IEEE Journal of Quantum Electronics

Numerical Study of Dual Mode Generation Using a Sampled-Grating High-Order Quantum-Dot Based Laterally-Coupled DFB Laser

We propose a fabrication-friendly dual-mode laser source based on a sampled surface-grating, quantum-dot (QD), third-order, and laterally-coupled distributed feedback (LC-DFB) laser composed of alternating grating and Fabry-Perot sections. The dynamic behavior of this device is investigated through numerical modelling, and mode spacing in the millimeter-wave domain (60 GHz) was achieved. We extended a time-domain travelling-wave algorithm, including Streifer's terms, to numerically study the dynamic behavior of the modified high-order LC-DFB lasers. We also incorporated an active QD region via a set of rate equations that considers both in homogeneous broadening because of spatial distribution of QD and homogeneous broadening because of the scattering or polarization dephasing rate. It was found that stable dual mode operation in the millimeter-wave range can be achieved with a dual-side-mode-suppression-ratio as high as
${sim}{rm 50}~{rm dB}$ .

Terahertz Radiation Generated by Laser Induced Plasma in Photoconductive Antenna

To theoretically analyze the spectral characteristics of terahertz (THz) electromagnetic radiation generated by photoconductive antennas, the paper proposed a model by considering laser induced plasma in photoconductive antenna. At a bias voltage, plasma oscillation generates Langmuir wave that propagates in the inhomogeneous plasma in the direction of density gradient, and is converted to THz radiation after a converse zone. The influence factors of the bandwidth and peak frequency are analyzed by the model and testified by experiment.

Low-Frequency Fluctuations in Semiconductor Ring Lasers With Optical Feedback

In this paper, we experimentally and numerically study the dynamics of semiconductor ring lasers that are subjected to long delay and moderate self-feedback. Through varying the pump current or the feedback strength or both, we study the appearance and parameter dependence of low frequency fluctuations in these systems. In particular, we observe different routes to the building up of the initial power amplitude.

Analysis of CW Oxygen-Iodine Laser Performance Using Similarity Criteria

A simplified single-frequency two-level model for predicting power extraction from a CW oxygen-iodine laser (OIL) considering relaxation losses has been developed. The model predicts that the energy efficiency of CW OILs with stable resonators depends on three similarity criteria. Criterion
$gamma_{rm d}$ is the ratio of the residence time of active medium in the resonator to the singlet oxygen
${rm O}_{2}(^{1}triangle)$ energy extraction time at an infinite intraresonator intensity. Criterion
$Pi$ is small-signal gain to the threshold ratio. Criterion
$Lambda$ is the relaxation to excitation rate ratio for the electronically excited iodine atoms
${rm I}(^{2}{rm P}_{1/2})$.

Polarization-Dependent Third-Order Optical Nonlinearity of ${rm BaAlBO}_{3}{rm F}_{2}$ Crystal

We investigated the third-order optical nonlinearity of a new nonlinear optical crystal
${rm BaAlBO}_{3}{rm F}_{2}$ (BABF) using Z-scan technique with a picosecond 532-nm laser. Polarization-dependent nonlinear refractive index
$gamma$ of the BABF crystal was measured with an a-cut sample and a sample cut along the type I phase-matching angle for third-harmonic-generation of lasers at 1064 nm (THG-cut). Anisotropy was observed with positive
$gamma$ values in the range of
$10^{-16}~{rm cm}^{2}/{rm W}$, indicating self-focusing Kerr effects. The measurements agreed well with the theoretical prediction. The corresponding third-order nonlinear optical susceptibility
$chi_{eff}^{(3)}$ was estimated to be
${sim} 10^{-14}~{rm esu}$.

