Search Results (120)

In this study, a simulation-based investigation of the variations of the bit error rate (BER) and the maximum quality factor are presented for short- (S-), conventional- (C-), and long- (L-) band wavelengths in a photonic ultra-wideband (UWB) circuit using a semiconductor optical amplifier (SOA) with different bias currents and a bandpass filter (BPF). Gaussian quadruplet UWB pulses are generated at the S-, C-, and L-band wavelengths, which are commonly used in fiber transmission lines. An analysis of the temporal and spectral features of the generated pulses is carried out. The highest maximum quality factor and the lowest minimum BER are obtained in the C-band at an SOA bias current of 150 mA. This study simultaneously investigates both UWB pulse generation and transmission performance. The proposed circuit has a simple design and high applicability, as it employs a SOA, a Gaussian optical filter, a low-pass filter (LPF) and a single BPF. Full article

Increasing data rates in optical networks require ultra-fast all-optical logic gates to avoid electro-optic conversion bottlenecks. This work presents a numerical simulation and performance analysis of an all-optical XNOR logic gate operating at 250 Gb/s, implemented using a single quantum-dot semiconductor optical amplifier (QD-SOA) embedded in a Mach–Zehnder interferometer (MZI). Using the QD-SOA’s ultrafast carrier dynamics and high nonlinearity, the gate achieves a quality factor (QF) of 26.30 at 250 Gb/s, corresponding to a theoretical bit-error rate below 10⁻⁹. A systematic numerical investigation examines performance dependence on six critical parameters. Data rate analysis shows that the gate maintains QF > 6 up to 700 Gb/s, with QF = 10.47 at this maximum reliable speed, providing a safety margin of approximately 1.8× above the QF = 6 threshold. Performance degrades progressively thereafter, with QF falling to 5.18 at 800 Gb/s and 0.73 at 1 Tb/s due to finite carrier recovery dynamics. Pulse energy optimization identifies an optimum at 0.20 pJ, beyond which gain saturation and nonlinear effects degrade performance below QF = 6 at 0.40 pJ. Continuous-wave probe power exhibits optimal operation at 0.40 mW, with failure above 0.80 mW. Injection current density analysis establishes an optimal bias at 4 kA/cm², where balanced gain and nonlinearity yield peak performance. Noise tolerance assessment demonstrates operation up to a spontaneous emission factor of 6 and phase noise below 6 × 10⁻¹⁴ rad²/Hz, beyond which signal integrity collapses. This parameter sweep delineates the operational envelope and optimization guidelines for QD-SOA-MZI-based all-optical logic, confirming its potential as a compact core component for future ultra-high-speed optical communication and signal processing systems. Full article

This study proposes a 300 W class Gallium Nitride (GaN) Solid-State Power Amplifier (SSPA)-based microwave plasma generator system for implementing next-generation light sources with high brightness and color rendering at 2.45 GHz. To overcome the lifetime limitations and control constraints of conventional magnetron systems, the proposed system introduces custom packaging technology utilizing GaN-on-SiC Bare-dies fabricated via the Win-semiconductor’s NP25 process. This approach minimizes parasitic components and significantly reduces thermal resistance compared to standard packages, ensuring reliability during high-power operation. A stable RF output of 300 W was achieved through two-stage power combining. For the plasma source, an Ar-InBr-Hg gas mixture was employed to optimize optical characteristics. This gas mixture is commonly used in electrodeless plasma lamps due to its high luminous efficacy and stable discharge characteristics. To analyze the rapid impedance discontinuity during gas ignition, numerical analysis based on the Drude model was performed, theoretically identifying the complex permittivity transition of the medium and the resulting resonant frequency up-shift mechanism. To mitigate system instability during this transition, an adaptive frequency tracking and feedback control loop based on real-time VSWR monitoring was implemented. Experimental results demonstrate precise tracking within a 100 MHz frequency variable range, achieving a system efficiency of over 53% and maintaining a VSWR below 1.15:1. These results validate the practical feasibility of GaN SSPA technology in electrodeless lighting and industrial plasma applications utilizing high-power RF energy. Full article

We demonstrate a monolithically integrated photonic chip that combines an optical spiking neuron with a tunable synaptic element. The spiking neuron is realized using a quantum-well Fabry–Perot laser integrated with a saturable absorber (FP-SA), while a semiconductor optical amplifier (SOA) functions as a photonic synapse. Two photonic-crystal (PC) mirrors define the laser cavity and enable effective modulation of the synaptic weight. Experimental results further confirm the capability of the SOA for continuous and controllable synaptic weight tuning. This work represents an important step toward scalable on-chip photonic spiking neural networks. Full article

