高功率重频电化学HF激光器(英文)

研制了高功率、高重频非链式HF激光器,并研究了脉冲模式和重频模式下在SF6的混合气中增加电极边缘电场强度而不使用其它措施即可实现自持体引发放电的可能性,得到了重复频率为20 Hz,脉冲能量为67 J,转换效率为3%的激光输出。     

1.8 mJ高倍率Nd:YAG板条皮秒激光放大器

设计了一种高倍率的固体皮秒脉冲激光放大器,采用Nd:YAG板条作为激光增益介质。借助板条结构的角度选通结构,搭建了板条五通放大系统,实现了对注入皮秒脉冲激光的高倍率放大。种子源工作在脉冲模式,放大器泵浦源在连续模式工作。皮秒光纤激光器可以在不同的重复频率下工作,脉冲宽度为13.4 ps。种子光经过隔离和耦合系统之后,注入板条的单脉冲能量为25 nJ。当种子源工作重复频率为24.46 MHz时,板条放大器输出平均功率377 W,单脉冲能量15.5 μJ;当种子源工作重复频率为49.8 kHz时,板条放大器输出平均功率89 W,单脉冲能量1.8 mJ,峰值功率为134 MW,放大倍率达到7.2×104。     

射频远红外波导自由电子激光器的新特性

将射频调制的超短脉冲电子束理想化为一系列δ时间函数,提出了用波导本征模展开的方法计算波导自由电子激光器中超短脉冲电子束的相干同步辐射.结果发现当谐振频率等于直线加速器射频的整数倍时,辐射模式表现为”纯”的波导本征模另外分析了超短脉冲在矩形波导中相干发射的频率特性和滑移问题,最后推导了有一定脉宽的矩形脉冲对辐射波的增益解析式.     

高峰值功率声光调Q厄米-高斯模固体激光器

在离轴泵浦激光器中,离轴热透镜效应会引起激光器出现厄米-高斯（HG）模式的跳模现象,即随着泵浦功率升高,激光器先由单一的HG模式转变为混合模式,进而跳模到相邻的低阶HG模式。这是由离轴泵浦时离轴的热透镜使谐振腔光轴发生偏移,从而使有效的离轴量减小引起的。激光器所处的模式阶数越高,发生跳模对应的泵浦功率越低。实际中可以通过对离轴量增加一个修正量,使激光器重新恢复到跳模前的模式,泵浦功率越高,需要的修正量越大。实验产生了HG_1,0～HG_16,0 16个模式的高峰值功率脉冲光束,在10 kHz重复频率下,HG_1,0光束的脉冲宽度为32 ns,峰值功率为4.1 kW;HG_16,0光束的脉冲宽度为79 ns,峰值功率为0.7 kW。     

基于增益诱导光纤激光器的实验研究及理论分析

利用非线性偏振旋转技术,实现了正色散掺铒光纤激光器的自启动锁模,产生了一种新型的增益诱导孤子脉冲输出.该类型脉冲的光谱近似为矩形,半高全宽光谱宽度可达19 nm以上,脉宽为皮秒量级.增益诱导孤子脉冲的形成是增益饱和、光谱滤波效应、腔内色散和各种非线性效应共同作用的结果.同时还分析了脉冲啁啾特性及峰值功率等参数.当抽运功率增加时,该激光器还可以实现双脉冲模式下运转. 关键词： 光纤激光器 增益诱导孤子 啁啾     

用于大尺度模型发动机高频PLIF测量的脉冲串紫外激光系统

针对大尺度模型发动机试验台工作时间短(～百毫秒到秒量级)和激光能量要求高(>1 mJ)的特点,常规的紫外激光系统不能满足发动机燃烧流场精细化测量需求,要求用于高频平面激光诱导荧光(PLIF)测量的紫外激光系统同时满足脉冲串时间间隔短和激光输出能量高,并且系统具有高可靠性和环境适应性。设计了一套用于真实发动机地面试验台高频PLIF测量的脉冲串紫外激光系统,能够获取有效的火焰动力学数据。脉冲串紫外激光系统采用自主研制的脉冲串模式激光器泵浦染料激光器,具备能量监测、波长监测和片光分布监测等功能,可以校正激光参数对测量结果的影响。其中脉冲串模式激光器采用电光调Q、脉冲串模式和MOPA技术,使输出的泵浦激光具有高脉冲能量(～50 mJ@532 nm)、短脉冲宽度(～10.8 ns)和较高的脉冲串频率(20 Hz)。脉冲串紫外激光系统的串时间间隔为50 ms,是国外激光器脉冲串间隔时间的1/200;系统整体转换效率为6%,紫外单脉冲能量为2.95 mJ@283 nm,是国外连续脉冲激光器典型能量值的7倍。为满足发动机地面试验台测量需求,自主集成了工程可用的高可靠性移动式10 kHz PLIF...     

