Microchip optical parametric oscillators

The frequency-doubled output of a high-power passively Q-switched Nd:YAG microchip laser has been used to pump a KTP doubly resonant miniature monolithic Fabry-Perot (microchip) optical parametric oscillator (OPO). The OPO operated with 20% conversion efficiency, generating 8.4 /spl mu/J of 1.064-/spl mu/m radiation in 600-ps pulses, with excellent mode quality and pulse-to-pulse stability. This is the most compact OPO system yet demonstrated, generating the shortest pulses reported for an OPO pumped with Q-switched pulses. This technology makes it possible to obtain miniature optical system operating at any wavelength throughout the near IR, visible, and UV.     

Tunable optical parametric oscillators

This paper reviews progress on tunable optical parametric oscillators. Topics considered include: parametric amplification of Gaussian beams: threshold; tuning techniques, spectral output, and stability; saturation and power output; spontaneous parametric emission; nonlinear materials; and far infrared generation.     

光参量振荡器中的多频振荡

在双谐光参量振荡器中,首次在信号和空闲波段同时记录下多于一个“群”的振荡,并观察到输出频率的跳变,从实验上证实了“群集效应”。     

Multimode pumping of optical parametric oscillators

Calculations suggest that optical parametric oscillators (OPO's) can be efficiently pumped using multimode, divergent pump sources. The influence of pump beam divergence and mode structure upon OPO performance is measured for both noncritical phase-matching, and OPO's with walkoff. Multimode OPO pumping is shown to be efficient, provided appropriate nonlinear crystals and OPO cavities are employed; the nonlinear crystal must have sufficient angular acceptance to tolerate a divergent pump; the OPO cavity must support modes that match the divergence and spatial intensity characteristics of the pump, For low-order pump modes, the OPO can be made to match the mode of the pump. Higher order pump modes reduce the OPO efficiency, and cause a saturation of efficiency with increasing pump power. The efficiency is degraded in a similar fashion in the presence of walkoff. Multimode pumping is more difficult in longer OPO cavities due to increased buildup time of higher order OPO modes     

纳秒光参量振荡器的综述

结合最新纳秒光参量振荡器(OPOs)的相关文献对纳秒级光参量振荡器的工作特性进行了细致描述,就光参量振荡器的几个重要指标分别进行了探讨,给出了几种新型非线性光学晶体的技术参数,并讨论了其相应的优缺点,最后阐述了纳秒光参量振荡器可能的发展前景。     

Backward optical parametric oscillators and amplifiers

Degenerate backward optical parametric oscillators and amplifiers have been considered, for the first time, to the best of our knowledge. When the pump intensity is four times the threshold pump intensity, the conversion efficiency reaches a maximum value. On the other hand, for nondegenerate optical parametric oscillators, the conversion efficiency always increases as the pump intensity increases. This behavior is different from those for forward optical parametric oscillators. In either configuration, the oscillation can occur without an external feedback. There is, however, a distributed feedback provided through the opposite propagation directions of the signal and idler. The threshold pump intensities for the oscillators can be achieved by the lasers currently available based on quasi-phase matching in several structures. As the input intensity for the backward parametric wave increases, the gain for this wave decreases dramatically if the pump intensity is on the order of the threshold or higher. When the input intensity is much larger than the threshold pump intensity, there is almost no gain regardless of the level of the pump intensity     

Plane-wave theory of self-doubling optical parametric oscillators

This paper presents a theoretical analysis of self-doubling optical parametric oscillators (OPOs) where a single nonlinear crystal is used for both parametric generation and frequency doubling. In these devices, the parametric generation and frequency-doubling processes are both phase matched for the same direction of propagation inside the crystal. Different polarization geometries for which this simultaneous phase-matching condition can potentially be satisfied are identified and categorized. Plane-wave coupled-mode equations are presented for each of these categories. Numerical solutions of these coupled-mode equations and calculation of the single-pass saturated signal gain are outlined. Intracavity signal photon flux calculations based on these numerical solutions are presented. The dependence of performance measures such as the photon conversion efficiency on various design parameters are investigated     