Semiconductor optical amplifiers (SOAs) are central to the development of ultrafast, low-power all-optical signal processing systems. Their strong nonlinear response, compact size, and compatibility with photonic integration platforms make them key enablers for implementing all-optical logic functions beyond the limitations of electronic switching. This review offers a comprehensive analysis of the principal SOA technologies used in all-optical logic gate implementations, including conventional bulk and quantum well SOAs, quantum dot SOAs (QD-SOAs), photonic crystal SOAs (PhC-SOAs), reflective SOAs (RSOAs), and carrier reservoir SOAs (CR-SOAs). For each architecture, we examine the carrier dynamics, gain recovery mechanisms, saturation behavior, and fabrication considerations, together with their associated nonlinear effects such as cross-gain modulation, cross-phase modulation, and four-wave mixing. We further evaluate reported implementations of key logic operations—AND, NAND, OR, NOR, XOR, and XNOR—highlighting performance trade-offs in terms of speed, extinction ratio, operational power, integration complexity, and scalability. The review concludes with current challenges and emerging research directions aimed at realizing fully integrated, high-speed, and energy-efficient all-optical logic systems based on next-generation SOA technologies. Full article

The sustained interest in efficient, low-cost, and straightforward-to-manufacture lasers has prompted intense research into organic semiconductor laser emitter materials in recent decades. The main focus of this research is determining the optical gains and losses of amplified spontaneous emission (ASE) in order to describe materials by their amplification signature. A method that has been used for decades as the standard technique for determining gain characteristics is the variable-stripe-length (VSL) method. The success of the VSL method has led to the development of further measurement techniques. These techniques provide a detailed insight into the nature of optical amplification. One such method is the scattered emission profile (SEP) method. In this study, we present an extension of the SEP method, the Diffracted Emission Profile (DEP) method. The DEP method is based on the detection of ASE by partial decoupling of waveguide modes diffracted by a one-dimensional grating integrated into a planar waveguide. Diffraction causes a proportion of the intensity to exit the waveguide, transferring the growth and decay process of the waveguide mode to the transverse mode profile of the diffracted mode. In the present article, an approach to determine the amplification signature of an organic copolymer is presented, utilizing partial decoupled radiation. Full article

The dissipative Kerr soliton (DKS) microcomb has been regarded as a highly promising multi-wavelength laser source for optical fiber communication, due to its excellent frequency and phase stability. However, in some specific application scenarios, such as direct modulation and direct detection (DM/DD), the relative intensity noise (RIN) performance of Kerr optical combs still fails to meet the requirements. Here, we systematically investigate the key factors that contribute to the power fluctuations in DKS combs. By exploiting the gain saturation effect of the semiconductor optical amplifier (SOA), the RIN of an on-chip DKS microcomb is effectively suppressed, achieving a maximum reduction of about 30 dB (@600 kHz offset frequency) for all comb lines. Moreover, such DKS comb RIN suppression technology based on an SOA chip can eliminate the need for additional complex feedback control circuits, showcasing the potential for further chip integration of the ultra-low-RIN DKS microcomb system. Full article

As optical networks continue to evolve toward higher speed and larger capacity, conventional security mechanisms relying on optoelectronic conversion are facing increasing limitations. The optical photonic firewall, as an emerging optical-layer security device, enables direct inspection in the optical domain, making its core technology—All-Optical Pattern Matching (AOPM)—a focal point of current research. This review provides a comprehensive survey of AOPM systems. It first introduces the main components of AOPM, namely symbol matching and system architectures, and analyzes their representative implementations. For low-order modulation formats such as OOK and BPSK, the review highlights matching schemes enabled by semiconductor optical amplifier (SOA) and highly nonlinear fiber (HNLF) logic gates, as well as their potential for reconfigurable extension. Building upon this foundation, the paper focuses on systems for high-order modulation formats including QPSK, 8PSK, and 16QAM, covering dimensionality-reduction-based approaches (e.g., PSA-based phase compression, squarer-based phase multiplication, constellation-mapping-based format conversion), direct symbol matching methods (e.g., phase interference, generalized XNOR, real-time Fourier transform correlation), and reconfigurable designs for multi-format adaptability. Furthermore, the review discusses optimization challenges under non-ideal conditions, such as noise accumulation, phase misalignment, and phase-locking-free operation. Finally, it outlines future directions in robust high-order modulation handling, photonic integration, and AI-driven intelligent matching, offering guidance for the development of optical-layer security technologies. Full article

