Quantum efficiency enhancement of reflective GaAs photocathodes with exponential-doping structure generating a favorable built-in electric field.

The rapid development of GaAs photocathodes has led to an increased focus on the attainment of high quantum efficiency. Three types of exponential-doping structures with a high to low doping concentration distribution from the interior to the surface are proposed for reflective GaAs emission layers. These three structures generate different built-in electric fields that facilitate photoelectron emission.

Impact of the Interruption Duration on Photoluminescence Properties of MOCVD-Grown GaAsP/InAlGaAs Quantum Well Structures.

The growth interruption technology is introduced to the growth of GaAsP/InAlGaAs quantum well (QW) structure using metal-organic chemical vapor deposition (MOCVD). The effect of growth interruption time (GIT) on the crystalline quality and optical properties are investigated. The two distinctive emission peaks are the transition recombination between the electron level of conduction band and the light and heavy hole level of valence band in the photoluminescence (PL) at room temperature.

Adjoint Algorithm Design of Selective Mode Reflecting Metastructure for BAL Applications.

Broad-area lasers (BALs) have found applications in a variety of crucial fields on account of their high output power and high energy transfer efficiency. However, they suffer from poor spatial beam quality due to multi-mode behavior along the waveguide transverse direction. In this paper, we propose a novel metasurface waveguide structure acting as a transverse mode selective back-reflector for BALs.

A Design of High-Efficiency: Vertical Accumulation Modulators Based on Silicon Photonics.

On-chip optical modulators, which are capable of converting electrical signals into optical signals, constitute the foundational components of photonic devices. Photonics modulators exhibiting high modulation efficiency and low insertion loss are highly sought after in numerous critical applications, such as optical phase steering, optical coherent imaging, and optical computing. This paper introduces a novel accumulation-type vertical modulator structure based on a silicon photonics platform.

From coarse to fine: Two-stage deep residual attention generative adversarial network for repair of iris textures obscured by eyelids and eyelashes.

We propose a two-stage deep residual attention generative adversarial network (TSDRA-GAN) for inpainting iris textures obscured by eyelids. This two-stage generation approach ensures that the semantic and texture information of the generated images is preserved. In the second stage of the fine network, a modified residual block (MRB) is used to further extract features and mitigate the performance degradation caused by the deepening of the network, thus following the concept of using a residual structure as a component of the encoder.

Wavelength tuning robustness optimization for a high-temperature single-mode VCSEL used in chip-scale atomic sensing systems.

In this paper, the wavelength current tuning characteristics of high-temperature-operation single-mode vertical-cavity surface-emitting lasers (VCSELs) for chip-scale atomic sensing systems are studied. Excellent wavelength current tuning robustness is helpful to improve the stability of atomic sensing systems. By optimizing the size of the oxide aperture combined with surface relief mode control technology, the single-mode VCSEL with an 8 µm oxide aperture can achieve 2.

Simulation and experimental research of a high-order Bragg grating semiconductor laser.

In this paper, the influence of the epitaxial structure on distributed Bragg reflector (DBR) grating characteristics is studied by simulation analysis. Comparative analysis shows that the symmetrical epitaxial structure can achieve a lower threshold current and, thus, a higher power. Based on the simulated structure, a DBR laser based on a symmetric epitaxial structure was fabricated, and a single longitudinal mode laser output at ∼1060 was obtained.

High-power vertical external-cavity surface-emitting laser emitting switchable wavelengths.

In this paper we reported on the optically pumped VECSELs with switchable lasing wavelengths. The two lasing wavelengths of λ ≈ 954 nm and 1003 nm are generated at different pumping powers from the same gain chip. The thermal rollover of output power is observed twice, and the first rollover on the power curve indicates the switch of lasing wavelength.

High-order DBR semiconductor lasers: effect of grating parameters on grating performance: publisher's note.

This publisher's note amends the author listing in Appl. Opt.59, 8789 (2020)APOPAI0003-693510.

High-order DBR semiconductor lasers: effect of grating parameters on grating performance.

In this paper, a high-order distributed Bragg reflector (DBR) semiconductor laser operating at 1064 nm is demonstrated based on simulation analysis. To get optimal Bragg grating characteristics, four parameters of the Bragg grating were analyzed in detail. Forty-nine-order Bragg gratings were designed with a reflectivity of 6% and a FWHM of 3 nm, which can realize mode selection while lasing.

Carrier Dynamic Investigations of AlGaInAs Quantum Well Revealed by Temperature-Dependent Time-Resolved Photoluminescence.

AlGaInAs quantum well (QW) lasers have great potential in the application fields of optical communications and eye-safety lidars, owing to the advantages of good gain performance. A large amount of experimental evidence indicated that carrier dynamic affects the resonant frequency and modulation response performance of QW lasers. However, the mechanism of carrier dynamic in AlGaInAs QW structure is still ambiguous for complicated artificial multilayers.

Microscopic View of Defect Evolution in Thermal Treated AlGaInAs Quantum Well Revealed by Spatially Resolved Cathodoluminescence.

An aluminum gallium indium arsenic (AlGaInAs) material system is indispensable as the active layer of diode lasers emitting at 1310 or 1550 nm, which are used in optical fiber communications. However, the course of the high-temperature instability of a quantum well structure, which is closely related to the diffusion of indium atoms, is still not clear due to the system’s complexity. The diffusion process of indium atoms was simulated by thermal treatment, and the changes in the optical and structural properties of an AlGaInAs quantum well are investigated in this paper.

High-power dual-wavelength lasing in bimodal-sized InGaAs/GaAs quantum dots.

In this paper, we demonstrate high power, dual-wavelength (dual-λ) lasing stemming from bimodal-sized InGaAs/GaAs quantum dots (QDs). The device exhibits simultaneous dual-λ lasing at 1015.2 nm and 1023.

Bimodal-sized quantum dots for broad spectral bandwidth emitter.

In this work, a high-power and broadband superluminescent diode (SLD) is achieved utilizing bimodal-sized quantum dots (QDs) as active materials. The device exhibits a 3 dB bandwidth of 178.8 nm with output power of 1.

Effect of Cs adsorption on the photoemission performance of GaAlAs photocathode.

The effect of Cs adsorption on the photoemission performance of a reflection-mode GaAlAs photocathode in an ultrahigh vacuum chamber has been investigated. The experiments for Cs/O activation, multiple recaesiation, and degradation are performed on a GaAlAs photocathode. Meanwhile, the Cs/O activated and recaesiated photocurrent curves, degraded photocurrent curves, and spectral response curves are measured and analyzed.

Design and comparison of GaAs, GaAsP and InGaAlAs quantum-well active regions for 808-nm VCSELs.

Vertical-cavity surface-emitting lasers emitting at 808 nm with unstrained GaAs/Al0.3Ga0.7As, tensilely strained GaAs(x)P(1-x)/Al0.