半导体激光器稳频技术

窄线宽稳频激光器在精密干涉测量、光学频率标准、激光通信、激光陀螺、激光雷达、基本物理常数测量和冷原子系统等研究领域有着广泛的应用。自由运转的半导体激光器每天的频率漂移量可以达到GHz,因此研究半导体激光器的稳频具有十分重要的意义。以780 nm的半导体激光器稳频为例,介绍了目前广泛使用的各种半导体激光稳频技术的基本原理及试验方案,如消多普勒饱和吸收光谱稳频技术、消多普勒双色谱稳频技术、调制转移谱稳频技术、调频光谱稳频技术和频率-电压转换稳频技术,并对各种稳频方法的性能和特点进行了分析。     

基于相干包络解调的窄线宽测量算法研究

激光线宽对光学相干探测系统的探测范围、精度和噪声特性都有重要影响。为精确测量半导体激光器的线宽值,提出了通过解调短延时自外差的干涉谱来实现高精度窄激光线宽测量的新方法。搭建短延时的自外差干涉测量系统,得到半导体激光器的干涉谱,通过设计算法对干涉谱的相干包络进行解调,最终获得了严格的洛伦兹线型谱和相应的谱线宽度,通过理论分析、仿真和实验验证了该方法的可行性。该方法可以忽略因1/f频率噪声产生高斯展宽带来的影响,与传统线宽测量方法相比,该方法的测量结果更加精确。     

具有外部光学反馈激光器的动力学稳定性

具有外部光学反馈激光器,如加外腔镜的半导体激光器等,被广泛应用于光通讯及其它的基础光学研究中。本文对具有外部光学反馈激光器动力学模型进行了讨论。并从具有外部光学反馈的半导体激光方程出发,对其动力学稳定性进行研究,得到稳定性条件、稳     

半导体激光器的外光学反馈效应的理论分析

本文研究了半导体激光器的外光学反馈效应，应用Lang-Kobayashi方程，分析求解了半导体激光器在外腔反馈条件下激光频率和光强的输出变化特性。     

基于利特罗式激光反馈光栅干涉的微位移测量技术

通过在激光反馈干涉(LFI)系统中引入衍射光栅,提出了一种基于利特罗结构的激光反馈光栅干涉(LFGI)技术,用于一维和二维精密位移的测量。半导体激光器出射的光束以利特罗条件入射至反射式全息光栅,衍射光沿入射光方向返回激光腔后,腔内会发生激光反馈干涉效应。引入正弦相位调制解调技术,高精度地测量一维和二维微位移。利特罗结构和LFGI系统具有自准直性好、结构紧凑、易于操作和系统稳定性高的优点。实验结果表明,利特罗式LFGI系统的位移测量精度可以达到10 nm量级。     

半导体激光器的原子法拉第反常色散光学滤波器光反馈稳频

为提高半导体激光器的频率稳定性，利用原子法拉第反常色散光学滤波器（FADOF）超窄带的选频透射特性，将其置于半导体激光器的外腔中作选频元件，采用光反馈的方法，使得透射率低的激光频率分量被抑制，透射率高的激光频率分量被加强，有效地实现了光反馈激光稳频。利用Cs原子法拉第反常色散光学滤波器工作于D2线852nm的4峰窄带透射状态。通过调节半导体激光器的温度和电流，调谐半导体激光器的输出波长，将激光器锁定在任何一个透射峰上，用26％的光反馈量，使稳频后的激光频率长期稳定性保持在75MHz／2h以内，而且采用这种稳频方法的输出激光中心波长一直稳定在频率基准上，没有单方向漂移。同时，还实现了Cs原子法拉第反常色散光学滤波器稳频半导体激光器结构的一体化，使其具有实用性。     

一种调频连续波干涉仪激光波长稳定性测量方法

针对调频连续波干涉测量系统中半导体激光光源存在波长漂移的问题,提出了一种基于干涉腔的调频连续波激光波长稳定性测量方法。首先推导了波长漂移量的测量理论,确定了位移-波长漂移量的变化系数,然后设计了拍频信号波长漂移量的解调算法,最后搭建了调频连续波干涉腔测量系统并进行了实验验证。结果表明,波长漂移量的测量分辨率为0.016 pm,波长漂移解算速度达50/s（测量时间为0.02 s）,相比光学拍频法和干涉比较法,测量速度有较大的提高。激光器持续工作1 h,测量标准差为0.049 pm,平均中心波长稳定性在0.19×10^-6内。该方法在光纤传感和精密干涉测量领域有较好的应用价值。     

