基于飞秒光频梳的双频He-Ne激光器频率测量

利用光纤飞秒光频梳和外腔可调谐半导体激光器, 建立了一套双频He-Ne激光器频率测量系统. 选用铷钟作为系统的频率基准, 通过将外腔半导体激光锁定至光频梳使得其频率溯源至铷钟, 再利用外腔可调谐半导体激光与双频He-Ne激光器输出的正交偏振激光拍频, 同时测量两路正交偏振激光频率. 将可调谐半导体激光器锁定至光频梳第1894449个梳齿, 其绝对频率为473612190000.0±2.7 kHz, 相对不确定度为5.7×10^-12. 对商品双频He-Ne激光器进行频率测量实验, 双频He-Ne激光器水平方向偏振激光频率均值为473612229934 kHz, 竖直方向偏振激光频率均值为473612232111 kHz, 平均时间为1024 s的相对Allan标准差为5.2×10^-11, 频差均值为2.177 MHz, 标准偏差为2 kHz.     

基于飞秒光频梳的压电陶瓷闭环位移控制系统

利用飞秒光频梳、外腔可调谐半导体激光器和法布里-珀罗干涉仪建立了一套压电陶瓷亚纳米级闭环位移控制系统. 将可调谐半导体激光器锁定至光频梳, 通过精确调谐光频梳的重复频率, 实现了半导体激光器在其工作频率范围内的精密调谐. 利用Pound-Drever-Hall锁定技术将带有压电陶瓷的法布里-珀罗腔锁定至半导体激光器, 进而通过频率发生系统控制压电陶瓷产生亚纳米级分辨率的位移. 实验研究发现锁定至光频梳后可调谐半导体激光器1 s的Allan标准偏差为1.68×10^-12, 将其在30.9496 GHz范围内进行连续闭环调谐, 可获得压电陶瓷的位移行程约为4.8 μm; 以3.75 Hz的步长扫描光频梳的重复频率, 实现了压电陶瓷的450 pm闭环位移分辨率并测定了压电陶瓷的磁滞特性曲线. 该系统不存在非线性测量误差, 且激光频率及压电陶瓷位移均溯源至铷钟频率源. 关键词： 光频梳 压电陶瓷 法布里-珀罗腔 可调谐半导体激光器     

光纤飞秒光学频率梳的研制及绝对光学频率测量

实验利用商品光纤飞秒激光器,自行构建了一套完整的光学频率梳系统,并获得了约30 dB信噪比的系统频移(f_ceo)信号.实现了光频梳重复频率(f_rep)信号及系统频移(f_ceo)信号的高稳定度锁定,并通过实验验证了光频梳锁定的跟踪精度.基于此稳定光频梳完成了对1064 nm碘稳频Nd:YAG固体激光器的绝对频率测量.实验结果表明,f_rep的跟踪精度在100 s取样时间时优于3.7×10^-14,测量得到的1064 nm激光器绝对频率为:281630111757362 Hz.这一测量结果与国际计量委员会(CIPM)给出的国际推荐值符合到不确定度之内. 关键词： 光纤光频梳 稳频 锁相技术 光学频率计量     

飞秒光梳和碘稳频532nm Nd:YAG激光频率的测量

报道了中国计量科学研究院研制的基于掺钛蓝宝石(Ti:Sapphire)锁模飞秒脉冲激光器的飞秒光学频率梳装置，并利用此装置测量了碘稳频532nm(¹²⁷I₂R(56)32-10) Nd∶YAG固体激光器的频率，结果为 563260223512991±20Hz,相对不确定度为3.6×10^-14.这一数值是直接溯源到铯原子微波频率基准的光学频率测量结果.     

飞秒钛宝石光学频率梳的精密锁定

经相位锁定后的飞秒钛宝石光学频率梳已经广泛用于绝对光频的测量，这是光频标领域一个革命性的突破.在自建的90MHz飞秒钛宝石激光器的基础上首先采用光子晶体光纤将其光谱展宽到一个光倍频程，接着利用锁相环技术分别将重复频率和载波包络频移同时高精度地锁定到一台稳定度为6×10^－14的Cs钟上，进而得到了稳定度相同的飞秒光学频率梳.     

