机载大功率半导体激光信标系统设计

为配合地面探测跟踪系统对飞行目标的探测,设计了一种以４０ Ｗ 紧凑型半导体激光器为光源、具有一定发散角的机载式单色信标系统。由于系统要满足机载平台加装体积小、质量轻、散热好的要求,设计了一体成型的鳍片式壳体结构,解决系统散热问题的同时,控制了整体质量。为实现在有限体积内,４０ Ｗ 单阵列光纤耦合半导体激光器模块所需的６０A 大电流恒流驱动,采用叠相调制技术和同步ＢUＣＫ 变换电路结构;为解决激光器在高空低温环境下输出光功率和中心波长能够稳定控制的难题,设计了数模混合双向温控系统。利用ＺEMAX 软件设计了双凹透镜组结构的扩束装置,实现了对激光发散角的发散和可调节。通过环境考核测试,系统在０℃～１５℃的低温环境下,输出光功率稳定度和波长控制精度均能满足要求。     

Closed-loop phase-shifting interferometry with a laser diode

A closed-loop phase-shifting Fizeau-type interferometer at lambda=633 nm was constructed with the direct frequency modulation of laser diodes. The interferometer is servo controlled fully in the phase domain where optical phases are detected by a two-frequency optical heterodyne method. Stepwise phase shifting was accomplished with good stabilization against external disturbances (vibration, air flow, etc.) and laser frequency fluctuations.     

激光系统中半导体激光器温度稳定系统研究与设计

激光器系统中半导体激光器的功率输出稳定度和工作温度有很大的关系,为了使大功率半导体激光器输出功率稳定,需要对激光器实现高精度、快速温度控制。针对现有的激光系统中激光器温度控制系统存在控制精度不够高、控制速度慢等问题,设计了一种温度稳定系统,采用PT-100热电偶测量激光器温度,并使用最小二乘法对温度数据进行拟合,使得温度测量精度达到0.01 ℃;使用改进粒子群算法优化(PSO)的PID控制器实现温度控制。仿真实验和实际测试表明,所设计的温度稳定系统能够很好地控制激光器温度,达到目标温度所需的调节时间小于11 s,达到稳态后温度波动在±0.02 ℃内。与传统的温度控制方式相比,所设计的系统能够实现参数自整定并自动调节温度,对大功率激光系统中激光器温度具有良好稳定效果。     

Quantum design of semiconductor active materials: laser and amplifier applications

We present an overview of a novel first‐principles quantum approach to designing and optimizing semiconductor quantum‐well material systems for target wavelengths. Using these microscopic inputs as basic building blocks we predict the light‐current (LI) characteristic for a low power InGaPAs ridge laser without having to use adjustable fit parameters. Finally we employ these microscopic inputs to develop sophisticated simulation capabilities for designing and optimizing end packaged hi gh power laser structures. As an explicit example of the latter, we consider the design of a vertical external cavity semiconductor laser (VECSEL).     

Proposal of a semiconductor ring laser gyroscope

We proposed a novel optical inertial rotation sensor using a semiconductor ring laser (SRL). The frequency difference between the two counter propagating oscillation frequencies was automatically generated in a mechanically rotated SRL, which consisted of a pig-tailed laser diode amplifier module. And the Sagnac frequency shift could be detected at the first time as a beat note by the terminal voltage change of the SRL without branching the circulating optical power. These experimental results verify that an SRL operates as an optical inertial rotation sensor based on the Sagnac effect.     

Far-field emission of a semiconductor nanowire laser

The polarization properties and angular distribution of intensity of the far fields from a nanowire laser are investigated. The far-field emission depends strongly on the mode type (HE11, TE01, TM01) and the radius of the nanowire. The emission is weakly directional, and a large part of it can be emitted in the backward direction. Our results can be applied for experimental determination of a lasing mode by its far fields as well as for optimization of laser emission.     

Experimental control of a chaotic semiconductor laser

We have experimentally controlled the chaotic output of a single-mode semiconductor laser pumped near threshold and subject to optical feedback. We used a novel technique called dynamic targeting, which was theoretically proposed by Wieland et al. [Opt. Lett. 22, 469 (1997)]. Optical feedback causes the semiconductor laser to undergo a bifurcation cascade that exhibits regions of stability, periodicity, chaos, and coherence collapse. By adjusting the feedback phase simultaneously as the feedback strength was varied we steered the laser into the stable maximum gain mode, and thus we stabilized the system at maximum intensity.     

Model of lock-in in a ring laser and a semiconductor laser gyro

It is assumed that the process of lock-in in a ring laser has a finite transient time. This assumption serves as a basis for developing a semiconductor laser gyro. A semiconductor optical amplifier is applied as an amplifying medium, and a ring resonator represents a long optical fiber. The injection of an external single-frequency light into a ring resonator with subsequent circulation of counterpropagating waves is used. The light characteristics of the semiconductor laser gyro are discussed, and the rotation sensitivity of the gyro is demonstrated.     