半导体激光器的噪声和带宽的测量

半导体激光器广泛地应用于光学测量、激光雷达、机载陀螺仪、信息处理、光通信、激光光谱和激光抽运原子频标等领域。在这些应用中半导体激光器的噪声和带宽是十分重要的参数,必须进行测量。本文详细地介绍了在激光抽运铷频标研制过程中激光器的噪声和带究的测试方法及实验结果。     

光纤通信用半导体激光器

半导体激光器是光纤通信用的主要光源,由于光纤通信系统具有不同的应用层次和结构,因而需要不同类型的半导体激光器。文章根据目前光纤通信系统的发展趋势,介绍几种典型的光纤通信用半导体激光器件———法布里-珀罗激光器、分布反馈半导体激光器、电吸收型调制器集成光源、波长可选择光源、垂直腔面发射激光器的特点和发展方向。     

短相干半导体激光器的射频调制特性及应用

短相干激光光源在进行高精度的干涉测量时,可以消除被测光学元件前后表面反射形成的杂散光,是低相干干涉仪的理想光源。针对低相干干涉应用对光源的需求,依据速率方程和激光调制特性对射频调制下的短相干半导体激光器光谱特性进行了理论研究。搭建了短相干光源系统,研究了半导体激光器斜率效率η、偏置电流I_b、射频信号频率f_m和幅度A_m对其相干长度的影响。实验结果表明,斜率效率大的半导体激光器更有助于短相干特性的实现,随着调制信号频率和幅值增加,工作在阈值附近的激光器相干长度随之降低,该系统在I_b=1.3Ith、f_m=950 MHz、 A_m=19 dBm的条件下获得了相干长度为90μm的短相干光源。并成功应用于斐索干涉仪上,获得了对比度K=0.931 8的清晰干涉图像,与现有短相干光源相比,对比度提高了约51.1%,实现了对平行平板玻璃面形的测量。     

半导体激光自混合干涉的弱光反馈模型

文章针对弱光反馈情形，对基于光反馈效应的激光自混合干涉模型进行了探讨。采用双空模型，从增益阈值和振荡效率方面给出了理论模型。该模型很了地解释了激光自混合干涉现象。最后分析了一实用光纤自一干涉系统的数学模型。     

引入激光回馈的双光束干涉效应的研究

提出了一种引入He-Ne激光回馈的双光束干涉系统,并在理论和实验两方面进行了研究。实验中对系统中的干涉信号及激光器尾光功率变化同时进行探测。发现当干涉仪的主回馈镜移动时,激光器尾光信号是正弦形波形,而干涉仪输出的是以双峰为一个周期的信号,双峰中一峰总是高于另一峰,并且当主回馈镜移动方向改变时,同一周期中两峰出现的顺序也随之改变。对实验现象进行了理论分析,并模拟出干涉信号及激光自身功率的变化曲线。理论分析及模拟结果与实验结果完全吻合。讨论了利用发现的现象进行测量的可行性,所提出的测量方法易于实现。     

激光回馈干涉进展及其生物医学应用综述

激光回馈干涉具有共光路、精度高等优势,已经成为光学测量领域的研究热点。基于激光回馈干涉的理论及主要模型,根据外界反射物信息分析反射光特性,得到激光回馈干涉的测量方法,通过分析激光输出特性的变化实现外界反射物体的信息测量。针对粗糙表面物体或流体,激光回馈干涉结合散斑技术发展为激光回馈散斑干涉技术;针对光滑表面物体,激光回馈干涉在离轴短外腔下出现多重激光回馈干涉现象。激光回馈干涉技术在位移、角度、速度、成像等检测领域快速发展。激光回馈干涉能够检测粗糙表面的弱反馈光且灵敏度高,同时兼具传统干涉技术的高精度优势,在生物医学领域的非接触测量具有研究价值和应用前景。     

Optical feedback effects on the spectral linewidth of semiconductorlaser sensors using self-mixing interference

The spectral characteristics of a semiconductor laser are significantly affected by optical feedback in the active cavity of the diode. In this paper, the influence of weak optical feedback on the linewidth is examined and a new relationship proposed. Feedback-induced changes in the power spectral density are also determined by a theoretical analytical model, in good agreements with experiments. These results are then discussed for sensing applications using self-mixing interference, as the maximum range of distance and displacement sensors can be limited by half the coherence length of the laser diode modified by the optical feedback     

