外腔半导体激光器探测1.5μm波段乙炔分子谱线及稳频

用外腔半导体激光器观测到１．５μｍ波段乙炔（Ｃ２Ｈ２）分子１０条吸收谱线，对各谱线中心波长进行准确定标；对１．５３１５９μｍ的吸收线性质做了初步研究。对外腔半导体激光器的频率实现了分子诺线稳频，在１．５３１５９μｍ吸收谱线上，锁定后激光器的频率变化≤±２ＭＨｚ     

半导体激光器谱线展宽因子测量

以１．３μｍＤｈ－ＩｎＧａＡｓＰ半导体激光器为研究对象，利用自发辐射谱测量谱线展宽因子，测出了α因子随工作电流变化的关系曲线。     

一种锁定半导体激光器频率的新方法

报道了一种实现半导体激光器频率锁定的新方法:通过交流磁场对法拉第反常色散光学滤波器(FADOF)的透射谱进行调制,将半导体激光器的频率锁定在FADOF的透射谱上。在B=1.76×10~(-2)T、T=120℃条件下,利用一阶导数稳频技术,测得1s和10s取样时间的频率稳定度分别为1.5×10~(-10)和5.8×10~(-11)。     

半导体激光器稳频综述

在冷原子干涉实验中需要用激光冷却并操控原子,因此对半导体激光器频率的稳定性要求较高。由于半导体激光器本身线宽较大,功率稳定性差,还可能产生慢漂和跳模等现象,故需对半导体激光器进行稳频。本文介绍了饱和吸收谱稳频、波长调制稳频、调制光谱稳频、调制转移光谱稳频、双色激光稳频、频率电压转换稳频6种冷原子干涉实验中常用的稳频方法,分别阐述了各方法的原理、特点、适用领域,为半导体激光器的实际应用提供了参考。     

半导体微腔激光器瞬态特性的分析

建立了反映半导体微腔激光器特性的模型,借助计算机手段,运用Matlab软件直接给出了半导体微腔激光器瞬态响应的仿真结果及载流子密度和光子密度的相图,分析了自发辐射因子、注入电流和腔长对微腔器的激射阈值、延迟时间、驰豫振荡频率和光输出等参量的影响。该模型及有关结合为半导体微胶激光器的工艺制作,改善的高频调制特性和优化器件提供了理论依据。     

全固态激光器的研发与应用概况

半导体激光器泵浦技术为固体激光器注入了新的生机和活力，使全固态激光器同时具有固体激光器和半导体激光器的双重特点，它的出现和逐渐成熟是固体激光器的一场革命，也是固体激光器的发展方向。     

532 nm Nd:YVO4/KTP激光器的I2分子吸收谱线的观测及频率稳定的研究

激光二极管抽运的固体激光器可用于光学计量,长度测量,相干光通信,激光雷达等方面,高精度应用要求激光器的频率稳定。碘分子在５３２ｎｍ附近在上百条强的吸收谱线,采用单频Ｎｄ;ＹＶＯ４／ＫＴＰ激光对碘的一些吸收谱线作了观测,并进行了激光频率稳定的研究,这些吸收谱线是１９９７年９月国际米定义咨询委员会推荐作为频标的９组５３２ｎｍ碘吸收谱线之外的新的参考谱线。     

5GHz主动锁模光纤激光器

在国内首次研制成功半导体激光器泵浦的主动锁模掺饵光纤激光器，器件利用高速ＬｉＮｂＯ３幅度调制器，重复频率达５ＧＨｚ脉宽２４ｐｓ，峰值功率为２．５毫瓦，波长约为１．５５２μｍ。     

自调Q掺饵光纤激光器

研制出一种结构新颖的掺饵光纤激光器，该激光器利用线性光纤环形镜和半导体激光器芯片的背向反射镜组成谐振腔。采用半导体激光器芯片作为饱和吸收体，在９ｍＷ的泵浦功率下，该激光器实现了自调Ｑ脉冲输出。输出光脉冲宽度为１２μｓ，脉冲峰值功率约为２２ｍＷ，脉冲序列的重复周期约为６５μｓ。     