台阶高度测量方法研究现状及进展

台阶高度测量是目前新提出的国际计量比对项目之一,当前的趋势是向纳米量级精度发展并尽量扩大测量范围。在分析现状和背景的基础上,大致归类了测量台阶高度的几种光学方法,着重介绍了其中绝对干涉方案的最新进展,从测量原理、测量精度以及量程等几方面比较了它们的优缺点。在此基础上提出以可调谐半导体激光器作为光源,采用可调合成波长链法实现纳米级精度毫米级量程的台阶高度测量,详细分析了方案的原理误差,得到最后的结论。     

双路光谱展宽的钛宝石飞秒光学频率梳系统

对中国计量科学研究院研制的第一代基于钛宝石飞秒激光器的光学频率梳系统进行了改进和优化. 通过对激光器重复频率、光谱展宽以及拍频信号探测等方面的改进,有效地降低了光谱展宽的复杂性,提高了飞秒光学频率梳系统的稳定性和激光频率测量的便捷性. 采用该光学频率梳系统对碘稳频532 nm和碘稳频633 nm激光绝对频率进行了测量,测量结果在国际推荐值的不确定度范围之内. 关键词： 光学频率计量 飞秒光学频率梳 光谱展宽     

频率可调谐光栅反馈式扩展腔二极管激光器的搭建与测试

采用Littrow结构,用半导体激光器加上光栅反馈组成外腔可调谐半导体激光器.利用光栅的1级衍射光,反射至激光管选择激光频率,获得红光或近红外波长的单纵模、窄带宽、连续可调谐的激光输出.光栅平面同时作为激光外谐振腔的一个端面,外腔的模式选择、光栅选频作用,以及激光管本身的模式选择(内腔模式)的共同作用,最终产生可调谐的单纵模激光输出.     

基于石英音叉增强型光谱技术(QEPAS)的实时探测系统研究

利用石英音叉增强型光谱技术(QEPAS)结合基于Lab-VIEW设计的数字 频率锁定技术建立了一套气体实时探测系统, 该方案使用3f信号作为误差反馈信号, 将激光器锁定在待测气体吸收峰的中心位置, 保证了长时间测量的准确度并且提高了探测效率. 实验中采用中心波长位于1.396 μm的DFB半导体激光器作为光源, 选择常压下空气中的水汽作为研究对象, 对系统性能进行了测试, 并对影响影响系统探测灵敏度的主要因素进行了分析. 实验结果表明, 该系统可以将激光器稳定在± 0.001 cm^-1范围内, 对激光器长时间工作时的波长漂移起到了很好的抑制作用, 系统的检测限约为1 ppm, 该方案可以直接应用于工业气监测、痕量污染物实时测量等领域.     

光梳主动滤波放大实现锶原子光钟二级冷却光源

提出一种结合注入锁定技术的主动滤波放大方法,将光梳直接注入锁定至光栅外腔半导体激光器,产生窄线宽激光光源,该光源可以用于锶原子光钟二级冷却.实验中,将中心波长为689 nm,带宽为10 nm的光梳种子光源注入689 nm光栅式外腔半导体激光器,通过半导体增益光谱与半导体光栅外腔,从飞秒光梳的多个纵模梳齿中挑选出一个纵模模式来进行增益放大,再通过模式竞争,实现单纵模连续光输出;同时,光梳的重复频率锁定在线宽为赫兹量级的698 nm超稳激光光源上,因此,注入锁定后输出的窄线宽激光也继承了超稳激光光源的光谱特性.利用得到的输出功率为12 mW的689 nm窄线宽激光光源实现了88Sr原子光钟的二级冷却过程,最终获得温度为3μK,原子数约为5×10~6的冷原子团.该方法可拓展至原子光钟其他光源的获得,从而实现原子光钟的集成化和小型化.     