We study the optical susceptibility of a CdSe-based semiconductor quantum dot with a cascade exciton–biexciton configuration, which is coupled via the Coulomb interaction to a gold spheroidal nanoparticle, in the presence of a nearly resonant strong pump field and a weak probe field. We take both fields’ polarization vectors to be parallel to the interparticle axis, derive the equations of motion for the density matrix, and proceed with a perturbative expansion approach to calculate the components of the density matrix associated with the effective optical susceptibility, which describes processes to first order in the probe field and to all orders in the pump field. We present spectra of the effective susceptibility and examine their dependence on the metal nanoparticle’s geometric characteristics for various interparticle distances and pump field detunings, under both one- and two-photon resonance conditions. The role of the biexciton energy shift is also studied. Lastly, we introduce a dressed-state picture to elucidate the origin of the observed spectral features. Our calculations reveal that reducing the interparticle distance and increasing the metal nanoparticle aspect ratio enhance the exciton–plasmon coupling, leading to pronounced resonance splitting, spectral shifts, and broadened gain regions. Prolate nanoparticles aligned with the field polarization exhibit the strongest coupling and the widest gain bandwidth, whereas oblate geometries produce nearly overlapping resonances. Under exact resonance, the probe displays zero absorption with a negative dispersion slope, indicating slow-light behavior. These results demonstrate the tunability of hybrid CdSe-Au nanostructures for designing nanoscale optimal amplifiers, modulators, and sensors. Full article

Perovskite materials have emerged as promising candidates for next-generation photodetectors (PDs) owing to their superior optoelectronic properties and compatibility with low-cost, low-temperature fabrication processes. Broad applicability of PDs spans diverse fields, including X-ray detection, wearable electronics, autonomous vehicles, artificial intelligence, imaging, optical communication, and biomedical sensing, offering advantages over conventional semiconductor PDs based on Si, Ge, InGaAs, and GaN. The integration of plasmonic nanostructures into perovskite-based devices has recently emerged as an effective strategy to enhance performance by amplifying light absorption near the perovskite layer. This review summarizes recent advances and design strategies for plasmonic-integrated perovskite photodetectors (Pe-PDs), with a particular emphasis on plasmonic nanopatterns and nanoparticles as viable approaches for solution-processable Pe-PDs. Full article

Terahertz (THz) frequencies, spanning from 0.1 to 1 THz, are poised to play a pivotal role in the development of future 6G wireless communication systems. These systems aim to utilize photonic technologies to enable ultra-high data rates—on the order of terabits per second—while maintaining low latency and high efficiency. In this work, we present a novel photonic method for generating sub-THz vector signals within the THz band, employing a semiconductor optical amplifier (SOA) and phase modulator (PM) to create an optical frequency comb, combined with in-phase and quadrature (IQ) modulation techniques. We demonstrate, both through simulation and experimental setup, the generation and successful transmission of a 0.1 THz vector. The process involves driving the PM with a 12.5 GHz radio frequency signal to produce the optical comb; then, heterodyne beating in a uni-traveling carrier photodiode (UTC-PD) generates the 0.1 THz radio frequency signal. This signal is transmitted over distances of up to 30 km using single-mode fiber. The resulting 0.1 THz electrical vector signal, modulated with quadrature phase shift keying (QPSK), achieves a bit error ratio (BER) below the hard-decision forward error correction (HD-FEC) threshold of ${3.8 \times 10}^{-3}$. To the best of our knowledge, this is the first experimental demonstration of a 0.1 THz photonic vector THz wave based on an SOA and a simple PM-driven optical frequency comb. Full article

