Semiconductor optical amplifier based swept wavelength source at 1060 nm using a scanning Fabry-Perot filter and an YDFA-based booster amplifier

We demonstrate a tuneable laser operating in the 1-1.1 μm wavelength region with a tuning range of 43 nm (FWHM), an output power of 19 mW and coherence length of 14 mm. The source is based on a master laser consisting of a cavity tuned ring configuration with a fibre Fabry-Perot filter used as a tuning element and a semiconductor amplifier as gain medium. The output of the master laser is subsequently power boosted using an Ytterbium doped fibre amplifier (YDFA). In addition to providing a power boost, we demonstrate that by tailoring the gain spectrum of the YDFA it is possible to increase the FWHM scanning range by 7 nm compared to that of the master laser.     

High-power ultraviolet 278 nm laser from fourth-harmonic generation of a Nd:YAG laser in CsB3O5

We demonstrate a high-power UV 278 nm laser by fourth-harmonic generation (FHG) of a 1112 nm Nd:YAG laser in a nonlinear optical (NLO) crystal CsB3O5 (CBO) for the first time, to our best knowledge. A 30 W level diode-pumped Q-switched Nd:YAG laser at 1112 nm with beam quality factor M2=1.2 was used as the fundamental light source at a pulse width of 500 ns. With an LiB3O5 crystal, the 1112 nm laser was first frequency-doubled to 556 nm with an average output power of 13.5 W. It was then frequency doubled again in a CBO crystal to obtain the FHG output at 278 nm. The maximum average output power of the 278 nm laser is up to 1.5 W. The results demonstrated that CBO crystal is a promising NLO material for UV high-power lasers below 300 nm.     

1064nm超短腔DBR单频掺镱硅酸盐光纤激光器

提出了一种基于高掺杂硅酸盐增益光纤、输出波长为1 064nm的超短腔单频光纤激光器.该单频光纤激光器采用分布布拉格反射式腔型结构,有效腔长为2cm,其增益介质为1.1cm长的高浓度掺Yb3+光纤.通过恰当的温度控制,获得了线宽为4.8kHz的稳定单频激光输出.当注入泵浦光为378mW时,输出功率为13mW,斜效率为3.4%.在频率大于1 MHz时,测得该光纤激光器的相对噪声强度值约为-132dB/Hz.采用主振荡功率放大结构,对该单频光纤激光器的输出功率进行放大.当放大增益光纤长度选取为56cm时,得到了325mW的最大输出功率,其斜效率为52.8%.     

Effect of steady-state conditions on self-pulsing characteristics of Yb-doped cw fiber lasers

Fiber laser resonator configurations have been analyzed theoretically on the basis of steady-state rate equations to optimize the laser conversion efficiency. Evolution of the pump- and signal powers and the saturated gain coefficient along the length of the laser medium has been simulated for high- and low-finesse resonators in forward- and backward pumping schemes. The corresponding fiber laser configurations have been setup to verify the results of simulation. Backward pumping configuration in an Yb-doped fiber laser has been found to be the most efficient, and in this configuration a maximum cw output power of 10.75 W in single transverse mode with an optical-to-optical conversion efficiency of 62.5% has been achieved. The laser output spectrum was peaked at 1093 nm with full-width at half-maximum (FWHM) line-width of about 9 nm. In the low-finesse resonator configuration, it has been found that experimental observations differ from theoretical simulation results. In this case, output power from both ends ceases to increase linearly beyond 1.8 W, and starts fluctuating due to the onset of strong random self-pulsing phenomenon. Our investigation shows that a non-uniform steady-state gain along the fiber length facilitates the self-pulsing process.     

O2(1Δg)二聚物激光振荡研究

从理论上估算了O2(1Δg)二聚物激光输出功率,在实验中以微波(2.450 GHz)激励高纯氧产生02(1Δg)二聚物,采用平凹稳定谐振腔,首次在波长6561 nm处实现了O2(1Δg)二聚物的激光振荡,当充入氧气压强为133.3 Pa,微波激励功率为600 W时,激光输出功率可达100 μW,此结果在数量级上与理论估算相同.另外还测得激光束散角约37.3 mrad.     