将1500nm InGaAsP BH外腔半导体激光器稳定到氨分子吸收谱线上

基于氨分子在近红外波段振转能级跃迁机制,作者将1500nm GRIN-ROD外腔InGaAsP BH激光器频率锁定到氨(NH_3)分子吸收谱线上,它的波长是1518.2nm。该系统长时间的频率漂移和抖动小于3MHz。     

~85Rb原子D_2线饱和吸收谱稳定半导体激光频率

用780nm AlGaAs半导体激光器和差分放大技术,观测了~(85)Rb原子D_2线(5S_(1/2)-5P_(3/2))B分量(5S_(1/2),F=2→5P_(3/2),F=1,2,3)的消多普勒饱和吸收谱。利用一阶导数和三阶导数稳频技术,实现了对AlGaAs半导体激光的稳频,对于1s和10s的取样时间,频率稳定度可达10~(-10)～10~(-11)。     

Diode-laser frequency stabilization by two-frequency Doppler-broadened absorption spectroscopy

We demonstrate a robust method for frequency stabilization of a diode laser by two Doppler-broadened absorption spectra of the cesium D2 line. This technique employs an acousto-optical modulator to generate another frequency component from a diode laser to perform the spectroscopy. The 852-nm diode laser with frequency stabilization at the zero crossing of the error signal showed a peak-to-peak fluctuation of 800 kHz compared with a frequency-stabilized femtosecond laser over a 2-h period. This frequency-locking method is free of modulation and can be applied to frequency discriminators as well as to atomic resonances.     

法拉第滤光器在法拉第激光器领域研究进展

法拉第激光器是一种利用法拉第反常色散原子滤光器作为选频元件的新型外腔半导体激光器,原理上法拉第激光的输出波长随着激光二极管驱动电流及工作温度的变化,始终与原子跃迁谱线相对应,可以将激光频率有效地锁定至原子跃迁谱线,实现窄线宽的激光输出信号,并且短期与长期频率稳定性均较好。本文详细介绍了自1845年法拉第旋光效应提出以来,法拉第反常色散原子滤光器的发展历程,法拉第激光器的工作机理、发展历程以及性能优越性,并结合国内外的研究进展,介绍了法拉第激光发展各个阶段的技术瓶颈及相应的解决办法,同时展望了法拉第激光器未来在量子领域特别是量子精密测量领域的重要价值。     

High-powered green light generation by intracavity frequency doubling using grating feedback optics

Grating feedback optics is shown to contribute to narrowing the spectral bandwidth of a multilongitudinal-mode laser diode to less than 0.2 nm and tuning the lasing wavelength to the peak absorption wavelength of Nd:YVO(4). A continuous green light of 31 mW was efficiently generated by intracavity frequency doubling of the Nd:YVO(4) laser with a KTiOPO(4) crystal. A relative intensity noise of less than -140 dB/Hz was obtained in the frequency region greater than 2 MHz. The noise characteristics of generated green light are discussed as compared with the case of using a single-longitudinal-mode laser diode as the pumping source.     

Frequency stabilization of a 1.3 microm laser diode using double resonance optical pumping in the 5P 3/2-6S 1/2 transition of Rb atoms

The frequency stabilization of a laser diode in the 1.3 microm region using double resonance optical pumping (DROP) spectrum in the 5P(3/2)-6S(1/2) transition of (87)Rb atoms is demonstrated. The signal-to-noise ratio of the DROP spectrum is approximately ten times higher than that of the previous optical-optical double resonance spectrum. The spectral linewidth of the DROP measures 8.4 MHz. When the frequency of a 1.367 microm laser diode is stabilized to the DROP spectrum, the frequency stability is 9 x 10(-12) after 100 s. Also, the wavelength of the frequency-stabilized laser locked to the 5P(3/2)-6S(1/2) transition using a wavelength meter is measured.     

Spectral and spatial dynamics of a multimode GaN-based blue laser diode

ABSTRACT

High-resolution spectral analysis of a multimode GaN-based blue laser diode was performed as a function of temperature and current both below and above the threshold levels. Maps of longitudinal modes evolution as a function of current and temperature were obtained from the highly resolved emission spectra of the laser diode. The evolution of emitted longitudinal modes with current and temperature exhibited redshifts at rates of 0.0059 nm/mA and 0.0149 nm/°C, respectively. Similarly, the laser gain profile was observed to shift towards longer wavelengths but with rates of 0.022 nm/mA and 0.0439 nm/°C. The longitudinal mode spacing of 0.0540 nm was experimentally evaluated and compared with its equivalent theoretically predicted value.     