Raman fiber laser pumped by a semiconductor disk laser and mode locked by a semiconductor saturable absorber mirror

A 1.6μm mode-locked Raman fiber laser pumped by a 1480nm semiconductor disk laser is demonstrated. Watt-level core pumping of the single-mode fiber Raman lasers with low-noise disk lasers together with semiconductor saturable absorber mirror mode locking represents a highly practical solution for short-pulse operation.     

Continuous-wave Raman laser pumped within a semiconductor disk laser cavity

A KGd(WO?)? Raman laser was pumped within the cavity of a cw diode-pumped InGaAs semiconductor disk laser (SDL). The Raman laser threshold was reached for 5.6 W of absorbed diode pump power, and output power up to 0.8 W at 1143 nm, with optical conversion efficiency of 7.5% with respect to the absorbed diode pump power, was demonstrated. Tuning the SDL resulted in tuning of the Raman laser output between 1133 and 1157 nm.     

Electrical pumping of a third-order mode semiconductor laser

AlGaAs-based quantum well laser structures with third-order waveguide mode emission at 775 nm are a promising route toward compact twin-photon sources at 1.55 μm based on the principle of modal phase matching between the pumping frequency and fundamental modes at half frequency in III–V semiconductor waveguides. Following the demonstration and characterization of an optically pumped third-order mode semiconductor laser, in this paper we present data of the corresponding structure under conditions of electrical pumping. By pumping electrically and optically the same sample made for current injection, identical transverse far-field angular laser mode profiles are measured and with very low parasitic losses. Although they do not follow the third-order mode emission pattern as it is expected, however this means that the different way of pumping, that of the electrical one as compared to optical pumping is not responsible for the absence of third-order mode emission. Furthermore, since the undoped optically pumped laser sample correctly emits on the third-order mode, it is concluded that the cladding layers of the structure still need to be optimized in doping and thickness, in order to reduce the internal losses for the third-order mode.     

Transformation of laser light by a semiconductor microcylinder

Theoretical simulation of the transformation of the electromagnetic field by microcavities in the shape of homogeneous semiconductor microcylinders has shown that the morphology of microcavities affects the transformation of the optical radiation in modes of the microlaser in a rather complicated way. We show that, in homogeneous semiconductor microcylinders, there can be realized the regime of single- or two-mode lasing on morphological resonances differing both by the quality factor and by the spatial structure of the electromagnetic field. The region of single- or two-mode lasing is determined by the ratio of the gain and loss factors and by the field magnitudes in the spatial structure of morphological resonances.     

The optimal design for weak optical feedback semiconductor laser with frequency modulation

In this paper the frequency modulation characteristics the semiconductor laserwith weak optical feedback are presented,considering both the frequency deviation and thespurious intensity modulation.The frequency modulation can be realized without spurious in-tensity modulation under proper feedback conditions.There is an optimal feedback intensity tomaximize the frequency deviation.     

Anatomy of a polarization switch of a vertical-cavity semiconductor laser

Using a streak camera we have measured the three Stokes polarization parameters during a polarization switch of a vertical-cavity semiconductor laser. The switch occurs along a corkscrew path on the Poincare sphere and takes on average a few nanoseconds; this value agrees with a theoretical treatment based upon the Fokker-Planck equation.     

Frequency bistability of a semiconductor laser under a frequency-dependent feedback

The emission frequency of a diode laser submitted to a frequency-dependent optoelectronic feedback is observed to have more than one stable operation point together with a stable power emission. This is, to our knowledge, the first observation of bistability exclusively in the frequency of an optical system. The experiment was carried out with a semiconductor laser coupled to the cesium D2 line by an orthogonally polarized frequency-sensitive optical feedback.     

A new model for a mode-locked semiconductor laser

We consider a new model for passive mode locking in a semiconductor laser comprising a set of delay differential equations. Bifurcations leading to the appearance and break-up of the mode-locking regime are studied numerically.     

Excitability in a semiconductor laser with saturable absorber

We show that a monolithic and compact vertical cavity laser with intracavity saturable absorber can emit short excitable pulses. These calibrated optical pulses can be excited as a response to an input perturbation whose amplitude is above a certain threshold. Subnanosecond excitable response is promising for applications to novel all-optical devices for information processing or logical gates.     

列阵半导体激光器的噪声

重点报道列阵GaAs-AlGaAs激光器相对强度噪声的测量结果,并和单元器件作了比较.实验测量包括相对强度噪声和驱动电流、调制频率以及温度的关系,并验证了在这些情况下相对强度噪声在激光器处于阈值时具有最大值的理论予言.