一种结构新颖的L波段掺铒光纤激光器

提出了一种结构新颖的L波段环形腔掺铒光纤激光器。用掺铒光纤作为增益介,采用980nm激光器作为前向抽运源,利用起偏器和偏振控制器获得L波段激光,利用光环形器将后向的放大自发辐射再引入铒光纤的前端,重复利用。当抽运功率为103mW时得到了阈值功率约为23．87mW,输出功率达6．34mW的激光输出,斜率效率约为8．05％,与没有重复利用后向放大自发辐射谱的掺铒光纤激光器做比较,该结构对L波段掺铒光纤激光器的性能有明显的提升作用。对于长度不合适的铒纤,在没有重复利用后向放大自发辐射谱时没有获得激光输出;而在利用后向放大自发辐射后,在阈值功率约为88mW时得到了激光输出,从而很好地证明了上述结论。     

基于光纤中SBS相位共轭的自调Q光纤激光器

分析了利用光纤中的受激布里渊散射(stimulated Brillouin scattering,SBS)相位共轭效应进行激光腔内调Q,产生ns量级脉冲激光的原理,并对利用该效应产生的激光脉冲波形和脉冲形成过程进行了数值模拟,得到的脉冲波形与SBS相位共轭反射率随时间变化曲线基本一致,表明利用光纤中的SBS相位共轭作用调Q具有可行性.据此,对采用单模光纤(single-mode fiber,SMF)作为SBS池的Er³⁺掺杂调Q光纤激光器进行实验研究.当单模光纤长度为1.5 m时,在45 mW的光抽运功率下得到脉宽约2.6ns,脉冲周期58.23ns,平均功率7.35mW的激光脉冲.进一步的研究表明:激光器中相位共轭镜的形成与SBS介质长度有关,SBS介质过长,斯托克斯线之间无固定的相位关系,不能形成相干叠加,SBS相位共轭腔不能形成;SBS介质过短,腔内正交偏振模光子寿命的改变使脉冲出现双峰现象.脉冲形成后其属性只与SBS动态属性有关.     

新型全固态激光器作用过程中的激光参数分析

对影响LD泵浦的Nd∶GdVO4,Nd∶YVO4和Nd∶YAG激光器输出特性的增益介质长度、腔内损耗、输出镜透过率、泵浦光和振荡光的光斑大小进行了分析和数值模拟。当腔内固有损耗为2%,输出镜透过率为10%时,Nd∶Gd-VO4,Nd∶YVO4和Nd∶YAG晶体的振荡阈值分别为1.77W、0.55W和3.34W。在25W泵浦功率下,利用1mm长的Nd∶GdVO4,Nd∶YVO4和Nd∶YAG晶体可分别得到13.17W,13.26W和8.43W的输出功率,相应的输出镜最佳透过率分别为24%,44%和16%。     

新型准分子——O2(1Δg)二聚物增益特性的研究

本文从理论上估算了O2(1Δg)二聚物的增益系数,在实验中以微波(2450 MHz)激励产生激发态(1Δg)的氧分子,利用放大的自发辐射法,首次获得了波长为6561nm处介质的增益特性曲线。当气压为0.3 torr,激发功率为300W时,净增益为0.0183cm-1可望实现激光振荡。     