基于少模光纤被动调Q柱矢量光光纤激光器

通过单模光纤和少模光纤熔融拉锥耦合的方法制备出模式转换器,而后将一层多壁的碳纳米管薄膜作为可饱和吸收体覆盖到拉锥光纤的锥区,形成一种可饱和吸收体柱矢量光器件.结合调Q光纤激光器和模式转换器件的优势,可以简单高效地产生脉冲柱矢量光束,并得到具有峰值功率高、模式纯度高等特点的脉冲高阶模式激光输出.通过实验实现了中心波长为1560nm、最大单脉冲能量和最大峰值功率分别为116nJ和57mW的稳定调Q脉冲输出.通过调节光路中的偏振控制器,可以分别实现径向和角向偏振的调Q脉冲激光的输出.     

电光腔倒空激光二极管抽运Nd∶YAG锁模激光器

设计了一个简单的直腔,将电光腔倒空与激光二极管端面抽运Nd∶YAG半导体可饱和吸收镜锁模激光器结合,实现了锁模脉冲的产生、放大和输出。在连续抽运功率5 W的条件下,获得了脉冲宽度为11 ps的锁模单脉冲输出和脉冲宽度为200 ns的调Q脉冲输出,腔倒空单脉冲能量为30 nJ,重复频率为10 Hz。连续锁模运转时单个锁模脉冲的能量约为2 nJ,利用腔倒空将单脉冲的能量提高了15 倍左右。文章详细讨论了腔倒空脉冲及调Q脉冲的产生机理,并分析了加在电光晶体上的高压电脉冲以及偏振片的偏振度对腔倒空脉冲及调Q脉冲的影响。     

100 kHz腔倒空薄片激光器理论与实验研究

对100 kHz运转的腔倒空薄片激光器的输出特性进行了理论和实验研究。首先建立起腔倒空薄片激光器的速率方程理论模型，模型中考虑了单位时间谐振腔中新增的自发辐射光子数，对其占总自发辐射光子数的比例进行了分析，并结合一些参数进行了仿真。进一步搭建了重复频率为100 kHz的腔倒空薄片激光器实验装置，获得了平均功率为253 W的纳秒激光脉冲输出，光光效率约为35.2%,脉冲宽度为10.4 ns,单脉冲能量为2.53 mJ,脉冲的峰值功率超过了200 kW,x和y方向的光束质量M²分别为9.77和9.27。针对腔倒空调Q的动力学稳定性问题，研究了普克尔盒开关时间对输出平均功率和输出脉冲稳定性的影响，实验中观察到了倍周期分岔和确定性混沌现象，从理论上对这个现象进行了仿真分析，仿真结果可与实验结果相符。     

电光腔倒空激光二极管抽运Nd:YAG锁模激光器

设计了一个简单的直腔。将电光腔倒空与激光二极管端面抽运Nd：YAG半导体可饱和吸收镜锁模激光器结合，实现了锁模脉冲的产生、放大和输出。在连续抽运功率5W的条件下。获得了脉冲宽度为11ps的锁模单脉冲输出和脉冲宽度为200ns的调Q脉冲输出，腔倒空单脉冲能量为30nJ，重复频率为10Hz。连续锁模运转时单个锁模脉冲的能量约为2nJ。利用腔倒空将单脉冲的能量提高了15倍左右。文章详细讨论了腔倒空脉冲及调Q脉冲的产生机理，并分析了加在电光晶体上的高压电脉冲以及偏振片的偏振度对腔倒空脉冲及调Q脉冲的影响。     

Design and experimental characterisation of a DC-excited CW/repetitively pulsed sealed off CO2 laser

This paper reports the design procedure and experimental study of a sealed off CO₂ laser. Simple algorithms for threshold and steady state excitation voltage calculation, resonator design and its temperature dependent operation are presented. The sealed off CO₂ laser was operated both in CW and pulsed modes and found stable both thermodynamically and optically. Frequency limits for pulsed operation regarding maximum and minimum output energy ranges are determined. Different aspects of CO₂ laser studied include threshold excitation voltages, temperature dependent efficiency, optical power saturation limitations, pulsed and steady state discharge currents for optimum gases mixture combinations. The laser has successfully been constructed, operated and tested for different applications within the limits of its maximum output power of 14 W.     

Theoretical prediction on the wavelength-temperature shift in pulsed TE CO2 lasers

The wavelength-temperature shift observed in pulsed TE CO₂ lasers is discussed theoretically by means of Six-temperature model rate equations for tunable TE CO₂ lasers. Numerical calculations of the temperature-wavelength shift in a pulsed TE CO₂ laser with a simple plano-concave stable resonator, whether excited by conventional low-inductance fast-discharge scheme or by a long-pulse Pulser/sustainer discharge scheme, show that the laser output wavelengths are within the 10P branch as the ambient temperature varies from 228 to 338 K, but will change as the ambient temperature varies. The laser output wavelengths will move to the transition lines with longer wavelengths in the 10P branch as the ambient temperature increases and vice versa. The calculated results also illustrate that near the ambient temperature of 310 K, the laser is more likely to operate on multi-transition lines. Considering this wavelength-temperature shift, the chilling device adopted in high-power high repetition rate TE CO₂ lasers is important in maintaining a stable laser output spectra as well as a stable laser output power. The numerical results also suggest that a frequency agile resonator is highly recommended if stable laser output spectra are required in TE CO₂ lasers.     

