Precise wavelength control of a single-frequency pulsed Ho:Tm:YLF laser

We demonstrate wavelength control of a single-frequency diode-pumped Ho:Tm:YLF laser by referencing its wavelength to an absorption line of carbon dioxide. We accomplish this wavelength control by injection seeding with a cw Ho:Tm:YLF laser that can be tuned over or stabilized to carbon dioxide or water vapor lines. We show that the pulsed laser can be scanned precisely over an absorption line of carbon dioxide by scanning the injection seed laser wavelength. We locked the pulsed laser to within 18.5 MHz of the absorption line center by stabilizing the injection seed on the line center. The single-frequency pulsed output, intended for use as a transmitter for differential absorption lidar detection of atmospheric carbon dioxide and water vapor and for coherent detection of wind, is 100 mJ per pulse at a 5-Hz repetition rate.     

Modeling of Tm, Ho:YAG and Tm, Ho:YLF 2- mum Lasers and Calculation of Extractable Energies

The development of a model for 2-mum laser operation in Tm, Ho:YAG and YLF crystals pumped in the near infrared is reported. This model, based on a simplified spectroscopic scheme, is fitted to a set of characterization experiments by means of three adjustable parameters. Results show that the excited-state populations are predicted with a relative accuracy of approximately 10% for a large range of pump levels. Using this model, we calculate the extractable energy on short-laser-pulse interactions for the two materials under different operation conditions. We study the sensitivity to pump duration and the optimization of dopant concentrations. We investigate the improvement of the extractable-energy efficiency with multiple-pulse operation. For double-pulse operation the improvement is approximately a factor of 1.5 and leads to overall extractable-energy efficiencies of 16% in YAG and 15% in YLF for an absorbed pump energy of 10 J cm(-3).     

Flash-lamp-pumped Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF lasers: modeling of a single, long pulse length comparison

Two methods of producing the long pulse lengths that promote efficient extraction of energy from low-gain, quasi-four-level lasers are analyzed. A long pulse length output can mitigate laser-induced damage effects and can be generated in quasi-four-level lasers by two disparate methods. One method utilizes Q-switching techniques in resonators designed to extend the pulse length and another utilizes the first pulse in a relaxation oscillation pulse train. Models for quasi-four-level lasers are derived here taking into account the nonnegligible thermal population of the lower laser level. Closed-form expressions are derived for both modes of operation of quasi-four-level laser systems so the parametric dependencies of both forms of operation become obvious, allowing facile comparison. In addition, a combined absorption and quantum efficiency, germane for flash-lamp pumping, is calculated for both Cr and Er sensitizers. Although the former has the advantage of broad absorption bands, the latter has the advantage of a quantum efficiency approaching 3.     

Flash-lamp-pumped Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF lasers: experimental results of a single, long pulse length comparison

Flash-lamp-pumped, room-temperature Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF are compared for single but long pulse operation, with pulse lengths of approximately 1.0 mus. Under similar operating conditions in normal-mode operation, a slope efficiency of 0.0331 was observed for Ho:Tm:Er:YLF compared with 0.0047 for Ho:Tm:Cr:YAG. For Q-switched operation, Ho:Tm:Er:YLF yielded a slope efficiency of 0.0075. In comparison, a slope efficiency of 0.0012 was obtained for Ho:Tm:Cr:YAG. Two methods of producing long pulse lengths are compared: pulse selection of normal-mode relaxation oscillations and Q-switching in a long resonator. Theoretical models developed in a companion paper for normal-mode relaxation oscillations and Q-switching in quasi-four-level solid-state lasers are in agreement with the experimental results.     

Numerical study of passive Q switching of a Tm:YAG laser with a Ho:YLF solid-state saturable absorber

In a previous work [Appl. Phys. Lett. 65, 3060 (1994)] we experimentally demonstrated that passive Q switching of a 2,017-nm, flashlamp-pumped Tm,Cr:YAG laser with a Ho:YLF saturable absorber could be obtained with an internal focusing lens. We numerically investigate the optical performance of the Ho:YLF Q-switched Tm:YAG laser system by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with those obtained experimentally. With typical laser configuration, a Q-switched laser pulse of 35 mJ in 30 ns is obtained.     

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。     

Comparison of Lasing Performance of Tm, Ho:YLF Lasers by use of Single and Double Cavities

The lasing performance of single-cavity and double-cavity Tm, Ho:YLF lasers was measured experimentally. The maximum, single-longitudinal mode output power for the double-cavity laser was 30 mW, whereas for the single-cavity laser it was 7 mW. We determined the frequency stabilities to be 600 Hz for a single-cavity laser and 300 Hz for a double-cavity laser, by measuring the fluctuation of a self-heterodyne beat signal for a 1.5-micros delay time over a 10-min integrated period. In addition, we obtained a 15-GHz frequency tuning range for the double-cavity laser by changing its cavity length under maximum stable conditions at room temperature.     

Frequency Stabilization of a Diode Laser at 1540 nm by Locking to Sub-Doppler Lines of Potassium at 770 nm

An external cavity 1540-nm diode laser was frequency doubled in a 3-cm-long periodically poled LiNbO(3) waveguide doubler with 150% W(-1) conversion efficiency, thereby generating more than 3 muW at 770 nm. Second-harmonic light was used to detect and lock to sub-Doppler lines of the (39)K D(1) transition.     

