F-P半导体激光器实现多波长注入锁定

F-P半导体激光器中对于TE模比TM模有更大的束缚系数,并且在其反射面上有更高的反射率.当TE模和TM模同时注入F-P半导体激光器的谐振腔时,TE模方向的信号得到增长,TM模方向的信号受到抑制.F-P半导体激光器的这种特性使得它类似于一个偏振器,但是其优越之处在于经过F-P半导体激光器注入锁定之后的光信号没有功率损耗.采用F-P半导体激光器的注入锁定原理,使入射光信号没有功率损耗地由偏振光转换为部分偏振光,降低了通信系统中传输信号的偏振敏感性,使传输信号的质量得到提高,实现了F-P半导体激光器三波长和四波长注入锁定.     

Dispersion measurement technique based on the self-seeding laser oscillation of a Fabry-Perot laser diode

A simple dispersion measurement technique has been proposed and demonstrated by using the self-seeding laser oscillation of a Fabry-Perot laser diode through an optical closed-loop path. When the multi-mode optical pulses emitted from the laser are re-injected into the laser after traversing a fiber-under-test, a single mode laser oscillation occurs through the closed-loop path due to the group velocity difference between the pulses of different wavelengths. We measured the dispersion parameter of the fiber-under-test from the modulation frequency changes required to induce single-mode laser oscillations through the optical closed-loop path. The maximum measurement error was less than 1.5% for the optical fibers as compared with a commercial instrument.     

Demonstration of a passive subpicostrain fiber strain sensor

We demonstrate a fiber Fabry-Perot (FFP) sensor that is capable of detecting subpicostrain signals, from 100 Hz and extending beyond 100 kHz, using the Pound-Drever-Hall (PDH) frequency locking technique. A low-power diode laser at 1550 nm is locked to a free-space reference cavity to suppress its free-running frequency noise, thereby stabilizing the laser. The stabilized laser is then used to interrogate a FFP sensor whose PDH error signal yields the instantaneous fiber strain.     

Tunable single-mode Fabry-Perot laser diode using a built-in external cavity and its modulation characteristics

A tunable single-mode laser is obtained by using a weakly coupled cavity structure involved in a coaxially packaged Fabry-Perot laser diode. The cleaved end facet of the coupling fiber becomes an optical reflector and forms an external cavity with a laser facet. The single-mode oscillation condition is controlled and stabilized by tuning the operating temperature. The tuning range is about 10 nm with the side-mode suppression ratio of more than 27 dB when the temperature changes from 11.5 degrees C to 25 degrees C. Direct modulation characteristics were investigated, and our results show that a shorter external cavity can bear deeper modulation depth.     

Heterodyne mixing of two far-infrared quantum cascade lasers by use of a point-contact Schottky diode

We demonstrate heterodyne mixing of two free-running, multimode, 3.3-THz quantum cascade lasers by use of a point-contact Schottky diode. By temperature tuning the emission wavelength of one laser, a difference frequency signal spanning the 2-4-GHz range is obtained, with a signal-to-noise ratio of 30 dB. The frequency of the heterodyne signal is subject to random fluctuations of a few megahertz, principally from instabilities in the temperatures of the devices. From single-shot measurements we derive an instantaneous linewidth for a single Fabry-Perot mode of 20 kHz, corresponding to an integration time of 3.6 ms.     

利用可调谐激光吸收光谱技术对光路上气体温度分布的测量

利用可调谐激光吸收光谱技术(TDLAS),扫描多条吸收谱线以实现气体温度分布的测量。文章给出了温度分布测量的原理和方程离散化的方法,在气体浓度和压力均匀时,利用带约束最小二乘法计算得到温度分布。根据HITRAN中6 330 cm-1附近的4条CO谱线的参数,建立了温度在300和600 K时,路径长度均为55 cm的两段温度分布模型,模拟了测量误差与温度区间长度约束条件的影响。结果表明随着测量误差的增大和约束条件的减弱,计算结果误差相应增大。在5％的测量误差下,计算结果的最大误差为11％,平均误差为2.2％。以管式炉中的高温段和室温下的低温段作为两段温度分布模型进行试验。利用6 330 cm-1处的垂直腔面发射激光二极管(VCSEL)扫描得到的4条CO谱线,通过背景信号的三次多项式拟合得到基线,求出温度分布计算所需的光谱吸收率积分值。在四种情况下, 计算温度分布结果与模型误差分别为7.3％,6.5％,4.7％和2.7％。     

Single-shot distributed optical-fiber temperature sensing by the frequency-derived technique

We present, for the first time to our knowledge, a distributed optical-fiber temperature sensor, based on a pulsed laser, that provides distributed temperature measurement by use of a single pulse propagating in an optical fiber. The system uses the frequency-derived technique based on the optical Kerr effect. The performance of the system is investigated for the temperature range 33-150 degrees C. A linear relationship between the temperature and the derived frequency is obtained. The best temperature resolution was determined to be +/-1.2 degrees C. The best measured spatial resolution was 0.56 m.     

