用于制作光纤光栅的Talbot干涉仪的分析与建模

对用于制作光纤光栅的Talbot干涉仪进行了分析.当考虑准分子激光器的空间相干性和时间相干性时,几何光学中的光线法并不能给出Talbot干涉仪干涉场的真实强度分布情况,而通过光的电磁理论,则可以提供对干涉场的详细描述.基于电磁理论,建立了一个Talbot干涉仪干涉场计算模型,并首次将Talbot干涉仪的反射镜转角作为模型计算参数加以考虑,随后进行了一系列的计算.计算结果显示了干涉场的分布,同时表明空间相干性对Talbot干涉仪的近场干涉和远场干涉影响都很大,其中远场干涉对空间相干性的要求更严格,且对于远场干涉,反射镜转角的影响不可忽视.     

Formation of highly coherent radiation in a wide-aperture exciplex laser

The results of experimental investigations into the feasibility of improving the spatial and temporal coherence of the radiation of aXeCl laser with a 16×12 cm output aperture and a pulse output energy up to 150 J are given. It is shown that in the injection-locked mode, 90% of the output energy can be emitted in a narrow spectral line. An unstable resonator with mirrors small in size and generalized parameters g_i>1 allows a near-diffraction-limited beam divergence to be obtained. Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 53–56, August, 1999.     

脉冲式2 μm KTiOAsO4光参变振荡器

为了验证KTiOAsO4(KTA)晶体用于光参变振荡产生2μm激光的可行性,设计了脉冲式2μm KTA光参变振荡器,采用θ=49°切割的KTA晶体作为光参变振荡晶体,实现了2μm激光的输出;计算了该系统在双谐振情况下的起振阈值,在实验中测得输出的信号光、闲频光波长在2.16μm和2.09μm附近,与理论计算基本吻合,并测量了脉冲宽度。同时选用了对信闲光透过率分别为60%、70%、90%的镜片作为光参变振荡器(OPO)输出镜,测得了三种情况下的输出能量及电光效率的数值;测得了在380 V电压下,输出镜透过率一定时输出能量与光参变振荡器腔长之间的关系曲线,从而验证了KTA晶体用于光参变振荡产生2μm激光的可行性,为下一步的研究工作打下了基础。     

LD端面抽运Nd∶KGW 激光器热效应的理论与实验研究

对LD端面泵浦Nd∶KGW激光器的热效应进行了分析.求解热传导方程得出了Nd∶KGW晶体的温度分布和端面形变,进而计算出了热焦距随泵浦功率的变化曲线,并通过实验对其正确性进行了验证.采用凹 平腔,在不同透过率的输出镜下,对Nd∶KGW晶体的1 064 nm连续激光输出特性进行了研究.     

Longitudinal purely spatial coherence of a light field

The effects of longitudinal purely spatial coherence of light and the results of observation of these effects in an interference experiment are considered under the condition that the length of temporal coherence l _c is considerably smaller than the length of longitudinal spatial coherence ρ_‖ of the field. It is shown that, for l _c ? ρ_‖, the longitudinal purely spatial coherence of the light field in fact governs the coherence of the wave train in the process of its propagation. The length and the time of coherent (“free”) path of the wave train are considered as new spatial and temporal scales of a partially coherent light field.     

大功率部分端面抽运混合腔板条激光器

在半导体抽运的全固态激光器中,激光晶体上的热畸变限制了激光器在大功率下输出时保持高光束质量的能力。板条结构的固体激光器具有优异的散热能力,再配合部分端面抽运以及稳一非稳柱面混合腔的使用,使大功率高光束质量的激光输出成为可能。在德国EdgeWave GmbH进行的对这一技术的合作研究中,利用不到100mm的腔长,在Nd：YVO4板条激光器上获得了110W近衍射极限的1．06μm连续激光输出,这时在非稳腔方向上的光束传播因子M^2为1．3。在稳腔方向上为1．5。通过对输出激光进行空间滤波切除腔镜造成的衍射旁瓣后,50W输出时M^2的典型值在非稳腔和稳腔方向上分别为1．09和1．2。     

大功率单色LED的空间相干特性

基于van Cittert-Zernike定理,从理论上计算出大功率单色发光二极管(LED)辐出光,在空间中传输后的空间相干性分布。计算结果表明,自发辐射的LED光源其辐射光在空间中传输后,由非相干光变为部分相干光,且其空间相干性与LED芯片的结构有关。实验上采用双缝干涉对LED辐射光的空间相干性进行测量,由干涉条纹的可见度与两点间的相干度之间的关系得出,非相干LED光源的辐射光在传输后为部分相干光。而采用间隔可调的双缝干涉测量两点间的相干度后发现,LED的芯片发光区域决定了其辐射光在传输中的空间相干性分布。理论计算的空间相干性分布与实验测量结果基本吻合。     

