调制与非调制的半导体激光器典型稳频方法对比分析

针对半导体激光器稳频技术中的饱和吸收法、塞曼调制法、基于原子二向色性的激光器锁定(DAVLL)法和去除多普勒背景的二向色性锁定(DFDL)法4种典型稳频方法进行了稳定性、操作性、抗干扰能力等方面的对比分析,概括了调制和非调制稳频方法的优缺点,为相关实验选择合适的稳频方法提供依据。     

全光Cs原子磁力仪的温度特性研究

全光铯(Cs)原子磁力仪是一种高灵敏度弱磁检测仪,核心器件Cs原子气室的工作温度直接决定了原子磁力仪的灵敏度。实验系统中采用频率锁定在Cs原子D1线F=3→F′=4共振线的圆偏振光极化Cs原子,检测光采用频率锁定在Cs原子D2线F=4→F′=5共振线的线偏振光,检测介质的圆二向色性。实验发现,随着Cs原子气室工作温度的升高,磁力仪输出信号幅度先增加然后逐渐衰减,而磁力仪的线宽近似线性增加。实验测试了温度由25℃升高至45℃时的磁力仪输出信号,结果表明:当温度为37.6℃时,原子磁力仪达到最佳灵敏度。     

基于塞曼效应的半导体激光器锁频系统设计

半导体激光器在原子干涉仪、原子钟、精密测量等领域应用日趋广泛,而其输出光频率易受外界环境温度等影响发生偏移。分析了利用塞曼效应锁定半导体激光器频率的原理,搭建的锁频实验系统中选用Newfocus(TLB-6017,853 nm)可调谐激光器、铯原子注入气室。调节外加磁场大小的同时监测铯原子超精细能级分裂情况,找到适合锁频的铯原子D2线F=4→F′=5吸收峰,经过多次闭环测试,验证了该稳频系统的可靠性,稳定度较高,且系统简单易操作,一小时内激光稳定度为28 MHz,短期激光稳定度为18 MHz。     

双频激光干涉仪在长度测量中的应用

一、双频激光干涉仪简介 双频激光干涉仪的光源是一支置于强度为200～300高斯的纵向磁场中的单模氦氖气体激光器,如图1a)所示。由于塞曼效应,激光器的谱线分裂为频率分别为v1和v2的主旋和右旋圆偏振光。其增益曲线如图1b)所示。对激光器进行稳频控制后,若谐振频率被控制在v0处(     

环形激光器双光路椭圆度测量系统

针对通过测量输出光椭圆度对环形激光器进行调腔的要求,研究并建立了环形激光器双光路椭圆度测量系统.计算分析了无源环形腔对S线偏光和P线偏光的频率响应特性,得出S线偏光谐振峰频率特性更适于无源环形腔的稳频.采用S线偏光作为外部输入光来提高稳频精度,搭建了环形激光器双光路稳频与测量系统.环形激光器稳频系统在10 s内就能完成稳频,稳频效率高,稳频后光强波动幅度为1.8％.提出的椭圆度测量方法使椭圆度变化幅度约为0.65％,减小了光强波动对测量精度的影响.实验显示,构建的测量系统可满足椭圆度测量的要求.     

双纵模激光器的热稳频控制系统的研究

介绍了双纵模热稳频控制系统的构成、原理及系统建模,并引入自适应算法提高稳频精度,缩短稳频时间,经实验验证,证明该系统对双纵模激光器的热稳频控制是实用的.     

计算机监控FBG-ECLD乙炔吸收稳频技术

报道了基于计算机监控的光纤光栅外腔半导体激光器(FBG-ECLD)乙炔吸收稳频,设计了计算机信号监测和设备控制的平台,实现了在计算机界面上对信号的监测和对稳频控制设备的控制。系统将光纤光栅外腔半导体激光器的输出光频率稳定在乙炔的一个吸收峰上,稳定度达到10-8量级。     

全内腔Nd:YVO4微片激光器稳频研究

研究了全内腔Nd:YVO4微片激光器的温度稳频控制。分析了影响Nd:YVO4微片激光器频率的因素和频率变化对系统测量误差带来的影响。设计了合理的机械结构和控制电路,通过采用温度控制的方法进行稳频,介绍了系统的组成成分及各个元件的作用。实验分析了频率和输出功率之间的关系,在此基础上优化了系统的结构。实现稳频控制后,显著提高了激光器的频率稳定性,频率稳定度能达到(10^-7~10^-8),改进了系统的工作性能,以满足高精度的测量需求,使其在精密测量技术领域具有更广阔的发展前景。     

激光二级管泵浦KTP腔内和频激光器及噪声特性的分析

给出了采用了激光二极管泵浦Nd:YVO₄晶体产生1064nm与1342nm双谱线振荡的实验研究,通过KTP晶体II类相位匹配腔内和频产生输出波长为593.5nm的橙黄色激光的实验.在不同泵浦功率下,测量和分析了该激光器的噪声特性.根据和频激光器输出的纵模结构测量结果与和频光耦合波方程,研究了和频激光器的噪声与参与和频的基频光纵模之间的关系.结果表明:对于激光二极管泵浦Nd:YVO₄激光晶体,KTPII类位相匹配腔内和频激光器,如参与和频的2个波长中有一个波长为单纵模工作,尽管和频光输出为多个纵模,该激光器的输出仍为低噪声状态.如参与和频的2个波长全为多纵模,和频光输出为高噪声状态.在腔内和频过程中,虽然没有倍频过程中的和频引起模式竞争,但参与和频2个基频光的不同模式间的交叉和频和同一波长的不同模式间的增益饱和,也产生了与绿光问题类似的输出噪声和不稳定状态,但噪声特性要好于同类的腔内倍频激光器.     