不同振荡放大比MOPA型化学激光器的数值模拟

主振功率放大型装置在高能激光器中有着广泛的应用, 在增益体积和沿光轴方向增益长度一定的情况下, 为了得到高能化学激光器主振部分和放大级部分的最佳比例, 研究了不同振荡放大比对输出光束的近场强度以及最终输出功率的影响. 使用快速傅里叶变换的算法经过迭代计算得到了1:4, 1:1, 2:1三种振荡放大比情况下的近场光束强度分布, 并计算了其强度分布均匀性及最终输出功率情况. 计算结果表明: 采用MOPA 结构的氟化氘化学激光器, 振荡放大比越大, 主振荡部分输出的能量越高, 谐振腔内功率密度越大, 对腔内镜片的承受能力要求越高; 而振荡放大比越小最终输出光束的衍射放大效应越明显, 对光束质量越不利. 在本文条件下, 计算结果还表明, 振荡放大比对功率会产生影响, 存在一个最佳的比例使得输出功率最大. 振荡放大比对输出功率的影响随主振部分输出耦合率, 光路中的各种损耗, 增益的规模等多种参数的不同而变化, 工程运用中可根据具体参数进行计算. 关键词： 主振功率放大 光学谐振腔 近场强度 光束质量     

O_2（~1△_g）二聚物的兰色激光振荡

通过微波（２．４５０ＧＨｚ）激励高纯氧产生Ｏ２（１△ｇ）二聚物，利用放大自发辐射法首次测得了Ｏ２（１△ｇ）二聚物在４８６ｎｍ处的小信号增益系数。采用平凹稳定谐振腔观察到了４８６ｎｍ的兰色激光振荡，最大激光输出功率为１３０μＷ，发散角为２８ｍｒａｄ。     

Theoretical application of z-dependent gain coefficient to describe amplified spontaneous emission

Based on the geometrical modeling of the unified gain coefficient and the reported amplified spontaneous emission (ASE) output energy measurement ε(ASE) versus amplifying excitation length, l(AMP) in a KrF laser oscillator, we managed, as an example, to explain the ASE output energy behavior both numerically and analytically. In this approach, introducing the ASE gain-coefficient profile for the KrF laser, g(0,KrF)(ASE), was not avoidable. It was found that while the g(0,KrF)(ASE) profile follows the introduced gain-modeling formulation, it is, however, slightly lower than the KrF laser gain profile, g(0,KrF)(exp), deduced from the measurements reported by different researchers. The present approach, up to the present time, is able to explain all of the existing ambiguities on understanding the ASE behavior.     

888nm LD泵浦Nd：LuV04倍频绿光激光器

报道了采用888nIn的激光二极管（LD）泵浦Nd：LuVO4晶体得到1066nm的激光输出,其对应能级跃迁为4F3／2→4I11/2。在注入的泵浦功率为18．2W时,获得了11．3W的近红外1066nm激光输出;然后采用非线性晶体LiB。O。（LBO）进行腔内倍频,获得了533nm的绿激光输出,输出功率为4．3W,其光-光转换效率为23．6％,光束质量因子为M2=1．3,4h功率稳定度优于3．7％。     

15波长输出的布里渊掺铒光纤激光器

多波长布里渊掺铒光纤激光器是一种新型的多波长光纤激光器,其原理是利用受激布里渊增益和掺铒光纤的线性增益,可以在常温下得到波长间隔约为0．08nm(～10GHz)的多波长输出。报道的布里渊掺铒光纤激光器,在布里渊抽运功率为1．7mW、980nm抽运功率为300mW的情况下得到稳定的15个波长(间隔～10GHz)的输出,这种激光器用作光传感器、光谱分析仪以及密集波分复用系统的光源。实验发现,输出波长的个数随着980nm抽运功率的增大而增加。另外,布里渊掺铒光纤激光器的信号功率主要来自于掺铒光纤的增益,而布里渊增益对它的影响不大。     

Medium power single-mode single-wavelength fiber laser

Medium-power, single-mode, single-wavelength fiber laser working at room temperature using a polarization-maintaining erbium-ytterbium co-doped fiber as the gain medium, and an un-pumped elliptical core erbium-doped fiber as a saturable absorber to reduce linewidth and mode hopping of the lasing wavelength is reported. The effects of length, erbium ion concentration, and polarization-maintaining property of the saturable absorber were explored. The output power of the laser was more than 100 mW and the lasing line was stable for more than 3 h with an intensity fluctuation of less than 0.2 dB. The laser linewidth (FWHM = Full width at half maximum) was 7.5 MHz and the signal to noise ratio was more than 50 dB. The output of the laser was measured using an optical spectrum analyzer (OSA) of resolution 1.25 GHz and a scanning Fabry-Perot spectrum analyzer (SFPSA) of resolution 6.7 MHz.     