Encryption and decryption are essential components in signal processing and optical communication systems, providing data confidentiality, integrity, and secure high-speed transmission. We present a novel design and simulation of an all-optical encryption and decryption system operating at 120 Gb/s using carrier reservoir semiconductor optical amplifiers (CR-SOAs) embedded in Mach–Zehnder interferometers (MZIs). The architecture relies on two consecutive exclusive-OR (XOR) logic gates, implemented through phase-sensitive interference in the CR-SOA-MZI structure. The first XOR gate performs encryption by combining the input data signal with a secure optical key, while the second gate decrypts the encoded signal using the same key. The fast gain recovery and efficient carrier dynamics of CR-SOAs enable a high-speed, low-latency operation suitable for modern photonic networks. The system is modeled and simulated using Mathematica Wolfram, and the output quality factors of the encrypted and decrypted signals are found to be 28.57 and 14.48, respectively, confirming excellent signal integrity and logic performance. The influence of key operating parameters, including the impact of amplified spontaneous emission noise, on system behavior is also examined. This work highlights the potential of CR-SOA-MZI-based designs for scalable, ultrafast, and energy-efficient all-optical security applications. Full article

In this paper, we present a directly modulated laser (DML) using a partially corrugated grating (PCG) and integrated with a semiconductor optical amplifier (SOA). The influence of the quasi-high-pass filter properties of the SOA on the bandwidth was explored, resulting in high optical power output at lower current levels, with a bandwidth surpassing 25 GHz and an output power above 25 mW. The PCG design boosts the lasing mode’s resistance to random phase fluctuations at the rear facet, hence boosting the mode stability of the laser with a side-mode suppression ratio (SMSR) of over 44 dB. Furthermore, we performed back-to-back (BTB) 26.5625 Gbps NRZ data transmission experiments at room temperature (25 °C) with a modulation current of 60 mA. The results reveal that the transmitter and dispersion eye closure (TDEC) of the fabricated DML is lower than that of a conventional laser when the SOA area current reaches a specific threshold, demonstrating the enhanced signal transmission capabilities of our design. This laser structure offers a fresh strategy for the development of high-power, high-speed DMLs. Full article

All-optical encoders and comparators are essential components for high-speed optical computing, enabling ultra-fast data processing with minimal latency and low power consumption. This paper presents a numerical analysis of an all-optical encoder and comparator architecture operating at 120 Gb/s, based on carrier reservoir semiconductor optical amplifier-assisted Mach–Zehnder interferometers (CR-SOA-MZIs). Building upon our previous work on all-optical arithmetic circuits, this study extends the application of CR-SOA-MZI structures to implement five key logic operations between two input signals (A and B): $\overline{\mathrm{A}}\mathrm{B}$, $\mathrm{A}\overline{\mathrm{B}}$, AB (AND), $\overline{\mathrm{A}}\hspace{0.17em}\overline{\mathrm{B}}$ (NOR), and AB + $\overline{\mathrm{A}}\hspace{0.17em}\overline{\mathrm{B}}$ (XNOR). The performance of these logic gates is evaluated using the quality factor (QF), yielding values of 17.56, 17.04, 19.05, 10.95, and 8.33, respectively. We investigate the impact of critical design parameters on the accuracy and stability of the logic outputs, confirming the feasibility of high-speed operation with robust signal integrity. These results support the viability of CR-SOA-MZI-based configurations for future all-optical logic circuits, offering promising potential for advanced optical computing and next-generation photonic information processing systems. Full article

Lithography is crucial to semiconductor manufacturing, enabling the production of smaller, more powerful electronic devices. This review explores the evolution, principles, and advancements of key lithography techniques, including extreme ultraviolet (EUV) lithography, electron beam lithography (EBL), X-ray lithography (XRL), ion beam lithography (IBL), and nanoimprint lithography (NIL). Each method is analyzed based on its working principles, resolution, resist materials, and applications. EUV lithography, with sub-10 nm resolution, is vital for extending Moore’s Law, leveraging high-NA optics and chemically amplified resists. EBL and IBL enable high-precision maskless patterning for prototyping but suffer from low throughput. XRL, using synchrotron radiation, achieves deep, high-resolution features, while NIL provides a cost-effective, high-throughput method for replicating nanostructures. Alignment marks play a key role in precise layer-to-layer registration, with innovations enhancing accuracy in advanced systems. The mask fabrication process is also examined, highlighting materials like molybdenum silicide for EUV and defect mitigation strategies such as automated inspection and repair. Despite challenges in resolution, defect control, and material innovation, lithography remains indispensable in semiconductor scaling, supporting applications in integrated circuits, photonics, and MEMS/NEMS devices. Various molecular strategies, mechanisms, and molecular dynamic simulations to overcome the fundamental lithographic limits are also highlighted in detail. This review offers insights into lithography’s present and future, aiding researchers in nanoscale manufacturing advancements. Full article