Fe-Ga磁特性测试装置改进与动态磁致伸缩实验

利用Fe-Ga磁特性测试装置进行动态磁致伸缩测量时,受激励线圈产生的磁场的影响,测试样品的应变通常偏大,本文对此做了分析并进行验证。通过分析Fe-Ga动态磁致伸缩测量过程,对原测试装置进行了改进。将样品的一端固定在极头上并调节激励磁场使其在样品饱和磁场附近,以消除机械振动对动态磁致伸缩测试产生的影响。采用多参数磁学测试系统和改进前后的Fe-Ga特性测试系统进行Fe-Ga静态和动态磁致伸缩特性测试实验。结果表明:采用改进的Fe-Ga磁特性测试装置可在低饱和场下精确测量动态应变。实验还测试了Fe-Ga在2.7kA/m偏置磁场作用下的动态磁致伸缩特性,结果表明:(1)偏置磁场作用下应变与磁场同频;(2)应变对磁场的滞后随磁场频率的增加而增大;(3)λ~H曲线为椭圆形且椭圆环的面积随频率的增大而增大。上述结果表明,本文提出的改进装置可有效消除振动产生的额外应变。     

Small-sized dichroic atomic vapor laser lock

Two, lightweight diode laser frequency stabilization systems designed for experiments in the field are described. A significant reduction in size and weight in both models supports the further miniaturization of measurement devices in the field. Similar to a previous design, magnetic field lines are contained within a magnetic shield enclosing permanent magnets and a Rb cell, so that these dichroic atomic vapor laser lock (DAVLL) systems may be used for magnetically sensitive instruments. The mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long) and does not require cell heaters. An even smaller micro-DAVLL system (9 mm long) uses a microfabricated cell (3 mm square) and requires heaters. These new systems show no degradation in performance with regard to previous designs while considerably reducing dimensions.     

A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium

The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D(2) transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude.     

线性调频半导体激光定位的研究

本文提出了一种新的半导体激光定位技术,它利用半导体激光器的线性调频特性来实现干涉零点的动态定位。突破了传统白光定位的局限,简化了干涉仪设计,并实现了大范围内的零点捕捉,是一种实用的干涉定位技术。     

Magnetooptical resonances in cells with residual buffer gas in elliptical polarization of radiation

The dependence of the fluorescence intensity of Cs vapor irradiated by elliptically polarized light resonant with the F = 4 ?? F = 5 transition on the scanned magnetic field has a complex shape ?? a narrow dip against the background of a broad peak. It is found experimentally that the dip is due to the small component of the magnetic field orthogonal to the direction of the laser beam. A two-level atom model with degenerate angular-momentum states predicts an order of magnitude lower contrast of this dip. The experimentally observed contrast of the dip can be explained by assuming that due to the low buffer-gas pressure in the optical cell, part of the resonant atoms is able to return to the laser beam without thermalized collisions with the wall of the cell, increasing the contrast. In addition, accounting for all optical transitions of the D ₂-line and the optical pumping of the hyperfine-structure components of the ground state is a fundamental point for the interpretation of the experimental results.     

Phase-locked laser system for use in atomic coherence experiments

We describe a phase-coherent laser system designed for use in experiments involving coherently prepared atomic media. We implement a simple technique based on a sample-and-hold circuit together with a reset of the integrating electronics that makes it possible to scan continuously the relative frequency between the lasers of over tens of gigahertz while keeping them phase locked. The system consists of three external-cavity diode lasers operating around 795 nm. A low-power laser serves as a frequency reference for two high-power lasers which are phased locked with an optical phase-locked loop. We measured the residual phase noise of the system to be less than 0.04 rad(2). In order to show the application of the system towards atomic coherence experiments, we used it to implement electromagnetically induced transparency in a rubidium vapor cell and obtained a reduction in the absorption coefficient of 92%.     

Cover slip external cavity diode laser

A 671 nm diode laser with a mode-hop-free tuning range of 40 GHz is described. This long tuning range is achieved by simultaneously ramping the external cavity length with the laser injection current. The laser output pointing remains fixed, independent of its frequency because of the cover slip cavity design. This system is simple, economical, robust, and easy to use for spectroscopy, as we demonstrate with lithium vapor and lithium atom beam experiments.     

半导体激光器直接电控稳频方法

提出了运用数字控制方法直接控制半导体激光器的结压降来实现稳定半导体激光器输出光频的新方法，推导了原理公式，并给出了实验方案和结果，分析了影响实验结果的因素。     

High resolution self-mixing laser rangefinder

This work describes the development of a novel laser instrument for non-contact absolute distance measurements, working in safety class I. The physical principle of operation is based on the self-mixing effect in a laser diode: the laser diode wavelength is modulated through a change of the supply current, inducing a self-mixing signal. The frequency of the produced fringes depends on the target distance, therefore a particular algorithm is applied, in real-time, to extract the frequency tone of the fringes, even in the case of very low signal-to-noise ratio. The final low-cost instrument is realized with an embedded digital signal processor and works in real-time over diffusive targets, with resolution better than 100 μm for distances up to 2 m.