Small-signal gain dependence on active medium length and axial thermal profile in metal-vapor lasers

We measure the small-signal gain coefficient g ₀ of a gold vapor laser for a 627.8 nm transition through the implementation of a discharge-driven oscillator-amplifier configuration. We study the gain dependence on the length of the laser active medium. In addition, we measure the output power of a copper-vapor laser for two different thermal insulator distributions and simulate the thermal-length profile to determine the effective length of the active medium. We show that the small-signal gain coefficient depends on the effective length of the active medium and do not depend on the physical (actual) length of the active medium.     

用声光调制器实现的1 W Nd∶YAG单纵模环形激光器

鉴于单向环形腔是目前获得较大功率单纵模激光最有效的方式之一,为使环形腔单向运行,需要在环形腔内插入对正反2个方向的光产生损耗差的光学元件。采用激光二极管泵浦Nd∶YAG晶体,用声光调制器作为光学二极管使环形腔单向运行,实现四镜矩形环形腔单纵模激光器。实验中谐振腔的稳定性由增益介质的热透镜保证,声光调制器给正反2个方向的光提供损耗差,这使得在竞争过程中有较大损耗的光不能运行从而获得单向输出。实验获得了连续功率1 W、光束质量因子M2为1.21 的1.06 m单纵模激光。     

High-performance,compact, prismless,low-threshold 30-MHz Ti:Al2O3 laser

We describe the design and operation of a compact femtosecond Ti:Al2O3 laser based on a novel multipass cavity (MPC) design. The laser is all solid state, has prismless dispersion compensation with double-chirped mirrors, and uses a tight-focusing geometry to facilitate efficient low-threshold operation. We increase output pulse energies by extending the resonator length with a compact, scalable MPC, which preserves the characteristics of the Gaussian beam for the short cavity. Although the effective cavity length is approximately 5 m, an extremely compact laser that measures only 30 cm x 45 cm is achieved. With only 1.5 W of pump power, the laser generates 23-fs pulses at a repetition rate of 31.25 MHz and with 88 mW of average output power, corresponding to 2.8 nJ of pulse energy.     

Dual-wavelength high-power Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating

We report a high-power dual-wavelength Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating (FMFBG). The FMFBG was fabricated by using a piece of fiber in a length of fiber with a cutoff wavelength of 1225 nm, which supported two modes at 1060 nm. The laser was pumped by a fiber pigtailed laser diode working at 915 nm. Single-wavelength, dual-wavelength and triple-wavelength laser oscillations were observed when the fiber laser operated under different low pump powers. However, stable dual-wavelength operation was achieved at higher pump power of 3.9 W and remained unchanged until the output power reached 5.67 W under the maximum available pump power of 10.7 W. The laser wavelengths were centered at 1059.12 and 1060.80 nm with a full-width at half-maximum of 37 and 43 pm, respectively. The signal-to-noise-ratio was greater than 50 dB and the beam quality factor (M²) was about 1.9.     

高恢复压力氟化氘增益发生器技术研究

增益发生器是影响高能氟化氘(DF)化学激光器恢复压力的核心组件,采用传统增益发生器的DF激光器尾气恢复压力约为6.7 kPa。设计了一种紧凑化TRIP型增益发生器,突破了高腔压运转、主气流气幕和激射腔边壁回流抑制等关键技术,实现了DF激光器尾气恢复压力的大幅提高。实验结果表明,在面积比流量为1.3~3.3 g·s-1·cm-2的范围内,随着增益发生器面积比流量的提高,激光器尾气恢复压力有效提高,面积比功率持续增加;在面积比流量为3.3 g·s-1·cm-2条件下,DF激光器可以实现26.7 kPa背压(海拔10 km大气压)下的高效运行。