Optically Pumped Semiconductor Lasers for Precision Spectroscopic Applications

Optically pumped semiconductor lasers in conjunction with intra-cavity frequency conversion and tuning elements offer high continuous-wave power, narrow linewidth, and broad tunability. As a result, they are well suited to precision spectroscopic applications. We describe the development and testing of optically pumped semiconductor lasers operating at fundamental wavelengths of 1119 and 1178 nm. The fourth and second harmonic wavelengths are resonant with transitions in Mg II and Na I, respectively. We demonstrate continuously tunable, single-frequency lasers with watt-level average power at 1119, 1178, and 589 nm.

High Power $({>}{rm 10}~{rm W})$ Gold Vapor Laser With Second and Third Harmonics for Telecommunication and Engineering Applications

We report the results from a new class of gold vapor laser that produces 10 W of polarized high beam quality radiation at 627.8 nm with a pulse repetition frequency of 50 kHz. A highly robust laser tube is built from standard non-toxic refractory materials such as a boron nitride plasma tube. For the first time, the kinetic enhancement by the addition of hydrogen and hydrogen chloride to the laser buffer gas is demonstrated for a gold vapor laser. The frequency doubling and tripling of the fundamental beam yield 1.7 W of output at 313.9 nm and 35.5 mW of output at 209.2 nm, respectively. The frequency doubled output of the laser is used to demonstrate polymer micromachining, optical fiber-Bragg grating writing, and through-jacket long-period grating writing in photosensitive optical fiber.

Compact Split Disk Laser With SiC Wafer and Bonding via Liquid Capillarity

The design of split disk laser is proposed and demonstrated with SiC wafer and uncoated
${rm Nd}{:}{rm YVO}_{4}$ disk bonding via liquid capillarity. Using the SiC wafer as an intra-cavity heat spreader, the thermal effects and thermal induced distortions are greatly relieved. Depending on the excellent thermal and optical properties of SiC, a high slope efficiency of 43.3% and 5.3 W CW output power is demonstrated at room temperature without active cooling. No delamination of split disks occurred under lasing conditions. The measured temperature difference agreed with the numerical simulations.

Analysis and Comparison of Single Crystal and Polycrystalline Nd:YAG, Absorption

The optical properties of polycrystalline and single crystal Nd:YAG materials are reported. Materials include undoped, 1%, 1.5%, 2%, 4%, 6%, and 10% at. Nd doped polycrystalline YAG and undoped and 1% at. Nd doped single crystal YAG. The motivation of this paper is to determine the ideal material type and doping percentage gain media for use in a high energy 0.946
$mu{rm m}$ Nd:YAG laser. Room temperature transmittance measurements for all samples are performed between the midinfrared and ultraviolet edges of absorption. From this calibrated transmittance data, an extinction coefficient and extinction cross section are calculated across the entire spectra. We determine that, for the doping percentages measured, the extinction cross section is independent of doping level. Our measured extinction cross sections are consistent with previously reported values. Temperature dependent transmittance measurements are conducted on 1% and 6% polycrystalline Nd:YAG material. A classical oscillator model for the diode pump band absorption coefficient is presented.

Spatial Gain Overlap-Controlled Hysteresis in Multimode Interference-Based Bistable Laser Diodes

Multimode interferometer bistable laser diodes (MMI-BLDs) appeared recently as a potential candidate for implementing all-optical flip-flops. It was reported that in such MMI-BLDs, cross-gain saturation effect and saturable absorber together can control the hysteresis window characteristics; however, there was no clear description on how to analyze and estimate the effect of cross-gain saturation on hysteresis characteristics. In this paper, we present a model that can explain the experimental results reported for MMI-BLDs and predict the hysteresis behavior for such devices. The proposed simulation model can work for both symmetric and asymmetric configurations of MMI-BLDs as it considers the spatial gain overlap between the co-propagating modes inside the MMI-BLDs. This spatial overlap accounts for the discrepancies in hysteresis characteristics, i.e., hysteresis width and threshold currents, between both configurations. With the proposed model, as the asymmetric configuration provides variable spatial cross-gain overlap between the fundamental and first-order modes depending on device dimensions, hysteresis window characteristics vary accordingly.

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