相位凝固技术中干涉信号调制解调误差分析

为了进一步减小基于相位凝固技术的激光反馈干涉系统测量运动物体微位移时的测量误差,采用MATLAB数值仿真及曲线拟合的方法,对移相间隔和外腔反射面振动幅度引起的系统误差进行了理论分析。在系统实验中依据相位凝固原理对物体运动产生的干涉信号进行采样,获取多组光功率曲线,在光功率曲线上实时判向并标记特征点。根据特征点重构被测物体的微位移曲线,对重构得到的微位移台阶曲线进行多项式拟合以提高测量精度。结果表明,在固定移相间隔为/5、激光器波长为1550nm的情况下,测量分辨率优于/20(77.5nm),实际测量的绝对误差最大值为47.98nm,峰峰值误差平均值小于1nm。相位凝固技术调制解调干涉信号为微位移的方向辨识和高精度测量提供了新的解决方案。     

Distributed Feedback Lasers Based on Thiophene/Phenylene Co‐Oligomer Single Crystals

Organic crystals have great potential for the applications in laser devices. This article presents an effective approach for fabrication of distributed feedback single crystal lasers. With the laser interference ablation method, high quality grating structures have been fabricated on the organic single‐crystalline thin film materials. The relationship between the depth, periodicity, and laser fluence is discussed. The optical properties, such as photoluminescence, and diffractive properties are studied in detail. With the appropriate period, strong laser emission has been observed from these devices. Distributed feedback lasing is demonstrated from the laser interference ablated organic single crystals for the first time.     

Increasing acceptable number of signals in subcarrier multipleaccess optical networks in the presence of high optical beatinterference

This paper theoretically and experimentally demonstrates that our proposed method improves the carrier-to-noise ratio (CNR) of subcarriers and significantly increases the number of acceptable optical signals in subcarrier multiple access (SCMA) systems using distributed feedback laser diodes (DFB-LD's) with the same center optical frequency. This method reduces optical beat interference by using the multiplied product of the subcarriers and a low-frequency signal. From the experimental results using 1.3 μm DFB-LD's, the CNR sufficiently satisfies the required level even if the number of optical signals is three. Theoretically, the number of acceptable optical signals increases as LD's with wider optical line-width or with greater chirp coefficient are used. For example, assuming a laser chirp coefficient of 540 MHz/mA, the maximum number of LD's that can be used while still meeting the minimal CNR requirement is 12. This number corresponds to 66 optical beat interferences. Thus, this proposed beat-interference reduction technique is very effective in SCMA systems using DFB-LD's without optical frequency control     

Synchronized Generation of Reconfigurable Microwave Sinusoidal Wave Packets From a Free-Running Pulsed Laser

Generation of customized microwave sinusoidal wave packets precisely synchronized with a free-running pulsed laser is required for many electrooptic modulation-based optical pulse processing and measurement applications. We propose and experimentally demonstrate a simple technique for this purpose. This technique is based on optical frequency-to-time conversion of a spectral interference in a fiber-optic two-arm interferometer with a wavelength-dithering feedback control. The same platform can be used to operate over a wide range of input repetition rates and can be optically reconfigured for tuning the frequency, amplitude, and phase of the generated microwave sinusoids.     

Self-mixing interference inside a single-mode diode laser foroptical sensing applications

This paper presents a theoretical analysis and a comparison with experimental results on self-mixing interference inside a single-longitudinal-mode diode laser. A theoretical model, based on the steady-state equations of the lasing condition in a Fabry-Perot type laser cavity, is described, and through it a satisfactory analysis of self-mixing interference for optical sensing applications is given. In this work, the self-mixing interference produced by an external optical feedback is found to be due to the variations in the threshold gain and in the spectral distribution of the laser output. The gain variation results in an optical intensity modulation, and the spectral variation determines both the modulation waveform and the coherence properties of the interference. The theoretical analysis of the self-mixing interference is seen to yield a simulation of the laser power modulation which is in good agreement with the experiment results reported     

收发一体式激光测速仪光反馈噪声的抑制

针对一种收发一体式激光测速仪信噪比低,导致灵敏度差的问题,提出了针对收发一体式激光测速仪光反馈噪声抑制的方法。通过调整出射窗角度来减少镜面反射,增加光阑减少进入半导体激光器中的杂散光光通量,调节原向反射屏与半导体激光器间的相对位置关系等具体方法,有效地降低了光反馈噪声对信号的影响。验证实验表明通过对光反馈噪声的抑制,较好地改善了测试系统的信噪比,在工程实践中可提高该系统的动态范围以及小信号的识别能力。