1064nm固体激光器和光纤激光器在制备压缩真空态光场实验中的对比研究

实验和理论研究了单频固体激光器和单频光纤激光器的相对强度噪声对压缩真空态光场测量精度的影响.在实验中分别采用单频固体激光器和单频光纤激光器作为实验系统的光源,直接探测到的压缩真空态光场的压缩度分别为(13.2±0.2) dB和(10±0.2) dB.通过理论计算得知本实验中影响可测压缩度的主要因素是光源的相对强度噪声,为实用化的高压缩度压缩真空态光场发生器的研制提供了理论和实验指导.     

面向空间引力波探测的毫赫兹频段低强度噪声单频激光器

低噪声单频激光器是空间引力波探测系统中的核心器件,其噪声性能直接影响空间引力波探测器的灵敏度.本文报道了一种面向空间引力波探测的低噪声单频激光器,利用全保偏光纤结构的功率放大器对低功率、窄线宽、低噪声的非平面环形振荡器输出激光进行放大.为降低激光的强度噪声,比较了不同泵浦源的输出特性,为光纤放大器选用波长锁定的泵浦源,降低泵浦光波长随温度漂移对输出功率的影响,利用光电负反馈控制技术抑制输出激光的强度噪声,结合主动精确控温技术抑制关键器件的热噪声,实现了毫赫兹频段强度噪声的抑制.利用自主搭建的4通道相对强度噪声测量系统,测得反馈控制后的激光器相对强度噪声在1 mHz—1 Hz频段内低于-60 dBc/Hz,在1 mHz和1 Hz处分别为-63.4 dBc/Hz和-105.8 dBc/Hz.研究结果表明,通过放大器泵浦电流的反馈控制和关键器件的温度控制可以有效地抑制激光器在毫赫兹频段的强度噪声,为进一步提高低频段强度噪声性能奠定基础.     

激光自混频干涉效应中相位噪声的测量

本文研究了半导体激光器的自混频干涉效应,使用法布里-珀罗腔将输入场的相位噪声转换为强度噪声,完成了不同反馈以及不同外部距离下相位噪声的测量,并与自由运转时量子阱半导体激光器的相位噪声进行了比较.理论与实验基本一致.     

自由运转半导体激光器边模间的强度关联

半导体激光器的强度和相位起伏一直是影响其应用的关键所在.在实验上研究了自由运转模式下半导体激光器的强度噪声.采用自制的分辨率为0.01 nm的光谱仪成功地分辨出数十个边模，并利用射频低噪声光电探测器系统，分析了激光器的主模与边模之间以及各边模之间的强度噪声关联特性.从实验上证实了主模与边模之间的负关联效应，同时观察到边模之间存在的周期性负关联.该结果对进一步认识半导体激光器噪声的产生机制及强度压缩光的产生机制具有重要意义. 关键词： 半导体激光器 强度噪声 负关联     

法布里-珀罗腔对相位噪声测量的影响

从理论上讨论了通过法布里－珀罗腔将输入场的相位噪声转换为强度噪声的过程。分析了腔参数对输入场相位噪声测量的影响，并对自由运转时单模量子阱激光器相位噪声进行了测量。     

高功率光纤激光器中ASE噪声的测量方法（英文）

高峰值功率脉冲光纤激光器在激光雷达系统中有着广泛的应用。然而,光纤激光器中放大自发辐射噪声(ASE)严重影响了系统的探测性能。提出一种测量高峰值功率脉冲光纤激光器中ASE噪声的方法。在该方法中,首先对高峰值功率的激光脉冲衰减,然后在时域分别测量和计算ASE噪声和激光脉冲的相对能量。给出了光纤激光器在驱动电流分别为6A,7A和8A时衰减后的ASE噪声廓线以及ASE噪声占激光脉冲能量的比例。     

回音壁微腔激光器噪声特性数值模拟研究(特邀)

通过建立包含朗之万噪声源的三模速率方程模型,模拟研究了回音壁模式微腔激光器的噪声特性和线宽特性,特别是注入电流热效应引起的跳模及其对光功率和实现窄线宽的影响.回音壁微腔激光器单模工作时,在大偏置电流下可由低频处的频率噪声得到百kHz以下的激光器线宽;在微腔双模激射状态下,由于模式竞争作用,微腔激光器的相对强度噪声和频率...     

