IEEE Journal of Quantum Electronics

A Numerical Study of Cavity Enhanced Inter-Modal Four Wave Mixing in Injection-Locked Semiconductor Ring Lasers

Mode beating via third order nonlinearity in semiconductor ring lasers has been analyzed using a frequency-domain multimode rate equation model. Compared with Fabry–Perot lasers, semiconductor ring lasers are 1.33, 2, and 4 times more efficient in self-gain compression, cross-gain compression, and four-wave mixing processes, respectively, due to its travelling-wave nature. It is shown that, using dual (pump and signal) external optical injections into the ring laser cavity, multiple modes can be locked in phase via the strong four wave mixing phenomenon. This results in modulation of the light wave at the mode beating frequencies which could be used for RF optical carrier generation.

All-Optical Directional Switching in Bistable Semiconductor-Ring Lasers

We investigate the operation of directionally bistable semiconductor-ring lasers as all-optical flip-flops. We demonstrate fast switching between the two lasing directions by injection of optical pulses acting as set and reset control signals with switching times as fast as 20 ps, delay times as short as 60 ps, and switching energy of 150 fJ.

Extremum-Seeking Control of a Mode-Locked Laser

An adaptive controller is demonstrated that is capable of both obtaining and maintaining high-energy, single-pulse states in a mode-locked fiber laser. In particular, a multi-parameter extremum-seeking control (ESC) algorithm is used on a nonlinear polarization rotation (NPR) based laser using waveplate and polarizer angles to achieve optimal passive mode-locking despite large disturbances to the system. The physically realizable objective function introduced divides the energy output by the kurtosis of the pulse spectrum, thus balancing the total energy with the coherence of the mode-locked solution. In addition, its peaks are high-energy mode-locked states that have a safety margin near parameter regimes where mode-locking breaks down or the multipulsing instability occurs. The ESC is demonstrated by numerical simulations of a single-NPR mode-locked laser and is able to track locally maximal mode-locked states despite significant disturbances to parameters such as the fiber birefringence.

Heterodyne Random Bit Generation Using an Optically Injected Semiconductor Laser in Chaos

Heterodyne generation of parallel random bit streams from chaotic emission of an optically injected semiconductor laser is investigated. The continuous-wave optical injection invokes chaotic dynamics in the laser. The broadband chaotic emission is detected through optical heterodyning and electrical heterodyning into different channels. The channels digitize the signals into parallel independent random bit streams. Because of efficient utilization of different portions of the chaos bandwidth, heterodyne detections enable parallel generation of random bit streams, offer high total output bit rates, and require no high-bandwidth analogue-to-digital converters. In the experiment, two optical heterodyne channels and four electrical heterodyne channels are implemented. Each channel is required to digitize only 2.5 GHz of a much broader chaos bandwidth. The sampling rate is 10 GHz with five least significant bits selected from every 8-bit sample. The total output bit rate reaches 100 Gb/s and 200 Gb/s for optical and electrical heterodyning, respectively.

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.

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