COIL腔镜高反射率精密测量系统的可靠性分析

 利用光腔衰荡光谱技术，建立了氧碘化学激光器腔镜高反射率的精密测量系统。对用直型衰荡光腔时可能影响测量系统精度的各种因素进行了系统的实验研究。采用直型和折叠型衰荡光腔，检测了氧碘化学激光器高反腔镜在1.315μm的反射率。实验测得COIL凹面高反腔镜反射率为99.770％；平面高反镜反射率为99.917%，测量精度约为10^-5。结果表明，该系统可以精密测量氧碘化学激光器腔镜的高反射率，测量结果精确可靠。     

Laser beam patterns of an optical cavity formed by two twisted cylindrical mirrors

Propagation of an elliptical Gaussian beam in a multiple-pass optical cell formed by two twisted cylindrical mirrors has been described by means of complex curvature tensors. Using the ABCD tensor approach various light patterns were computed for the use in tunable laser absorption spectroscopy with a multiple-pass optical cell. Light patterns with high beam-spot density can be also defined for a cavity formed by two twisted cylindrical high-reflectivity mirrors. In order to achieve higher cavity output intensity, a high-reflectivity cylindrical mirror cavity with at least one mirror that has a central transparent spot for laser beam injection has been described for applications in non-resonant cavity enhanced absorption spectroscopy. The author was with TDL Sensors Ltd., when the experimental part of this work was performed.     

Temporal evolution of the xenon laser pulse

An experimental investigation was made of the xenon excimer laser. Several laser cavities have been employed with excitation by electron beams of cross section (15×2) cm² and (55×4) cm² and current density 100–150 A cm^-2 injected transverse to the cavity axis. A numerical model of the xenon laser is compared with experimental results. The laser pulse width was found to be dependent on laser intensity and cavity mirrors. Early termination of the laser pulse was observed consistent with changing reflectivity of the cavity mirrors. An uncoated MgF₂ retroreflector produced a laser output of significantly longer pulse width. Quasi-cw laser action was observed.     

LD泵浦掺镱双包层光纤激光器的理论研究

对线形腔LD泵浦掺镱的双包层光纤激光器进行研究,通过数值模拟,分析了不同泵浦方式下的泵浦光、激光输出功率和增益特性在光纤中的分布。结果表明,单端后向泵浦输出功率率较高,对于小功率光纤激光器则是最佳选择。进一步又研究了单端后向对称泵浦输出功率与光纤长度及腔镜反射率的影响,为提高光纤激光器的输出功率提供了理论和实验依据。     

Study of modulation instability in a temporally incoherent photorefractive ring resonator below the threshold with incoherent light

Modulation instability (MI) and evolution of pattern formation inside a passive non-linear photorefractive ring resonator having cavity-length longer than the coherence length of the light circulating in the resonating cavity has been theoretically analyzed. Dynamics of the system below the threshold conditions have also been analyzed, numerically using linear perturbation theory for the Kerr-type non-linearity. The process of modulation instability in a temporally incoherent cavity below the cavity threshold and the influence of various parameters such as the cavity-length, intensity feedback of the perturbed wave field, amplitude of the incoming beam and spatial frequency on the gain factor and the spatial spectral density have also been studied. For the perturbed wave field, it has been found that the growth rate of MI increases with increase in the intensity feedback as well as the spatial frequency. It has also been found that increasing the intensity feedback of the perturbed wave field, for a given value of the spatial frequency, the spatial spectral density of the perturbation at the output of the non-linear medium increases with the shifting peak positions to the higher spatial frequency side.     

部分相干光经柱面球差透镜聚焦所产生的焦移

利用Collins公式得出光强均匀部分相干光经柱面球差透镜聚焦后的轴上光强分布,并通过数值模拟的方法研究了入射光的菲涅耳数、相干度和透镜的球差对轴上点光强分布的影响.结果显示,当菲涅耳数较小、空间相干度较小的部分相干光经无球差透镜聚焦时,轴上点光强分布会产生焦移现象,而当部分相干光被球差透镜聚焦时,也会有焦移现象产生.     

高功率激光器腔镜热变形对输出光束质量的影响

利用有限元分析法结合Fox-Li迭代法,考虑腔内本征模式与腔镜热形变的相互耦合作用,计算模拟了正支共焦非稳腔的本征模式分布,定量分析了高功率激光器腔镜热变形对输出光束质量的影响,重点讨论了腔镜热变形所引起的腔内本征模式相位特性的变化,并从波前功率谱密度、Zernike像差系数及光束质量值等角度对腔镜发生热形变前后的激光器输出光束的光束特性进行比较分析。研究结果表明:高功率激光器腔镜热形变对输出光束的光束质量会产生一定的影响,且随着激光输出功率的增大,镜面热形变引起的输出光束波前相位高频比例及Zernike高阶像差均会有所增大,波前畸变程度也明显变大,光束质量逐渐变差。     

100 W Kinetically enhanced copper vapor laser at 10 kHz repetition-rate, high (∼1.5%) efficiency with low (∼1.6 kW/l) specific input power and performance of new resonator configurations