Double sinusoidal phase modulating laser diode interferometer for thickness measurements of transparent plates

A double sinusoidal phase modulating (SPM) laser diode interferometer for thickness measurements of a transparent plate is presented. A carrier signal is given to the interference signal by using a piezoelectric transducer, and the SPM interferometry is applied to measure the thickness of a transparent plate. By combining the double-modulation technique with the Bessel function ratio method, the measurement error originating from light intensity fluctuations caused by the modulation current can be decreased greatly.The thicknesses of a glass parallel plate and a quartz glass are measured in real time, and the corresponding experimental results are also given.     

Mutual injection locking of an erbium-doped fiber laser and a fiber-pigtailed Fabry-Perot laser diode

Mutual injection locking of a fiber-pigtailed Fabry-Perot laser diode (FPLD) and a closed-loop erbium-doped fiber-amplifier-based laser (EDFL) system are studied. A single FPLD longitudinal mode can be lasing in the EDFL-FPLD link, with a reduced linewidth of <0.017 nm and an improved sidemode-suppressing ratio of 50 dB. The FPLD's optimized current range is below threshold within 10%, and its required feedback-injecting power is 12.4 microW (corresponding to 0.03% of the EDFL output power). The maximum detuning ranges of the current and temperature of the FPLD that preserve the narrow linewidth and the highest sidemode-suppressing ratio of the EDFL-FPLD link are 2.4 mA and 2.2 degrees C, respectively. The power dissipated by the EDFL-FPLD link is 20% more than that of the free-running EDFL.     

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     

Room temperature single-frequency output at 2118 nm from a diode-pumped Tm,Ho:YAP laser

A diode end-pumped single-frequency Tm, Ho:YAP laser at room temperature was reported. We demonstrated a single-frequency Tm, Ho:YAP laser at 2118.09 nm wavelength with output power up to 57 mW using two Fabry-Perot intracavity etalons. The optical conversion efficiency is 2.0% and the slope efficiency is 12.7%. The measured full width at half maximum linewidth was <7.5 pm limited by the resolution of the scanning Fabry-Perot etalon used to make the measurement. The wavelength was demonstrated to be stable to about 2 pm over 40 s time periods limited by the temperature stability of the laser. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.     

基于有源Fabry-Perot腔的激光脉冲延时自外差研究

对注入有源Fabry-Perot腔内的单纵模脉冲进行了延时理论分析, 计算了Fabry-Perot腔内增益, 并对脉冲输出进行了数值模拟, 结果表明当脉冲能量衰减到一定值时, 新增抽运粒子数提供的增益可以补偿腔内损耗, 延时脉冲的输出可以达到稳态. 然后利用激光二极管侧面抽运Nd: YAG激光器做为Fabry-Perot腔, 对外部入射的单纵模脉冲光进行了延时, 得到了延时时间2 μups、脉冲数量140个的实验结果. 最后利用有源Fabry-Perot腔对参考光进行延时, 声光移频器对信号光产生频移, 进行了外差实验, 实验结果与移频器的设置值相符, 误差在4%以内.     

基于时分复用技术的吸收光谱气体温度在线测量研究

可调谐半导体激光吸收光谱技术是一种具有高灵敏度、高选择性的非接触式气体在线测量技术。通过直接扫描多条H2O特征谱线并结合最小二乘算法实现对开放环境气体温度的在线测量。利用HITRAN光谱数据库详细讨论了边界效应对气体温度浓度测量的影响,计算结果表明,扫描多特征谱线并结合最小二乘算法可有效减小边界效应对开放环境气体温度测量的影响。实验中采用时分复用技术同时扫描了7 444.36,7 185.60,7 182.95和7 447.48cm-1四条H2O特征谱线,对管式炉573～973K范围内不同工况下的气体温度进行了测量。吸收光谱测量结果与热电偶信号的最大温差小于52.4K,温度测量最大相对误差为6.8%。     

A Wavelength Monitoring System Using Tunable MEMS Filter Calibrated by F-P Laser

We report a wavelength and power monitoring system based on a scanning MEMS filter as wavelength discriminator and a near threshold-biased Fabry-Perot diode laser as wavelength reference. This system is capable of monitoring 250 channels of DWDM signal at 25 GHz ITU Grid with an error of less than ± 8 pm.     