Frequency-comb-referenced two-wavelength source for absolute distance measurement

We propose a new tunable laser source concept for multiple-wavelength interferometry, offering an unprecedented large choice of synthetic wavelengths with a relative uncertainty better than 10(-11) in vacuum. Two lasers are frequency stabilized over a wide range of frequency intervals defined by the frequency comb generated by a mode-locked fiber laser. In addition, we present experimental results demonstrating the generation of a 90 mum synthetic wavelength calibrated with an accuracy better than 0.2 parts in 10(6). With this synthetic wavelength we can resolve one optical wavelength, which opens the way to absolute distance measurement with nanometer accuracy.     

Frequency comb-referenced narrow line width diode laser system for coherent molecular spectroscopy

We analyze in detail the frequency noise properties of a grating enhanced external cavity diode laser (GEECDL). This system merges two diode laser concepts, the grating stabilized diode laser and the diode laser with resonant optical feedback, thus combining a large tuning range with an excellent short-term frequency stability. We compare the frequency noise spectrum of a GEECDL to that of a grating stabilized diode laser and demonstrate a 10-fold reduction of the frequency noise linear spectral density. The GEECDL is phase locked to a similar laser and to a fs-frequency comb with a servo loop providing an open-loop unity-gain frequency of only 237 kHz, which is a tenth of the bandwidth typically required for grating stabilized diode lasers. We achieve a residual rms phase error as small as 72 mrad (≈ 200 mrad) for stabilization to a similar laser (to the fs-frequency comb). We demonstrate that the novel diode laser can phase-coherently track a stable optical reference with an instability of 1.8×10^-16 at 1 s. This laser system is well suited for applications that require phase locking to a low-power optical reference under noisy conditions. It may also be considered for the implementation of optical clock lasers. PACS 42.55.Px; 42.60.Jf; 42.50.Gy     

一种新型可调谐锁模光纤激光器

利用法布里-珀罗腔的激光二极管作为调制器件，实现环形腔光纤激光器的主动锁模。并利用法布里-珀罗腔的激光二极管的多纵模特性，把激光二极管当作一梳状滤波器，通过偏振控制器来调整入射到激光二极管内光的偏振态，同时均衡腔内增益，得到波长大范围可调谐的锁模激光，其脉冲宽度约为48ps，脉冲重复速率2GHz。     

Generation of phase-locked and tunable continuous-wave radiation in the terahertz regime

Broadly tunable phase-stable single-frequency terahertz radiation is generated with an optical heterodyne photomixer. The photomixer is excited by two near-infrared CW diode lasers that are phase locked to the stabilized optical frequency comb of a femtosecond titanium:sapphire laser. The terahertz radiation emitted by the photomixer is downconverted into RF frequencies with a waveguide harmonic mixer and measurement-limited linewidths at the Hertz level are demonstrated.     

Optical amplifier for femtosecond frequency comb measurements near 633 nm

An optical amplifier operating at the 633-nm wavelength region is designed for absolute frequency measurements of iodine-stabilized He-Ne lasers with an optical femtosecond frequency comb generator. The same setup can also be used in other applications that require relatively high (15 mW) laser powers with good spectral characteristics. Radiation of a master laser is amplified by a microlens-coupled diode laser, which is injection locked to the frequency of the master laser. The amplifier can be reliably operated over several hours with very low phase noise. Optical amplification of more than 39 dB is demonstrated. PACS 06.20.Fn; 06.30.Ft; 42.55.Px; 42.62.Eh     

Study of the thermal stability of Zerodur glass ceramics suitable for a scanning probe microscope frame

The work presents measurements of the length stability of Zerodur glass ceramic with temperature change. Measurement of this thermal characteristic is necessary for determination of the optimal temperature at which the Zerodur glass ceramic has a coefficient of thermal expansion close to zero. The principle of the measurement is to monitor the length changes using an optical resonator with a cavity mirror spacer made from the Zerodur material to be studied. The resonator is placed inside a vacuum chamber with a temperature control. A tunable laser diode is locked to a certain optical mode of the resonator to monitor the optical frequency of this mode. A beat-note signal from optical mixing between the laser and a stabilized femtosecond frequency comb is detected and processed. The temperature dependence of the glass ceramics was determined and analyzed. The resolution of the length measurement of the experimental set-up is on the order of 0.1 nm.