power. In contrast, the other available signal, sin $2ks(t)$ , a frequency modulation (FM) of the emitted field at optical frequency, is never used because difficult to recover. Recently, Contreras et al. used a narrow-band acetylene cell to convert the FM into an amplitude signal, finding it is larger and has a better SNR than the AM. In this paper, we analyze the advantages of the new CFM (converted-FM) signal, calculating both amplitude and SNR, and compare theoretical results to published experimental evidence, finding good agreement. We then present options for realizing the selective filter in different configurations and technology. Finally, we evaluate the improvement offered by CFM in a number of measurements, like sub-wavelength vibrations, digital readout displacement, and diode laser alpha factor. [ABSTRACT FROM PUBLISHER]

Since the initial proposal in 1999 by Noda et al., photonic crystal surface emitting lasers (PCSELs) have shown to achieve large area, coherent lasing with a narrow, single mode beam. Owing to their unique orthogonal electrical/optical cavity scheme, PCSELs have emerged as one of the most promising platforms for high power diode lasers. In this paper, we report the performance trade-offs and challenges in power scaling, modal competition, and charge injection control. To address these challenges, we investigate the electrical and optical performances of PCSELs under high-power operation. Heterostructure designs with electron block layers were incorporated for efficient and balanced electrical charge injection. Symmetry breaking strategy was introduced in the photonic crystal design to engineer the in-plane momentum dependent quality factor (Q(k)) for mode discrimination and single mode operation. The impact of electrode designs was also investigated to achieve large area uniform charge injection. Simulation results of these designs indicate promising solutions and improved performances for large-area high-power and single-mode PCSEL operations. [ABSTRACT FROM AUTHOR]

III-V semiconductor lasers are ubiquitous in modern optoelectronic devices, with applications ranging from telecommunication to general lighting. Among the different kinds of laser cavity designs, whispering-gallery mode (WGM) micro-cavity lasers boast outstanding optical performance due to advantages such as ultra-high Q-factor, compact mode volume, and narrow emission linewidth. Over the past decades, research in III-V WGM micro-cavity lasers has progressed rapidly in various aspects, including the fabrication techniques, emission outcoupling methods, and practical applications. In this paper, a comprehensive review is performed on the advances in these aspects. Although III-V WGM lasers are conventionally fabricated with top-down approaches, recent reports have demonstrated the potential of highly-scalable bottom-up methods in fabricating low-loss WGM lasers. Despite the strong optical confinement in III-V WGM cavities, various techniques have been developed to either outcouple WGM emission into waveguides or direct it into free-space with small beam divergence. Finally, recent developments in different applications of III-V WGM micro-cavity lasers are discussed. Other than serving as integrated photonic components, III-V WGM lasers have also displayed exciting potential in other applications such as label-free sensing and the study of cavity quantum electrodynamics (cQED). [ABSTRACT FROM AUTHOR]

In this paper, we present an experimental study of the metrological stabilization of a solid-state frequency comb for embedded metrology applications. The comb is a passively mode-locked laser diode based on InGaAs/InP Quantum-dash structure emitting optical lines into a 9 nm bandwidth centered at $1.55~\mu \text{m}$ with a repetition rate of 10.09 GHz. The frequency stabilization is achieved by optical injection locking of the comb with an external cavity laser diode referenced onto a metrological frequency standard. One observes the transfer of the spectral purity from the injection laser to the neighbouring modes of the injected one as well as the transfer of stability to the adjacent modes. The measurement of the long term stability highlights a frequency noise with random walk behavior specific of the passive mode locking process. Demonstration of sidebands of the injection laser at the repetition frequency of the comb also makes it possible to propose a transfer mechanism and to consider a complete stabilization of the frequency comb at a metrological stability level. [ABSTRACT FROM AUTHOR]

Measuring optical transmission matrix has enabled image detection through scattering media, however its retrieved resolution is severely limited by the number of measurements. In this paper, we introduce super resolution reconstruction into transmission matrix based imaging scheme, to some extent bypassed this limitation. We demonstrate all detailed information of high-resolution subpixel shifting target are preserved in its corresponding speckle signals. And through phase conjugate reconstruction one can get target's low-resolution projection images with accuracy. The final high-resolution image is achieved by subpixel registration and bilinear interpolation operations. The feasibility of the proposed method is theoretically analyzed and proved by laboratory experiments. [ABSTRACT FROM AUTHOR]

This paper provides theoretical insight on how circular Schottky photodiodes in bulk CMOS can be optimized for certain integrated receiver applications. An optimal photodiode size is analytically demonstrated and the effects of a metal plate reflector are simulated using a transfer-matrix method, both for frontside and backside illumination. Finally, a distributed circuit model is presented, which deviates from the classical lumped model for large photodiodes or sheet resistances. The presented methodologies can also be extended to other types of photodetectors. [ABSTRACT FROM AUTHOR]