TDLAS痕量气体检测中激光器管壳温度对背景信号的影响

采用可调谐半导体激光吸收光谱(TDLAS)技术对痕量气体的连续检测，二次谐波背景信号会随着半导体激光器管壳温度变化产生漂移，使得二次谐波波形无法保持稳定，对测量结果产生误差。基于TDLAS原理，解释了二次谐波背景信号的产生，分析了背景信号的来源和背景漂移对测量结果的影响，通过对背景信号的扣除获得标准的二次谐波波形，设计并搭建了一套高精度恒温控制系统，此系统搭载了风冷以及水冷模块进行辅助控温，控制精度达到±0.1 ℃，选取了1 796和1 653 nm波长的DFB半导体激光器，通过控制两只激光器在20～44 ℃温度条件下来回变动，温度间隔为2 ℃，对获得的二次谐波背景信号进行了实验研究。研究表明：随着半导体激光器管壳温度上升，背景信号发生红移，反之发生蓝移；实验中温度每变化2 ℃, 1 796和1 653 nm的DFB激光器的背景信号分别产生了约3.2和2.67 pm波长漂移；通过对半导体激光器进行控温封装，实现对半导体激光器管壳的恒温控制，可以有效地消除室温变化引起的背景信号漂移，维持测量系统的稳定性，提高痕量气体检测的精度和准确度。     

Quadrature demodulation technique for self-mixing interferometry displacement sensor

A new, to the best of our knowledge, signal processing method based on quadrature demodulation technique is presented for laser diode self-mixing interferometry(LDSMI) displacement sensor. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement resolution of the laser diode self-mixing displacement sensor to a few nanometers.     

双波长自注入式光纤光栅外腔脉冲半导体激光器

提出了一种两个光纤光栅作法布里－珀罗半导体激光器的外反馈元件，在外加正弦信号的驱动下工作在增益开关状态的双波长自注入式脉冲半导体激光器。对两个波长对应的谐振腔的腔长相同与不同的两种情况进行了实验研究，并成功地获得了波长为1555．97nm和1557．9nm，脉冲宽度约为45ps和70ps，重复频率约为2GHz的双波长光脉冲信号。     

Compact,continuous-wave,singly resonant optical parametric oscillator based on periodically poled RbTiOAsO4 in a Nd:YVO4 laser

We describe a compact all-solid-state continuous-wave, singly resonant optical parametric oscillator (SRO) based on periodically poled RbTiOAsO4. The SRO is pumped at 1.064 microm by a Nd:YVO4 laser, which is itself pumped by a 3-W diode laser. Using the intracavity technique produced an oscillation threshold for the SRO of only 1.6 W (diode-laser power). For 3 W of diode pump power some 65 mW was obtained in the (nonresonant) idler (wavelength 3.52 microm). Temperature tuning over the range 10-100 degrees C resulted in tuning ranges of 1.52-1.54 and 3.41-3.54 microm for the signal and the idler waves, respectively. Importantly, relaxation oscillations were absent.     

基于可调谐二极管激光吸收光谱波长调制技术在线测量燃烧场温度

 介绍了可调谐二极管激光吸收光谱（TDLAS）波长调制技术的测温原理。通过选择水在1 397.75 nm和1 397.87 nm处两条邻近的吸收线,运用多功能数据采集卡对二极管激光器进行控制和信号采集,实现了TDLAS波长调制技术对标定燃烧炉甲烷/空气预混火焰温度的实时在线测量,测量重复频率为250 Hz。分析了温度测量数据抖动的原因,结果表明燃烧过程中火焰本身温度的抖动是测量结果波动的主要原因,测量系统的A类标准不确定度小于53 K。     

Resolution improvement in vertical-cavity-surface-emitting-laser diode interferometry based on linear least-squares estimation of phase gradients of phase-locked fringes

A frequency scanning interferometer using a vertical-cavity-surface-emitting-laser diode (VCSEL) capable of wide-frequency scanning has been constructed for precise distance measurements. The frequency scanning velocity of the VCSEL has been stabilized by the phase-locked loop technique, which enables us to precisely determine the phase gradient of the scanned interference fringe by linear least-squares fitting. In our test measurements, the absolute lengths from 8 to 14mm have been measured with a resolution of nearly sub-micrometer. Compared with a conventional frequency scanning interferometer using a Fabry-Perot laser diode, the resolution of length measurement has been improved by two orders of magnitude.