单频连续染料激光的稳频

本文介绍计量院研制的单频连续染料激光器及其稳频装置。用此装置对自制的和美国S-P公司380A型染料激光器进行稳频,得到激光频率的长期(30分钟)漂移小于1MHz(2×10~(-9)),激光频率的绝对漂移小于30MHz,线宽小于1MHz的结果。此装置可使染料激光频率对准和稳定在5700～6500A波长范围内的任意一条谱线上,也可用于激光分离同位素或高分辨力的激光光谱学中。     

科用外差法测定NH_2D斯塔克盒稳定CO_2激光频率系统的鉴频曲线

本文提出了固定NH_2D分子吸收线型中心频率而改变激光输出频率,用外差拍频计数记录激光频率的变化的外差拍频测定NH_2D Stark盒稳定CO_2激光频率系统中鉴频曲线的方法。利用一支稳频激光器提供参考频率,采用这种方法进行了鉴频曲线的测量。文中给出了实验结果并进行了误差分析。     

计量型紫外显微镜微纳米线宽测量技术的研究

计量型紫外显微镜微纳米线宽测量技术是利用光电倍增管的光电转换效应,将线宽的光学信号转换为电信号,并利用后续信号采样处理电路,提取出线宽的轮廓信号。利用激光干涉仪等精密定位装置,搭建了一套线宽测量系统,对线宽标称值为3 μm的标准样板进行测量,得到的线宽测量值为3.025 μm,与标称值仅相差25 nm。实验表明:该方法可以准确地获取线宽的边界信号,实现线宽的准确测量。     

PTB研发出世界上最小线宽的激光器仅10mHz

<正>激光器是精密的代名词,但一般来说,其还有改进的余地。"完美"的激光器会在一个特定的波长发出一种光。光从激光器中射出,激光起振后,会有一个或多个纵模产生,每个纵模频率的范围就是激光的"线宽"。尽可能缩窄线宽是激光研究的目标之一,现在德国研究人员已经开发出了世界上最小线宽的激光器,线宽仅为     

光频测量用飞秒激光频率梳光谱扩展实验研究

在光频的绝对测量研究中,本研究小组研制了光谱范围为650~950 nm波段、重复频率为350 MHz的"单块"结构钛宝石飞秒激光频率梳。为了实现其对633 nm波长国家副基准频率的绝对测量,本实验分别采用棱镜对和啁啾镜对进行脉宽压缩,然后注入光子晶体光纤进行光谱扩展。实验发现两者均可扩展出短波长方向的光谱,但棱镜对扩谱结构由于具有较长的"光程臂长"容易受到扰动而造成光纤耦合的不稳定,最终表现为光谱中各波长成分的光强不稳定而无法用于光频测量。啁啾镜对结构紧凑、稳定性强,经过脉宽压缩及光子晶体光纤扩谱,最终获得了光谱覆盖600~950 nm波段、各波长成分强度稳定、各光频齿频率稳定度同步于氢原子钟的可用于光频测量的飞秒激光频率梳     

DFB激光器调谐过程的动态线宽特性

为了获取分布反馈(DFB)激光器在调谐过程的动态线宽特性,提出一种基于光纤延时自外差的激光动态线宽测量方法,对于激光器线宽和测量原理做了理论分析.对商品化DFB激光器的实验结果表明:在整个电流工作范围内,激光动态线宽为20.38～4.73 MHz;工作电流为最大电流的0.58～0.66倍时,激光器的动态线宽最窄,激光器动态线宽最佳工作电流为最大电流的0.5～0.8倍.     

Laseranalyzer激光分析仪

本文介绍了激光分析仪的基本测量原理,并介绍了激光分析仪的干扰因素及其针对吸收线宽的变化进行的自动补偿。     

光泵浦XeF(C-A)激光技术研究进展

综述了西北核技术研究所在光泵浦XeF(C-A)激光技术研究方面取得的成果,研制的10 J级激光器最大输出能量为18.7 J,总转换效率达到0.25%,在国际上首次实现了XeF(C-A)激光重频运行,运行频率0.1～1 Hz;描述了光泵浦源的结构和供气装置的研制;介绍了在高重频光泵浦源和激光线宽压缩研究方面的最新进展,光泵浦源最高运行频率达90 Hz,XeF(C-A)激光线宽已被压缩到1nm.     

基于光学锁相环的高稳定度激光稳频方法研究

报道了一种基于光学锁相环的高稳定度激光稳频方法,用于提高可调谐外腔半导体激光器(TECDL)的频率稳定度和准确度。自行研制的光学锁相环电路采用数字鉴相与差分运算相结合的方式获得高灵敏度的鉴频鉴相误差信号,并通过高速模拟PID实现整个系统的闭环锁定。利用该光学锁相环系统进行了TECDL偏频锁定至光学频率梳(OFC)的实验,实验结果表明环路锁定后拍频频率波动在±0.3Hz范围内,偏置频率为50MHz时,光学锁相环系统在1s和1000s积分时间的相对阿伦方差分别为1.5×10^-9和8.5×10^-13。系统锁定后,拍频线宽由500kHz压缩至2kHz。该研究表明采用基于光学锁相环的激光稳频方法可以实现亚Hz级的激光频差控制,通过将TECDL偏频锁定至高稳定度的参考激光源可显著提高其频率稳定度,使其能够满足超精密测量、冷原子/离子干涉测量等领域对激光频率稳定度和准确度的要求。     