It is established here that kinetically enhanced copper vapor lasers (KE-CVLs) based on large-bore discharge tubes can provide high (>1.4%) efficiency at ∼9-10 kHz rep-rate with very low (<2 kW/l) specific input power. Comparative performance of various large-bore kinetically enhanced copper vapor lasers in the range 45-70 mm is presented for most suitable discharge tube. Maximum output power of ∼100 W was achieved with efficiency of about 1.55% at 10 kHz rep-rate from the 60 mm bore KE-CVL. The pulse to pulse efficiency of the KE-CVL was ∼2%, tube efficiency ∼2.1%, and laser pulse energy was about ∼10 mJ. These results show significant advancement in the laser system as an elemental high temperature CVL due to volumetric scaling and KE-effects combined with very low specific input power of ∼1.65 kW/l as compared to 8-9 kW/l normally required in other kinetically enhanced copper vapor lasers to generate ∼100 W output power. Performance of the KE-CVL with 3 new cavity configurations namely, (1) CAT-EYE resonator (2) hybrid resonator, and (3) modified diffraction coupled resonator with dot mirrors are presented for the first here. CAT-EYE resonator was demonstrated to achieve high misalignment tolerance without significant loss of power. A typical drift in power of ∼5% was observed with misalignment responsible for 40% decline in power in case of standard plane-plane cavity. Effect of resonator misalignment on amplifier output drift was also investigated using CAT-EYE resonator in oscillator-amplifier configuration. In case of using stable-unstable hybrid resonator, high magnification of M ∼ 1500 was realized resulting in extremely low divergence (∼0.08 mrad) beam with modest (∼20%) loss in average power. In case of modified DCR cavity, record power of about 48 W was achieved with beam divergence of about 0.1 mrad on using intra-cavity 2 × 2 array of 4 dot mirrors.     

Demonstration of temporal coherence,spatial coherence,and threshold effects in the molecular xenon laser

Stimulated emission has been observed at 1722 ± 1 Å in high-pressure xenon gas originating from the bound-free continuum of the Xe¹₂ molecule. This emission exhibits strong line narrowing, spatial coherence corresponding to a few times the diffraction limit, a sharp oscillation threshold, and an output time dependence radically different from the spontaneous emission observed without an optical cavity or below threshold. The confluence of all these observations is an explicit and unequivocal demonstration of a coherent stimulated emission process. Specific data detailing the pressure dependence of the stimulated output and results with rare-gas mixtures are given.     

3–5 μm AgGaS2 optical parametric oscillator with prism cavity

Employing a coated right-angled sapphire prism as the OPO cavity mirror, AgGaS₂ type-I singly resonant optical parametric oscillator was demonstrated experimentally, which was pumped by a ns 1.064 μm Nd:YAG laser. Continuously tunable 2.35 to 5.27 μm radiation without changing cavity mirrors and maximum output energy 0.58 mJ per pulse are recorded.     

Study of gas detection based on integrated cavity output spectroscopy

A trace gases detection system based on integrated cavity output spectroscopy (ICOS) was developed, where a NIR tunable diode laser (TDL) was used as light source, an optical cavity composed by two plan-concave mirrors with reflection near 99.7% was used as the absorption cell. Trace water vapour (H₂O), carbon dioxide (CO₂), methane (CH₄), carbon monoxide (CO) and mixture of CO₂ and CO were tested by ICOS based on the characteristics absorption. The wavelength calibration, cavity transmission characteristics, quantitative measurement ability and sensitivity of the TDL-ICOS were also studied, and a evaluated minimum detectable sensitivity of 1.15 × 10^?7 cm^?1 was obtained when the system was used to CH₄ detection. The experiment results show that TDL-ICOS is expected to be a reliable and promising system for the detection of trace gases since it has some advantages such as real-time monitoring, simple device, easy operation, high sensitivity, good stability and quantitative ability.     

Sub-20-fs terawatt-class laser system with a mirrorless regenerative amplifier and an adaptive phase controller

We have developed an ultrabroadband regenerative amplifier with a mirrorless cavity to eliminate the limitation of bandwidth of dielectric coats on cavity mirrors. The large amount of material dispersion in the Pellin-Broca prisms that are used instead of cavity mirrors is compensated for with a hybrid technique that uses Brewster prism pairs in the regenerative amplifier and an adaptive phase controller of a liquid-crystal spatial light modulator. We obtained a 16-fs pulse width with an energy of 13 mJ, which is to our knowledge the highest energy obtained in the sub-20-fs regime by use of an adaptive phase controller.     

Highly selective terahertz optical frequency comb generator

Using a 10.5-GHz resonant electro-optic modulator placed inside a resonant optical cavity, we generated an optical frequency comb with a span wider than 3 THz. The optical resonator consists of three mirrors, with the output coupler being a thin Fabry-Perot cavity with a free spectral range of 2 THz and a finesse of 400. Tuning this filter cavity onto resonance with a particular high-order sideband permits efficient output coupling of the desired sideband power from the comb generator, while keeping all other sidebands inside for continued comb generation. This spectrally pure output light was then heterodyne detected by another laser with a frequency offset of the order of 1 THz.