Continuous-wave laser spectrometer automatically aligned and continuously tuned from 11.8 to 16.1 microm by use of diode-laser-pumped difference-frequency generation in GaSe

We report a fully automated mid-IR difference-frequency spectrometer with a spectral resolution under 70 MHz pumped by a pair of conventional room-temperature 800-900-nm diode lasers. 0.1 muW of tunable cw radiation is produced from incident-diode powers of 120 and 75 mW. The system has computer-controlled beam alignment with compact CCD cameras, motorized mirrors and positioners to obtain 0.01 degrees crystal-angle positioning, 4-mum beam overlap at the nonlinear crystal, and automated diode laser beam collimation. Computer-operated frequency control uses temperature tuning and current tuning of the free-running diode lasers. The system has been demonstrated by successfully scanning, without any human intervention, 64 randomly selected acetylene absorption lines between 12 and 15 mum. Spectral scans of ammonia are also presented. This mid-IR spectrometer is suitable for fully automated spectroscopy of an unlimited list of mid-IR frequencies and has the potential to detect any trace gas that has an acceptable absorption line within the large tuning range.     

Enhancement of spectral purity of injection-seeded titanium:sapphire laser by cavity locking and stimulated Brillouin scattering

We report improvements to and better characterization of the spectral purity of a diode laser injection-seeded, cavity-locked titanium sapphire laser that serves as the source for a previously reported rubidium vapor spectrally filtered Thomson scattering apparatus at 780.24 nm. In a detailed set of measurements the spectral purity P of the laser, defined as the ratio ofthe narrowband component of the laser output to the total output, has been studied as a function of frequency mismatch between the seed laser frequency and the central frequency of the unseeded cavity. It is found that spectral purity exceeding 0.999 can be obtained for a seed-cavity mismatch as high as +/- 0.25 nm, corresponding to approximately 950 cavity longitudinal-mode spacings and as high as approximately 0.9999 for a cavity-seed mismatch in the range +/- 0.10 nm (380 mode spacings). It is also shown that the addition of an external-cavity stimulated Brillouin-scattering phase-conjugate mirror increases both the spectral purity, to a minimum of 0.99999, and the cavity-seed mismatch range, to +/- 0.25 nm, for which this maximum effective purity is obtained.     

Two-tone frequency-modulation spectroscopy for quantitative measurements of gaseous species: theoretical, numerical, and experimental investigation of line shapes

The capability of retrieving spectral information from line shapes recorded by two-tone frequency-modulation spectroscopy (TTFMS) is investigated. A TTFMS theory accounting for dispersion and nonlinear distortion of diode laser frequency modulation response is presented. The adequacy of the theory for a detailed modeling of line shapes recorded with high resolution is examined. An extensive error analysis of line parameters (i.e., width, intensity, and line center) retrieved by a nonlinear least-squares fitting procedure is made. Plots of residual errors with characteristic signatures that are due to incorrectly assigned modulation parameters and choice of line profile are presented. In least-squares fits to experimental oxygen data with a Voigt profile influence from collisional(Dicke) narrowing is clearly exhibited, and when we used a collisionally narrowed line profile deviations of the model were reduced to less than 0.2%. We demonstrate that accurate quantitative measurements by TTFMS over a wide range of concentrations, temperatures, and pressures are possible.     

Wavelength- and amplitude-modulated photoacoustics: comparison of simulated and measured spectra of higher harmonics

Photoacoustic (PA) spectra generated by current modulation of a distributed feedback diode laser (DFB-DL) were measured for the ammonia absorption line at 1.53 microm and calculated using absorption spectra taken from a database. The algorithm is based on a combined amplitude- and wavelength-modulation (AM-WM) scheme. The spectral characteristics of the DFB-DL were determined by comparing simulated spectra with Fourier transform infrared measurements. PA spectra were measured and simulated from the first to fourth harmonic and a variation of the modulation depth with modulation frequency was observed. It was found that combined AM-WM modulation may produce larger PA signals than separate AM or WM detection for the first harmonic.