双纵模稳频He-Ne激光器工作机理及误差分析

为深入分析双纵模稳频氦氖激光器的稳频机理和精度误差,本文提出了双纵模产生的必要条件:内腔型激光器和谐振腔长在100～300 mm之间.按照激光器的工作过程,稳频分为三个阶段:跳模、过渡阶段,模式稳定.结合激光原理和热力学理论,根据光电探测器的电压变化,阐述了稳频机理.拍频实验结果表明,激光器的频率稳定度高达5×10-10.通过误差分析,确定稳频精度仅取决于腔长的变化量,且增加腔长,有助于增加频率稳定度.该方法锁定时间短.     

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。     

双纵模激光热稳频光源

介绍一种双纵模激光器的稳频装置原理及其电源电路。对稳频机理进行了理论分析，并说明具体调整方法。该光源采用新的热频原理，在普通的全内腔Ｈｅ－Ｎｅ激光器上获得了与塞曼型稳频激光器同一量极的稳频精度，具有成本低，稳频装置简单的特点。     

超导稳频振荡器的研究

基于理论分析和计算机仿真,得到了超导稳频振荡器的设计方案,主要包括高Q超导腔、低温环境及锁相环电路等组件的设计。通过实验验证,超导腔的Q值达到2×10⁹,低温环境温度达到1.8 K,温度的稳定度优于0.001K。根据实验结果优化设计后进行系统联调,得到了初步实验结果,超导稳频振荡器的1s频率稳定度达到10^-13量级     

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。     

偏频锁定0.633μM碘吸收稳频激光

为了满足大尺寸精密干涉测量对干涉信号的信噪比要求，我们研制了偏频锁定氦氖０．６３３μｍ碘吸收稳频激光器，该系统激光的频率不稳定度为５．５×１０－１２（τ＝１０ｓ），系统的频率再现性为４×１０－１１，可连续锁定６个小时以上，无调制输出功率大于０．８ｍＷ。     

精密测频用4mm注入锁相稳频源

本文描述一个用于精密测量亚毫米波频率的4mm注入锁相稳频源,其输出功率约为20mW。当用于精密测量HCN激光器的337μm线时,该稳频源的频率为68.5GHz,最小频率步长为8.1kHz,拍频信号的信噪比不低于150:1。文中还分析了稳频源的短期稳定度。     

镱离子光钟的多波长数字PID激光稳频系统

针对镱离子光钟实验中激光冷却并操控离子时,激光器频率漂移影响原子钟系统的问题,基于数字PID控制方法,设计了一种新的多通道频率-数字信号转换稳频方法,将多路多波长激光频率锁定在波长计的参考频率上。对激光器锁定前和锁定后的频率进行一定时长的数据采集及数据对比,激光频率漂移由800 MHz控制在± 0.8 MHz,激光频率稳定度由9.29 × 10^-10@1 s优化至2.79 × 10^-10@1 s,频率千秒稳达到3.85 × 10^-12。该系统简单、易实现,具有小型化、适应性强的优点。     

全内腔式632.8nmHe—Ne激光器频率稳定的新方法

本文探讨了全内腔式632.8nm He-Ne激光器频率稳定的必要条件,对稳频原理进行了较详细的阐述,提出了检测激光管温度与提取激光输出信号相结合的稳频方法。通过实验获得了满意的结果。     

双闭环兰姆凹陷激光稳频方法

兰姆凹陷稳频激光器环境适应能力较差、在环境温度变化时容易失锁的问题,主要是由于环境温度波动导致的激光器腔长变化超出了压电陶瓷的调整范围。本文提出将兰姆凹陷稳频技术与热稳频技术相结合的方法,利用附加的温度控制系统补偿环境变化造成的激光器管壁温度变化,使工作过程中激光器腔长基本保持稳定,从而保证激光器谐振腔长变化不超出压电陶瓷的补偿范围。试验表明,所用方法解决了兰姆凹陷稳频激光器容易失锁的问题,提高了激光器的环境温度适应性,为兰姆凹陷稳频技术在工业现场的应用创造了条件。     

Frequency stabilization of internal-mirror He-Ne lasers by air cooling

Instead of the traditional heating method, the cavity length of an internal-mirror He-Ne laser is controlled by air cooling which is implemented by a mini cooling fan. The responsive property of the cooling fan and the thermal expansion of the internal-mirror laser tube are investigated. According to these investigations, a controlling system is designed to drive the cooling fan controlling the cavity length of the laser. Then the frequency is stabilized by comparing the light intensities of two operating longitudinal modes. The results of beating with an iodine stabilized He-Ne laser show that a relative uncertainty (Δf/f-) of 4.3×10^-9 in 5 months, a frequency fluctuation of <1.4 MHz, and an Allan deviation of 6×10^-11 (τ=10,000 s) in 20?h are obtained.     

