All-optical set-reset operation of a bistable semiconductor laserintracavity-coupled to a vertical-cavity surface-emitting laser

We experimentally demonstrate a bistable laser diode (BLD) formed by a vertical-cavity surface-emitting laser (VCSEL) coupled to an in-plane laser (IPL) that includes a saturable absorber section. The device can be switched between its two states (corresponding to either the in-plane laser or the vertical-cavity laser being on) by injection of optical pulses. We also discuss possible applications for this device     

Static and dynamic response of multiple-quantum-wellvoltage-controlled bistable laser diodes

We have simulated the static and dynamic characteristics of voltage-controlled multiple-quantum-well (MQW) bistable laser diodes. To investigate the time response of the saturable absorber under applied electric field, we performed pump-probe measurements with picosecond resolution. The obtained differential transmission signals indicate the reduction of the carrier escape time for the saturable absorber with increasing applied electric field. The field screening effect caused by spatial change of the carrier distribution is an important factor, as is phase space filling due to the photogenerated carriers. On the basis of the time response measurements, we have designed an MQW bistable laser by solving the modified rate equation including the recovery time response of the absorption saturation, A saturable absorption region narrower than 10 μm is suitable for obtaining a low threshold device. To achieve low switching power and high switching speed, it is important to optimize the bias conditions and the MQW structures. We can expect a turn-off time of less than 10 ps, and a repetition rate of over 5 GHz from the calculations     

两段式双稳半导体激光器下跳阈值点的确定

对Ｋｕｚｎｅｔｓｏｖ采用的速率方程加以修正，考虑了俄歇效应的影响，我们流子寿命不再作为常数处理，而写成载流子浓度的函数。由此导出了两段式双稳半导体激光器下跳阈值点载流子浓度所满足的隐函数解析表达式。通过该解析表达式确定出了器件存在双稳的必要条件。进而讨论了俄歇复合系数、吸收区偏置电流和长度等对双稳特性的影响。     

Wavelength Bistability in Two-Section Mode-Locked Quantum-Dot Diode Lasers

We report a two-section mode-locked quantum-dot laser with an emission wavelength that is bistable with respect to applied bias on the saturable absorber region. The two stable lasing wavelengths for this device are about 1173 and 1166 nm with a power contrast ratio of over 30 dB. The largest switchable wavelength range is 7.7 nm. The optical power and pulsewidth (6.5ps) are almost identical in the two lasing modes under optimized conditions. The operation of this laser can be explained by the interplay of the spectral-hole burning and the quantum-confined Stark effect     

Threshold behavior of tunnel-diode bistable triggers for linearly varying input pulses

The threshold behavior of a practical tunnel-diode bistable trigger for trapezoidal and triangular input pulses is analytically studied. The results for a wide range of slopes of pulses are compared under different circuit conditions. It is noted that for slowly varying pulses the minimum overdrive requirement is less (which causes a larger delay) and increases with an increase in the slope.     

Laser mode-locking with saturable absorbers

In this paper we describe a mode-locked laser in terms of traveling pulses of light. We show that the energy absorbed by a saturable absorber is a minimum if the pulselength is a minimum, and that two pulses are essentially as favorable as one if they meet at the position of the dye cell. Under steady-state pulsing conditions, however, we show that the pulses will have a width which depends on their energy. We find that for parameters appropriate to present Nd: glass experiments, the expected length is about 10^-11seconds, in agreement with observations. Finally, we demonstrate the rather surprising result that a linearly dispersive medium does not broaden the mode-locked laser pulses to first order.     

InGaAsP/InP CCTS双稳态激光器的纵模及偏振特性

本文给出了InGaAsP/InP CCTS双稳态激光器的模式特性。通过实验得到对双稳态激光器来说其吸收区的存在,使其对偏振及纵模的选择有一定的作用,使得TM模的输出强度在总输出中占的比例更小,及在双稳区内给出单纵模输出。     

Calculation of the colliding pulse mode locking in CW dye ring lasers

A calculation of the influence of a transient absorber grating on the pulse parameters of a dye laser in the "colliding pulse mode-locking" (CPM) regime is given. It is shown that, compared to other passive methods, considerably shorter pulses with a more favorable stability region can be obtained. Within the stability range of single pulse operation the shortest pulses in the CPM are obtained by operating far above threshold where the saturation energy of the amplifier is much greater than that of the absorber. Deviation from an amplifier position that is symmetric with respect to the amplification of the counter-running pulses leads to different energies of the pulses and to a strong decrease of the stability range. Taking the dispersive properties of absorber and amplifier into consideration, equations for the time dependent phase of the laser pulse are established and solved by an analytical ansatz. The resulting pulse chirp is shown to be mainly dependent on the detuning of the pulse frequency from the center frequency of the saturable absorber. The estimated values for the pulse duration and the down-chirp for typical experimental conditions of a rhodamine 6G-DODCI CPM laser agree well with the measured ones.     

Optical regenerative oscillation and monostable pulse generation in electrooptic bistable devices

Optical regenerative oscillation is discussed theoretically and experimentally in three types of mirrorless bistable optical devices based on the electrooptic light modulator. The devices have two feedback signals proportional to the optical output power, and the oscillation condition and oscillation frequency depend on the time constants and conversion factors for two feedback voltages and biasing phase retardation in the light modulator. Analysis is done by treating the coupled differential equations for the time dependent feedback signals. The experimental results agree with the theoretical prediction. We show also that optical monostable pulses can be generated in the three types of bistable optical devices.     

