结合塞曼效应与饱和吸收技术的DFB激光稳频系统的设计

本文介绍一种利用塞曼效应与饱和吸收相结合的技术提取激光频率误差信号的方法,利用数字PID控制技术,伺服反馈于DFB激光器的电流调制端实现慢环控制,模拟PI反馈于激光器FET电流控制端,实现快环控制,从而实现DFB激光器的稳频和线宽压窄。系统的激光频率锁定在铯原子D2饱和吸收谱线F=4→F’4,5交叉线上,频率峰-峰（p—p）起伏约为1．6MHz,相对频率起伏为4．5×10^-9,满足小型喷泉钟的使用要求。     

DFB光纤激光器声致弯曲振动研究

对利用DFB（分布反馈式）光纤激光器进行水声探测时的弯曲振动问题进行了分析与实验研究。总结了采用非平衡干涉仪解调系统解调的DFB光纤激光水听器的声压灵敏度计算公式;基于梁的弯曲理论,通过数值方法计算了两端固定的DFB光纤激光器在50Hz～2000Hz频率范围内的声压灵敏度,绘制了该频率范围内的频响曲线：采用振动液枉法对一支DFB光纤激光器在该频率范围内进行了实验研究,实验数据具有良好的可重复性,实验结果与理论分析吻合。表明了细长型结构的DFB光纤激光器在水声场中很容易由于弯曲振动而引入较大的非声压振动的干扰信号,影响其水声探测性能,有必要在DFB光纤激光水听器探头的设计中考虑这一因素。     

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Sagnac环形滤波器的多波长掺铥光纤激光器

为了实现2μm波段多波长激光输出,提出并设计了一种基于Sagnac环形滤波结构的多波长掺铥光纤激光器.激光器由波长793 nm的泵浦源、波分复用器、光纤耦合器、保偏光纤、掺铥光纤以及偏振控制器构成,其中Sagnac环形滤波器以及光纤环形镜作为激光器的反射端.实验中,激光器工作阈值为77.5 m W,通过调节偏振控制器,实现了稳定的单波长激光输出.波长为1 852.8 nm的单波长激光输出时,在50 min监测时间内波长最大漂移为0.1 nm,功率最大漂移为0.252 d B,激光3 d B线宽和信噪比分别为0.3 nm和35.7 d B.通过调节偏振控制器,在1 850~1 900 nm光谱范围内实现了1~4波长的激光输出.     

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     

准分子激光器用含氟混合气体配制与净化装置的建立

根据准分子激光器的使用要求,建立了一套准分子激光器用含氟混合气体配制与净化装置,并规定了操作规程.按规程应用该装置配制的含氟混合气,可以使准分子激光器的有效工作时间延长2～3倍,激光器中镜面的使用寿命平均延长3～5倍.实践证明,该装置的建立是可行的.     

室温准连续多量子阱二极管激光器调谐特性

为了将应变补偿多量子阱（SC-MQW）激光器用于调谐激光吸收光谱（TDLAS）技术进行气体分子检测,研究了SC-MQW激光器在室温、准连续工作模式下的调谐特性.从半导体激光器的速率方程出发,分析了SC-MQW激光器输出波长与温度和注入电流的关系;使用傅里叶变换红外光谱仪（FT-IR）测量了激光器分别在不同电流、温度条件下的调谐特性,得到SC-MQW激光器在允许工作电流范围内的调谐范围接近20nm,电流调谐率约为0.03nm/mA;温度调谐率约为0.25nm/℃;电流和温度联合调谐的波长覆盖范围达50nm.结果表明,该激光器在带状吸收谱的挥发性有机物气体检测方面有很好的应用前景.     

光纤饱和吸收体稳频窄线宽光纤激光器

结合光纤饱和吸收体与光纤光栅法布里-珀罗标准具,研制出了全光纤结构1550nm单频窄线宽掺铒光纤环形激光器.采用两个976nm激光二极管双向抽运作为抽运源,高掺杂浓度铒光纤作为增益介质,以行波腔消除空间烧孔效应,利用光纤光栅法布里-珀罗标准具窄带选模特性,以10m长低掺铒光纤饱和吸收体稳频,得到了十分稳定的窄线宽激光输出.激光器抽运阈值功率21mW,在抽运光功率为145mW时输出光功率39mW,斜率效率30%,信噪比大于50dB.采用延迟自外差方法精确测量光纤激光器线宽小于10kHz.     

激光泵浦的铯-氦磁力仪的信号特征

研究了基于激光泵浦的铯-氦磁力仪的磁共振信号特征。通过使用窄线宽激光对铯原子进行泵浦,得到了12.3 A/T的电流-磁场转换因子,与基于放电灯泵浦的铯-氦磁力仪相比,转化效率增大13.5倍。实验发现通过间接泵浦,可消除“光致展宽”。通过分析线宽的实验值和理论值,得到实验值线宽的最大展宽来自于脉冲激励的结论。通过测量光源、磁场、光电传感器和电路的本底噪声,确定了该磁力仪最大的噪声源为光源和磁场,以磁场分辨力为优化目标得到了最佳光强,铯-氦磁力仪的磁场分辨力可以达到0.05 nT。     

基于DSHI的窄线宽光纤激光器线宽测量

窄线宽光纤激光器的线宽作为相干光学系统的重要参数需要进行准确的测定,延时自外差法(DSHI)是测量窄线宽比较理想的方法.本文讨论了DSHI测量线宽的基本原理,根据DSHI的功率谱表达式,利用MATLAB程序对不同光纤延迟线长度条件下的DSHI功率谱进行了仿真,并分析和讨论了光纤延迟线长度对线宽测量结果的影响.建立了1550 nm波长的DSHI线宽测量系统,对IPG公司的光纤激光器线宽进行了测量.该系统用示波器代替频谱仪,并采用FFT软件算法对示波器获取的光电流信号进行分析,测得该激光器的线宽约为16 kHZ,在理想的精度范围内.     