1.5μm波长DFB半导体激光乙炔（^12C2H2）线性吸收稳频

建立1．5μm波长标准的工作既是现实应用的需求,也将填补波长计量标准系列在近红外波段的空白。本报导中国计量科学研究院在这项研究中的第一阶段工作：用国产分布反馈半导体激光（DFB－LD）和自行研制的乙炔（^12C2H2)吸收室,进行了吸收光谱实验,实现了1．5μm BFB-LD的C2H2线性吸收稳频。并对实验结果进行初步分析和提出了下一步工作的设想。     

Absorption Bands of Carbon Dioxide From 5.3 to 4.6 Microns

Measurements have been made of the frequencies of the infrared absorption lines of CO₂ in the region from 1850 cm⁻¹ to 2150 cm⁻¹. Observations were made at various pressures and pathlengths up to a maximum of 72 meter-atmospheres. Vibration-rotation constants were obtained characterizing the transitions 11^1c0–000, 11^1d0–000, 03^1c0–000, 03^1d0–000, 200–01^1c0, I2^2c0–01^1c0, 12^2d0–01^1d0 for C¹²O₂. The 11^1c0–000 band due to the C¹³O₂ molecule was also measured.     

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。     

Growth of YLF:Yb:Tm:Nd for optical applications

The focus of this study is the behavior of Tm, Yb and Nd ions in the LiYF₄ (YLF) crystal. One YLF crystal was successfully grown by the Czochralski method; it was doped with 20 mol% Yb, 1.3 mol% Nd and 0.05 mol% Tm. The segregation coefficients of the dopants and lattice parameters were determined. The spectroscopic properties of samples with different amounts of Nd were obtained from absorption and emission studies.     

~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)。     

基于多次反射直接吸收精确测量二氧化碳浓度的研究

二氧化碳气体排放过多是造成温室效应的主要原因,对全球环境及生态系统产生了深远影响。企业燃料燃烧产生的二氧化碳是城市区域碳排放的主要来源。为了通过碳排放交易来实现企业减排,就必须对企业烟囱排放二氧化碳进行精确的计量,而企业烟囱排放的二氧化碳含量一般在20%以下,需要建立高准确度的现场测量方法。通过多次反射吸收光谱技术精确获得二氧化碳在6 361. 25 cm^-1的(30012)←(00001) R18e跃迁谱线信息,进一步结合理想气体方程来精确获得15%,10%,5%和1%二氧化碳/氮气(氮气为平衡气体)混合物的浓度。结果表明所建立的装置和方法能够快速精确地测量待测气体的浓度,测量结果与基于天平的称重法相当,扩展相对不确定度小于0. 65%(k=2)。     

激光稳频技术在大气探测激光雷达中的应用研究进展

大气探测激光雷达因其时空分辨率高、探测精度高等特点,在大气探测、环境监测、国防安全等研究领域应用广泛。根据大气探测激光雷达的测量原理,其光源的频率稳定性会对大气参数的测量和反演产生巨大影响,因此,对光源进行稳频尤为重要。综述了目前应用于大气探测激光雷达的4种激光稳频技术及特点,介绍了这些稳频技术在大气探测激光雷达中的应用研究现状,为未来研制高精度大气探测激光雷达提供参考和借鉴。     

Theoretical modeling and design of a Tm, Ho:YLiF4 microchip laser

We present theoretical modeling that makes it possible to compute the output characteristics of a laser-pumped codoped Tm, Ho microchip laser and the experimental results already obtained with a Tm, Ho:YLiF(4) crystal. By taking into account the match of the pump beam to the self-induced eigenmode of the cavity, we find good agreement between theory and experiment when the pump beam size is properly adjusted relative to the absorbed pump power and the crystal characteristics.     

半导体激光器用铷D2线光电流谱稳频

本文报导了用铷原子７８００Ａ光电流谱来稳定半导体激光器的工作，在光电流谱线的中部发现了有利于稳频的凹陷，将半导体激光器频率锁定在凹陷的中央，估算的频率稳定度为１ＭＨｚ。     

Double-Pass-Pumped Tm:YAG Laser with a Simple Cavity Configuration

For a double-pass-pumped cw Tm:YAG laser, we developed a theoretical model, taking into account reabsorption loss and mode matching between the pumping light and the cavity mode. We also demonstrated that efficient operation can be obtained with a simple cavity configuration by using a dichroic output mirror, highly reflective at the pumping wavelength and partially reflective at the lasing wavelength. Experimental comparisons of this pumping method with single-pass pumping showed that the longitudinally double-pass-pumped Tm:YAG laser performs as well at room temperature as the single-pass-pumped laser performs at -10 degrees C.     

Tunable Continuous-Wave Yb:YLF Laser Operation with a Diode-Pumped Chirped-Pulse Amplification System

We have demonstrated a diode-pumped Yb:LiYF(4) (Yb:YLF) laser oscillator for the first time to our knowledge. A wide tuning range of 25 nm and a high slope efficiency of 50% were obtained at a high laser-diode pump intensity of 100 kW/cm(2). Emission and absorption spectra of the Yb:YLF crystal at 8 K represent a wide laser gain width of 38 nm, indicating efficient laser operation similar to that of a four-level laser system with a reduced saturation fluence of 11 J/cm(2).