The influence of Ne isotopes on the single mode operation of He-Neand He-Ne/I2 lasers

When using He-Ne lasers in our experiments, we observed that two adjacent longitudinal modes with the same polarization operate simultaneously with steady output power for each mode when the frequency spacing between them is several times lower than the homogeneous linewidth of the laser transition. In the case of a mixture of ²⁰ Ne and ²²Ne isotopes, an analytical expression for the output power is obtained and calculated for parameters close to the experimental conditions. The theoretical predictions are in agreement with the experimental results. The theory also shows that in the case of pure neon isotope the competition between the longitudinal modes is stronger than in the case of neon isotopes mixture. It is proposed to improve the single mode selection efficiency for He-Ne and He-Ne/I₂ lasers and to enhance their single-mode output power using pure neon isotopes     

Three-longitudinal-mode He-Ne laser frequency stabilized at 633 nm by thermal phase locking of the secondary beat frequency

We present a simple scheme for thermal frequency stabilization of a three-longitudinal-mode He-Ne laser at 633 nm with improved short-term (5 x 10(-11) at 1-s average time) and long-term (124-kHz standard deviation for 10 h) frequency stability. A stabilized output power of 3 mW was readily obtained from the central mode by polarization-mode selection. The optical frequency of the central mode could be precisely tuned by an external frequency reference over 160 MHz with high precision or could be optically phase locked to a reference laser by use of a thermal frequency-stabilization circuit and an external acousto-optic modulator. The laser will be useful in various applications for which a laser source with high power and frequency stability is necessary.     

Frequency Stability Improvement of a Two-Mode Stabilized 633-nm He-Ne Laser

The red side (lower-frequency) mode of a two-mode stabilized 633-nm He-Ne laser has been locked to the hyperfine structure of the P() line of (127)I(2) by means of frequency modulation spectroscopy enhanced by an external optical cavity. Both the red side and blue side (higher-frequency) modes of the laser exhibit a frequency stability of 2.3 x 10(-11) tau(-1/2). In addition, the frequency fluctuations of the blue side mode are detected by a Fabry-Perot cavity and compensated through an acousto-optic frequency shifter. The short-term stability of better than 3 x 10(-11) is attained for integration times of between 2 x 10(-3) and 2 x 10(-1) s.     

Flight qualification of a diode laser for path difference determination of a high-resolution fourier transform spectrometer

Diode lasers offer a lightweight, rugged, and economic alternative to other types of laser source, but they often do not provide long-term stability and spectral purity of emission. We have developed a stabilized, near-infrared diode laser source that is capable of as much as 20 mW of single-mode output power for the effective replacement of a He-Ne laser in the path difference measuring system of a high-resolution (1.25-m maximum path difference) Fourier transform spectrometer. Laser characterization has been performed both in laboratory measurements and in flight tests, resulting in a relative frequency stability of better than 10(-6) on a 6-h flight.     

A heterodyne laser system to study frequency stabilized Zeeman 633 nm He-Ne lasers deficient in temperature steadiness

A heterodyne laser system is constructed to study the effect of external transverse magnetic field on the dynamic instability of internal mirror TEM_00q He-Ne lasers having temperature instability. The system could provide precise detailed knowledge about the roles of both the temperature and the applied magnetic field separately. Two different internal mirror 633 nm TEM_00q He-Ne lasers with frequency stability of 10⁻⁶ are studied. The applied transverse magnetic field on He-Ne lasers increased the frequency stability to be in the order of ∼10⁻¹⁰, in spite of temperature instability. In the same time, a single-mode operation with an enhanced laser output power is obtained. The sensitivity of the method showed that the laser exhibits a short-term frequency stability of 4.7×10⁻¹⁰, which after one minute, when mode collapse starts, decreased to 2.6×10⁻⁸, over the next four minutes. This increase in the frequency difference of the inter-mode beat signal that affect the stability is attributed to the uncontrolled temperature of the laser tube. The results revealed that the magnetic field plays the dominant role to achieve the maximum frequency stability, while the unsteadiness of temperature of the laser tubes limits the long term single-mode laser operation.     

Frequency shifts of iodine stabilized He-Ne lasers at higherharmonic order stabilization

The frequency shifts of an ¹²⁷I₂ stabilized He-Ne laser at 633 nm have been measured at the third, fifth, and seventh harmonic stabilization using a digital signal processing lock-in amplifier. The observed frequency shifts confirmed the previous theoretical prediction that the laser frequency depends on the harmonic order of stabilization. The lower effects of modulation amplitude shift, power shift, and iodine pressure shift at the fifth harmonic stabilization indicate a potential improvement of the frequency reproducibility of the laser standard. A model is suggested to describe the power shifts of the laser. The mechanism explains the lower power shift of some lasers when they are operated at relatively high intracavity power