高功率光纤激光器中ASE噪声的测量方法（英）

高峰值功率脉冲光纤激光器在激光雷达系统中有着广泛的应用。然而,光纤激光器中放大自发辐射噪声（ASE）严重影响了系统的探测性能。提出一种测量高峰值功率脉冲光纤激光器中ASE噪声的方法。在该方法中,首先对高峰值功率的激光脉冲衰减,然后在时域分别测量和计算ASE噪声和激光脉冲的相对能量。给出了光纤激光器在驱动电流分别为6 A,7 A和8 A时衰减后的ASE噪声廓线以及ASE噪声占激光脉冲能量的比例。     

减反膜外腔半导体激光器特性的研究

研究了镀减反膜GaAs半导体激光器在Littrow 式外腔结构中的输出特性.采用电流补偿技术,得到了约30 GHz的连续无跳模调谐范围.利用外差拍探测技术获得激光器输出线宽约为120 kHz.还研究了激光器的强度噪声分别随着电流与波长变化的特点并对此进行了分析.该类激光器可以广泛应用在冷原子物理、激光光谱以及量子光学等许多领域. 关键词： 减反膜 半导体激光器 线宽 强度噪声     

用速率方程分析垂直腔面发射激光器的噪声

采用一种合理的噪声模拟方法，用速率方程对垂直腔面发射激光器的噪声特性进行了数值分析，在单模情况下计算了器件的自发辐射因子、输出功率、注入电流、阈值电流等参数与相对强度噪声、频率噪声以及线宽等特性的关系，计算结果与实验基本相符，对优化垂直腔面发射激光器的结构设计和应用条件有所裨益. 关键词：     

Current spreading effects in 680-nm-band self-sustained pulsating AlGalnP visible laser diodes

We have developed 680-nm-band AlGalnP visible laser diodes having very lowintensity noise with stable self-sustained pulsation. The pulsation characteristics were affected by current spreading outside the ridge stripe. We obtained AlGalnP visible laser diodes with stable self-sustained pulsation by optimizing the ridge structure. The lasers achieved relative intensity noise (RIN) as low as-136 dB Hz^–1 in the temperature range 20–50°C at 3 mW.     

The noise equivalent circuit model of quantum-dot lasers

We derive the noise equivalent circuit model of semiconductor self-assembled quantum-dot (QD) lasers (SAQDL) from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise of an SAQDL combined with electronic components. Using the presented model, we study how the carrier dynamics influences relative intensity noise (RIN) of QD lasers. We demonstrate that RIN is degraded with larger inhomogeneous broadening. Furthermore, we show that RIN is enhanced for lower quantum-dot coverage level.     

Study of the optical feedback-induced noise in semiconductor lasers and applications to the optic disc system

The dynamics and noise of semiconductor lasers under optical feedback (OFB) have been simulated. The study is performed as applied to an optic-disc system in which laser radiation is reflected by the disc surface and re-injected into the laser cavity. We examine the possibility of suppressing OFB-induced noise in the optic-disc system by the technique of superposition of high-frequency current. The study is based on numerical integration of the time-delay rate equations of semiconductor lasers under OFB. The laser noise is evaluated in terms of the spectral profile of relative intensity noise (RIN). It is shown that RIN is enhanced when states of chaos are generated, and attains minimum levels under continuous-wave operation just before the laser starts the route to chaos. The suppression of RIN in the low-frequency regime is achieved when the superposition-current frequency exceeds the laser resonance frequency by factors of 0.8, 1.0, and 1.1 and when the modulation depth exceeds 0.4.     