赫兹相对线宽的双光梳绝对距离系统

建立了一套基于窄线宽激光相位锁定的双光梳绝对距离测量系统,相对线宽仅为0.35Hz。相较于传统测量方案,这种方法能在大模糊范围内实现快速、高精度的测量。该系统通过结合飞行时间法和干涉测量法的优点,在0.74m的模糊范围内实现了10nm的分辨率,测量时间仅为30ms。通过游标效应可将模糊范围扩展至数公里以上,可满足大部分现场应用需要。     

Frequency Stability of a He-Xe Laser with Nonresonant Feedback

The results of experimental investigation of frequency stability of a He-Xe laser (? = 3.508?) with nonresonant feedback are reported. It is experimentally proved that the mean frequency of oscillations does not depend on the distance between the mirror and the scatterer. It is shown that the spectral width depends on the number N of modes interacting due to scattering. The greater N is, the narrower is the linewidth. In a He-Xe laser with a relatively low number of interacting modes (N = 10) the linewidth is about 15 mHz. The lasers with a large number of interacting modes (N~104 to 106) are considered. The linewidth in such lasers is expected to be 104 to 105Hz. The short-term stability of the laser with nonresonant feedback is determined by the linewidth, but the long-term stability should be much better; it is determined only by the stability of the atomic resonance center.     

Stabilizing the spectrum of a femtosecond Ti:Sapphire laser

A new scheme for stabilizing the beat frequency of the interacting longitudinal modes in a femtosecond Ti:sapphire laser (Femos-1) has been developed and experimentally studied. The stability and frequency spectrum of mode beats in a modified laser have been monitored. A short-term instability of the beat frequency does not exceed 4.8 × 10^?8 (τ = 10 s) over a time scale of 10 min. The laser linewidth in the regime of self-mode-locking is ≤3 Hz at a laser spectrum width of 20 nm.     

Simple method for frequency locking of an extended-cavity diode laser

We have developed an extended-cavity tunable diode laser system that has a small linewidth and a large output power (more than 90% of the free-running power) whose operating frequency can be conveniently locked to a transition line of Rb atoms. Based on flat-mirror feedback and frequency self-locking and with weak feedback, we have achieved a continuous frequency detuning range greater than 900 MHz and a short-time linewidth stability of better than 0.4%. By using a two-step locking procedure we not only can lock the laser frequency but also can detune the frequency to any desired value. The locking is quite sturdy and rugged.     

1.5μm光纤通信波段乙炔稳频激光技术研究进展

1.5μm乙炔饱和吸收谱线是国际计量委员会(CIPM)正式推荐的光纤通信波段复现‘米’定义的频率参考标准。乙炔稳频激光依据稳频方法可分为线性吸收和饱和吸收两大类,饱和吸收相比线性吸收,能够消除乙炔分子的多普勒效应,获得线宽更窄、频率稳定度和复现性更高的稳频激光,1s频率稳定度能够达到10^-13量级,波长漂移为10^-12量级。利用13C2H2(ν1+ν3)P(16)谱线,研发的微型气室有望实现稳频激光的全光纤链路传播,为高度集成化、抗干扰能力强的稳频激光源提供了新的发展方向。高性能的1.5μm近红外稳频激光直接为密集波分复用系统、精密光纤传感等多个领域提供波长参考源,结合飞秒激光频率梳技术可进一步完善光纤通信中激光波长量值传递溯源体系,提升激近红外波段光波长的测量能力,为光纤波段的精密测量提供量值保障。     

Experimental validation of a simple approximation to determine the linewidth of a laser from its frequency noise spectrum

Laser frequency fluctuations can be characterized either comprehensively by the frequency noise spectrum or in a simple but incomplete manner by the laser linewidth. A formal relation exists to calculate the linewidth from the frequency noise spectrum, but it is laborious to apply in practice. We recently proposed a much simpler geometrical approximation applicable to any arbitrary frequency noise spectrum. Here we present an experimental validation of this approximation using laser sources of different spectral characteristics. For each of them, we measured both the frequency noise spectrum to calculate the approximate linewidth and the actual linewidth directly. We observe a very good agreement between the approximate and directly measured linewidths over a broad range of values (from kilohertz to megahertz) and for significantly different laser line shapes.     

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。     

Observation of a Sub-10-Hz Linewidth 88Sr+ 2S1/2–2D5/2 Clock Transition at 674 nm

In this paper, a pair of diode lasers at 674 nm, locked to two independent ultralow-expansion high-finesse cavities, have been characterized by monitoring the beat frequency between them. The individual laser linewidth of 1.4 Hz for a 3-s averaging time broadened to 4 Hz at 30 s. The relative frequency stability of the beat at 1s is 2.5 10^-15. One of the lasers has been used to interrogate the ⁸⁸Sr^{+ 2}Si_1/2-²D _5/2 transition at 674 nm, and a transition linewidth of 9 Hz has been observed     

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.     

Tunable and frequency-stabilized diode laser with a Doppler-free two-photon zeeman lock

We describe frequency locking of a diode laser to a two-photon transition of rubidium using the Zeeman modulation technique. We locked and tuned the laser frequency by modulating and shifting the two-photon transition frequency with ac and dc magnetic fields. We achieved a linewidth of 500 kHz and continuous tunability over 280 MHz with no laser frequency modulation.     

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。