Correlation between 1/f noise and semiconductor laser degradation

The origin of the increase in residual spectral linewidth during device degradation is experimentally and theoretically clarified in a multiple quantum well (MQW) distributed feedback (DFB) laser. Non-radiative recombination current increases during device degradation and causes 1/f noise to increase. This current 1/f noise is the origin of the increase in the residual spectral linewidth. Through these degradation behaviours, a model showing a correlation between 1/f noise and the semiconductor laser degradation is proposed.     

Holographic DFB Dye Lasers

A new simple type of DFB dye laser is proposed. The laser consists of a dye cell and a transparent phase holographic grating mounted on the front window of the cell. In the experiment, high-quality stable transparent holographic gratings were recorded in bichromated gelatine with a single mode He-Cd laser. When pumped perpendicular to the surface of the grating the DFB laser emitted a narrow spectral line independently of the width and the position of the pump spectrum. A linewidth of 0·01 nm was measured under pumping with broadband radiation of 20 nm spectral width. Either a set of holographic gratings of a different period or a fan-shaped grating may be used in the laser for stepped or continuous spectral tuning.     

Progress in the realization of a frequency standard at 192.1 THz(1560.5 nm) using 87Rb D2-line and second harmonicgeneration

Second harmonic generation of a 192.1 THz semiconductor distributed feedback (DFB) laser is achieved using a KNbO₃ crystal in a resonant ring cavity. Optical feedback from this cavity is used to stabilize the laser frequency and reduce its linewidth. A second harmonic power of 5.5 μW is generated with 38 mW incident on the cavity. We use the second harmonic signal to observe saturated absorption lines and orientation signals in rubidium vapor. Injection-locking of a 780 nm Fabry-Perot laser using the second harmonic signal is also demonstrated. With this scheme, we observe saturated absorption lines in rubidium     

Linewidth-determining Processes in Distributed Feedback Dye Lasers

Abstract

Processes determining the linewidths of distributed feedback dye lasers (DFDL) have been investigated. Time resolution of the frequency of the output pulse shows that the linewidth, averaged over a pulse, arises predominantly from a dynamic sweeping of the laser frequency during the course of the pulse. This sweeping results from refractive-index changes in the dye over the duration of the pumping pulse; either through thermal effects or dispersion associated with the saturated gain. Thermal effects may be minimized by suitable choice of solvent but the dispersive sweep is inherent in this type of laser. The magnitude of the dispersive sweep changes across the tuning range of the laser. By judicious choice of dye solvent and dye parameters we have developed a narrow linewidth DFDL of 140 MHz for τ = 3·2 ns pulses, which is close to the transform limit.     

Fabrication of a distributed-feedback dye laser with a grating structure in its plastic waveguide

Two approaches of fabricating grating structures for waveguided plastic dye lasers are described and compared for lasing performance. Rhodamine6G-doped poly(methyl methacrylate) (PMMA) film on a PMMA substrate was used for the waveguide, and a distributed-feedback (DFB) laser operation with a single-propagation mode was demonstrated. The performances of both types of permanent grating structured DFB dye laser were better than those of a DFB dye laser on a plain waveguide with a dynamic grating formed by the interference of two pump beams. Wide tuning range is expected by use of a multistripe DFB laser with different grating pitches.     

Fiber distributed-feedback lasers used as acoustic sensors in air

Contributions to the acoustic signal sensitivity of fiber distributed-feedback (DFB) lasers in air are investigated both theoretically and experimentally. The theoretical results show that the dominant contribution to the laser frequency shift comes from adiabatic temperature shifts in the surrounding air at lower frequencies and from pressure at higher frequencies. The transition frequency was found to be between 5 and 20 kHz, depending on the elastic boundary conditions of the fiber laser. The acoustically induced frequency shifts of two fiber DFB lasers were measured, and the sensitivities varied from 0.61 MHz/Pa at a 100-Hz acoustic frequency to 0.34 kHz/Pa at a 15-kHz acoustic frequency.     

Dual-wavelength diode-seeded Ti:sapphire laser for differential absorption lidar applications

A dual-wavelength, diode-seeded, flash-lamp-pumped Ti:sapphire laser system has been developed. Injection seeding allowed the attainment of high output energies (130 mJ), narrow linewidth (250 MHz), and high reliability. Furthermore, an original method is presented for dual-wavelength operation, using diode current sweeping. These specifications are ideal for differential absorption lidar applications, and the example of NO(2) detection is presented. Extension to other pollutants is discussed.     

Threshold analysis of a chirped-grating distributed-feedback laser with the power series method

A new and efficient method for analyzing a chirped-grating distributed-feedback (DFB) laser is presented. We show that coupled-wave equations can be solved by use of the power series method. The single-mode gain margin of a linearly chirped-grating DFB laser is calculated for different chirping factors and coupling constants. We found that clearly optimum chirping exists for which the single-mode gain margin is maximum. The gain margins were also calculated for different positions of the cavity center. The effect of facet reflectivities and their phases on the gain margin was investigated. We found that the gain margin is maximum and the spatial hole burning is minimum for the cavity center at the middle of the laser cavity.     

Narrow-linewidth, multi-Watt Yb-doped fiber amplifier at 1014.8 nm

We report on an efficient, narrow linewidth, two-stage fiber amplifier at 1014.8 nm based on Yb-doped double-clad fibers. The fibers are cooled to liquid-nitrogen temperatures in order to suppress absorption at the operating wavelength. We achieved output powers of up to 5.0 W at a linewidth of less than 3 MHz by seeding the amplifier with the radiation from an external cavity diode laser.