Harmonic and intermodulation distortions and noise associated with two-tone modulation of high-speed semiconductor lasers

We present results of modeling and simulation of the harmonic and intermodulation distortions as well as the intensity noise of high-speed semiconductor lasers under two-tone modulation. Multiple quantum-well lasers are considered, which are characterized by large differential gain and a modulation bandwidth of about 25GHz. The study is based on the rate equation model of semiconductor lasers excited by injection current with two sinusoidal tones separated by a radio frequency. The modulated laser signal is modeled in both the time and frequency domains. The time domain characteristics include the fluctuating waveform, while the frequency domain characteristics include the frequency spectrum of the relative intensity noise (RIN), carrier-to-noise ratio, modulation response, harmonic distortion, and the second- and third-order intermodulation distortions (IMD2 and IMD3). The analysis is performed for three frequencies of 5, 15, and 24 GHz, which are, respectively, lower, comparable, and higher than the laser relaxation frequency. The range of the modulation depth covers the regimes of small and large-signal modulation. We show that both RIN and IMD3 of two-modulated laser are minimum when the modulation frequency is 5GHz, and maximum when the modulation frequency is 24 GHz. The second-order harmonic distortion, IMD2, and IMD3 values are larger in the vicinity of relaxation oscillations and increase with the modulation index, especially under large-signal modulation.     

Analysis of the relative intensity noise behaviour in tunable two- and three-section distributed Bragg reflector lasers

A theoretical analysis is made of the relative intensity noise (RIN) in tunable two- and three-section distributed Bragg reflector (DBR) lasers by taking into account the actual frequency dependence of the Bragg reflector. The RIN is shown to depend significantly on the tuning current, especially at low frequencies and for low and moderate values of the grating coupling coefficient. For high values of this coefficient the dependence is insignificant when the tuning is performed through the DBR section, in accordance with the experimental results recently reported. The RIN spectrum is more significantly affected, however, when the phase control current in the three-section device is used for tuning.     

Noise conversion from pump to the passively mode-locked fiber lasers at 1.5 μm

We characterize the noise conversion from the pump relative intensity noise (RIN) to the RIN and phase noise of passively mode-locked lasers at 1.5 μm. Two mode locking mechanisms, nonlinear polarization rotation (NPR) and semiconductor saturable absorber mirror (SESAM), are compared for noise conversion for the first time. It is found that the RIN and the phase noise of both types of lasers are dominated by the noise converted from the pump RIN and thus, can be predicted with the measured pump RIN and noise conversion ratios. The SESAM laser is found to show an excess noise conversion from the laser RIN to the laser phase noise due to the slow saturable absorber effect.     

Manifestation of 1/<Emphasis Type="Italic">f</Emphasis> leakage noise in nanoscale light-emitting structures

We present the results of studies of the 1/f noise spectrum in light-emitting diodes and lasers with nanoscale structures based on GaAs and its solid solutions. Leakage current was detected from an analysis of I–V characteristics and voltage noise spectrum dependences on the current. Leakage current appeared to be the main source of noise in the samples and leads to intensity fluctuations of the spontaneous radiation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 2, pp. 149–161, February 2008.     

微腔半导体激光器的两种新调制方法

本文提出微腔半导体激光器的两种新调制方法:自发发射寿命调制和光子寿命调制。小信号近似分析的数值模拟结果表明,这两种调制方法的调制带宽大于同参数下的电流调制的带宽。     

Pump-to-Stokes transfer of relative intensity noise in Brillouin fiber ring lasers

We have experimentally investigated pump-to-Stokes intensity noise transfer in both the frequency domain and the time domain in all-fiber single-frequency Brillouin ring lasers. In the high-frequency region (>1MHz), the pump-to-Stokes noise transfer function can be much smaller than unity, indicating that the Brillouin fiber lasers act as an efficient low-pass filter. The maximum noise reduction of 40-60 dB was observed at antiresonant frequencies that are multiples of half the cavity free spectral range. This is the first experimental demonstration, to the authors' knowledge, of intensity noise reduction in Brillouin fiber lasers.     

Free-running frequency stability of mid-infrared quantum cascade lasers

The intrinsic frequency fluctuations of two single-mode quantum cascade (QC) distributed-feedback lasers operating continuously at a wavelength of 8.5 mum are reported. A Doppler-limited rovibrational resonance of nitrous oxide is used to transform the frequency noise into measurable intensity fluctuations. The QC lasers, along with recently improved current controllers, exhibit a free-running frequency stability of 150 kHz over a 15-ms time interval.