Femtosecond Cr:forsterite laser with mode locking initiated by aquantum-well saturable absorber

We studied a mode-locked Cr:forsterite laser pumped by a diode pumped Nd:YVO₄ laser. Both the Kerr lens mode locking and the semiconductor saturable absorber initiated mode locking have been demonstrated. Using our measured dispersion data of the forsterite crystal, together with our dispersion compensation technique, we obtained 20-fs pulses for the pure Kerr lens mode locking and 36-fs pulses for semiconductor saturable absorber initiated mode locking, respectively     

双区共腔双稳态激光器电注入下特性的计算机模拟

本文对双区共腔半导体双稳态激光器在电注入下的稳态及瞬态特性进行了计算机模拟,这种模型产生双稳和自脉动现象的机制是不均匀电注入本征可饱和吸收特性,我们研究了与可饱和吸收有关的几个参数r、ξ、J_1、J_2对双稳及自脉动现象的影响.     

Erbium-ytterbium waveguide laser mode-locked with a semiconductorsaturable absorber mirror

Picosecond pulses are produced using a semiconductor saturable absorber mirror in a laser based on an Er-Yb codoped planar waveguide amplifier. Continuous-wave mode-locking (CWML) with 9.8-ps pulses is obtained at repetition rates up to 100 MHz. With intracavity spectral filtering, saturable pulsewidths of 1 ps are achieved, and tunable picosecond pulses are obtained from 1534 to 1553 nm. Absorber characterization suggests that two-photon absorption within the saturable absorber mirror influences the CWML stability     

Relaxation Oscillations and Pulse Stability in Harmonically Mode-Locked Semiconductor Lasers

In this paper, we discuss pulse dynamics in harmonically mode-locked semiconductor lasers and present the conditions necessary for stability. In a laser mode-locked at the Nth harmonic, the pulse energy fluctuations have (N+1) different modes of relaxation oscillations. Different modes correspond to different patterns for the energy fluctuations in the N different pulses inside the laser cavity. In the higher order relaxation oscillation modes, the energy fluctuations are negatively correlated in different pulses inside the laser cavity, and these modes can cause instability. Gain saturation on time scales of the order of the pulse width (dynamic gain saturation) stabilizes pulse energy fluctuations with respect to relaxation oscillations. The precise limits on the stable operating regime depend on the gain dynamics at both slow and fast time scales. We also discuss harmonic mode-locking in the presence of a slow saturable absorber. Dynamic loss saturation in a saturable absorber can work against dynamic gain saturation and limit the stability range for harmonic mode-locking.     

Soliton Thulium-Doped Fiber Laser With Carbon Nanotube Saturable Absorber

We report stabilization of a thulium-holmium codoped fiber soliton laser with a saturable absorber based on carbon nanotubes. The laser generates transform-limited 750-fs pulses with 0.5-nJ energy.     

Mode-locking at very high repetition rates more than terahertz inpassively mode-locked distributed-Bragg-reflector laser diodes

We propose a technique for achieving mode-locking at very high repetition rates more than terahertz with high output power using a distributed-Bragg-reflector (DBR) laser, including an intracavity saturable absorber. This method is based on harmonic passive mode-locking at high gain levels and the selectivity of harmonic numbers related to the spectrum-filtering property of the intracavity Bragg reflector. Transform-limited pulses at repetition rates from 500 GHz to 1.54 THz were generated with an output power exceeding 15 mW. We studied stability of harmonic pulses by using conventional self-consistent mode-locking equations. We also discuss the effect of the spectrum-filtering properties of the intracavity Bragg reflector to the characteristics of mode-locked pulses     

New two-mode bistability in an asymmetric absorptive multisectionlaser diode: theoretical analysis

A novel two-mode bistable laser diode (TMBLD) with an asymmetric cavity configuration is proposed and analyzed. It consists of a gain region, a saturable absorber region, and a set of mode-selective mirrors (or filters). These elements are arranged such that the saturable absorber acts as an intracavity loss for one mode and a bleachable absorber external to the cavity of the other mode. Both modes share the same gain medium and compete for the same gain. Bleaching of the absorber leads to a switching of the modes and possible bistability. This two-mode bistability results from the complementary processes of mode competition in the gain section and the mode-dependent effective cross section of the saturable absorber. A rate equation analysis of the device indicates that a switching time less than 200 ps and a modulation rate over 3 Gb/s should be obtainable     

Self-pulsation in multielectrode distributed feedback lasers

Measurements on multielectrode distributed feedback (DFB) lasers without a saturable absorber reveal the existence of a self-pulsation (SP) regime. In this regime, the laser remains in the same single-longitudinal mode with simultaneous intensity and frequency modulation. The laser spectrum is similar to that of a current-modulated single-mode laser. At the up-limit of the SP regime, the behavior between the output power and the injection current becomes bistable. In one branch of the bistable loop, the SP laser presents a very large spectrum without distinguishable peaks, a kind of chaotic state with coherence collapse. A qualitative explanation based on the effective differential gain is given for the origin of SP and associated phenomena in these lasers     

被动调Q激光脉冲周期的研究

针对存在激发态吸收(ESA)的被动式调Q激光器,采用绝热近似(AEA)方法和微分方程的Hopf分岔条件,将被动调Q产生的多脉冲序列与由光强和反转粒子数密度所构成相平面上的极限环运动对应起来,得到了产生Q脉冲阈值的定量关系式和表示脉冲周期(重复频率)的解析解。解释了Cr4+:YAG调Q激光器的有关现象,获得了与有关实验相一致的结果。