A DC excited waveguide multibeam CO2 laser using high frequency pre-ionization technique

High power industrial multibeam CO₂ lasers consist of a large number of closely packed parallel glass discharge tubes sharing a common plane parallel resonator. Every discharge tube forms an independent resonator. When discharge tubes of smaller diameter are used and the Fresnel numberN ≪ 1 for all resonators, they operate in waveguide mode. Waveguide modes have excellent discrimination of higher order modes. A DC excited waveguide multibeam CO₂ laser is reported having six glass discharge tubes. Simultaneous excitation of DC discharge in all sections is achieved by producing pre-ionization using an auxiliary high frequency pulsed discharge along with its other advantages. Maximum 170 W output power is obtained with all beams operating in EH₁₁ waveguide mode. The specific power of 28 W/m is much higher as compared to similar AC excited waveguide multibeam CO₂ lasers. Theoretical analysis shows that all resonators of this laser will support only EH₁₁ mode. This laser is successfully used for woodcutting     

Tunable single-mode pulsed Ti3+:Sapphire laser injection-seeded by a continuous-wave Cr3+:LiSrAlF6 laser

Spectrally pure high-power tunable single-mode operation of a pulsed Ti³⁺:sapphire laser by a tunable injection-seeding is reported. The injection laser was a cw diode laser pumped, spectrally narrowed tunable Cr³⁺:LiSrAlF₆ (Cr³⁺:LiSAF) laser with a grating in the auxiliary cavity. Single-mode tunable operation of a pulsed Ti³⁺: sapphire ring oscillator was obtained at different wavelengths in the range between 818 nm and 848 nm with a typical linewidth of 0.006 cm^-1. To extend the applicability of this operation to a differential absorption lidar system, the single-mode Ti³⁺:sapphire oscillator output was amplified and a high energy output of 38 mJ was obtained with the same linewidth.     

Simplified power supply for long pulse CO2 laser using zero cross switching technique

We propose a simple power supply for a longitudinally pulsed CO₂ laser with long pulse duration by the switching control of AC line (60 Hz) on HV leakage transformer primary, which can generate long pulse of about 3 ms compared to a typical pulsed power supply. In this power supply, a low voltage open loop control for high voltage discharge circuit is employed to avoid the HV sampling or switching, and AC line voltage switched directly by a SCR is applied to the leakage transformer primary. Thus, there is no need of a rectified bridge and an energy-storage capacitor in the discharge circuit, and the leakage transformer allows one to omit a current-limiting resistor. In order to control the laser output power, the pulse repetition rate is adjusted up to 60 Hz. A ZCS circuit and a PIC one-chip microprocessor are used to control the gate signal of SCR precisely.     

Design and operation characteristics of a high power transverse flow pulser sustained cw CO2 laser

A transverse flow, transverse discharge cw CO₂ laser in which de discharge is sustained by employing high repetition rate high voltage pulses has been developed. Pulser sustained discharge through electrodes of innovative design provided uniform excitation at electrical input power densities more than 10 W/cc. Laser output power more than 2.5 kW was obtained in a laser gas mixture consisting of 0.5 mbar of CO₂, 16 mbar of N₂ and 38.5 mbar of He. Design details and operational characteristics of this laser are presented.     

New Strong MM FIR Emissions in CH2=CF2 Pumped by a Pulsed CO2 Laser

By pumping with a suitable pulsed CO₂ laser we have produced several strong MM laser lines in 1,1 difluoroethene. All the emissions are easily identified because the emission spectroscopy is simplified in pulsed optical pumping.     

Laser annealing of silicon layers amorphized by molecular ions

The behaviour, after laser beam annealing, of heavily doped silicon layers obtained by a high current density atomic and molecular ion bombardment is investigated. The ion beam is realized by glow discharge of a gas containing the dopant, acceleration towards the sample, without any magnet.

The annealing is performed by using a high power (3.5 J/cm²) pulsed laser and the surfaces are studied by Rutherford backscattering, secondary ions mass spectroscopy and conductivity measurements. Comparison with a classical thermal annealing shows the advantage of the laser pulse to restore completely the original cristallinity, even if the layer is im-planted at doses in excess the solubility limit of the dopant, leading to a full surface amorphization.     

封离式He-N$lt;sub$gt;2$lt;/sub$gt;-CO$lt;sub$gt;2$lt;/sub$gt;激光器横模特性的测量与分析

利用激光光束分析仪,实时在线测量了一根He-N₂-CO₂封离式激光管的横模分布特性,得到了激光模式随放电电流的变化关系.实验表明该激光器在最佳工作电流时,容易形成低阶模运转,但很难获得基模运转,通过改善对称性以及加快冷却水流速可以获得基模运转.通过激光动力学过程分析了模式变化的形成原因,为大功率激光器模式控制与改善提供了一定的理论和实验借鉴. 关键词： 2激光')" href="#">CO₂激光 横模 激光模式分析 光束质量