1.57μm内腔光学参量振荡器研究

对内腔光学参量振荡器的工作机理进行了简要分析 ,报道了一种高效、紧凑的 1.5 7μm人眼安全内腔光学参量振荡器的实验结果。它的泵浦源为水冷闪光灯泵浦KD P电光调Q (Ce ,Nd) :YAG激光器 ,采用KTPⅡ类非临界相位匹配 ,输出信号光脉冲能量最高达 87.7mJ ,脉宽约7ns ,重复频率为 10Hz ,总电光效率最高达 5 .8‰ ,器件外形尺寸为 4 10mm× 130mm× 80mm。     

全固态人眼安全OPO激光器

简要介绍一种结构紧凑、高效的全固态1.57μm人眼安全OPO激光器,采用准连续激光二极管(QCW)泵浦的Nd:YAG激光器作泵浦源,OPO为内腔单谐振方式,1.57μmOPO输出能量15mJ/pulse,脉宽～7ns,重复频率20Hz,电光效率2.6%。     

泵浦抽空状态下的同步泵浦光学参量振荡器

用计算机数字模拟了Nd:YAG锁模激光器倍频光同步泵浦下LiNbO_3光学参量振荡器的脉冲形成过程。泵浦抽空状态下,输出信号脉冲序列中各脉冲的波形与宽度各不相同,起始脉冲窄(～7微微秒),后面脉冲宽(～20微微秒)而且有亚结构。腔长失谐主要降低输出能量,对脉冲加宽作用不大。器件增益对脉冲波形、宽度和腔长失谐量均有影响。     

中红外PPMgLN光参变振荡器技术研究

为了实现3.8μm激光输出,采用了1.064μm激光抽运周期性极化掺氧化镁铌酸锂晶体（MgO掺杂摩尔分数为0.05）的光参变振荡器技术,由理论分析得到1.064μm激光抽运PPMgLN实现激光输出时,输出波长与极化周期以及温度的关系曲线。实验中,当晶体周期为29.2μm、温度为400K时,实现了3.8μm激光输出;当抽运功率为35W、声光调Q频率为8kHz条件下,获得3.84μm激光输出的平均功率为3.9W,其转换效率为11.14%,激光光束质量为6.46。结果表明,该技术可以获得较高转换效率的3.8μm激光输出,有望成为中红外激光对抗的激光干扰源。     

Magnetic tunability of fiber optical parametric oscillators with optical clock extraction

A 10 Gb/s all-optical clock extraction based on magnetically controllable fiber optical parametric oscillator (MC-FOPO) is demonstrated.The operation properties of the magnetic control unit,composed of a solenoid and a magneto-optic crystal of high Verdet constant,are experimentally investigated.By adjusting the drive current of the solenoid,the magneto-optic crystal unit may serve as a tunable optical fiber delay line with polarization control to some extent.The experimental results show that the MC-FOPO is capable of repetitively magnetic tunability desirable for all-optical clock recovery.     

人眼安全光学参量振荡器最佳泵浦脉宽

本文讨论了对于人眼安全KTP光学参量振荡器存在一个最佳泵浦脉宽，此时OPO阈值的变化最小，尤其是对于剩余泵浦光被安全反射回去的单谐振OPO。当泵浦脉宽与最佳泵浦脉宽相近时，所需泵浦脉冲能量最小。这对设计小型低阈值OPO器件有极大的指导意义。     

Improvement of optical parametric oscillators by nonresonant pump reflection

Several important characteristics of optical parametric oscillators can be substantially improved by nonresonantly reflecting the pump wave back upon itself after it has passed through the nonlinear medium. Benefits are reduced thresholds, decreased buildup times, and improved efficiencies. Steady-state analyses of doubly and singly resonant oscillators are presented.     

Theory of internal upconversion and frequency doubling in optical parametric oscillators

A uniform plane-wave theory of the type previously employed for the optical parametric oscillator (OPO) is extended to include internal upconversion and frequency doubling. All the experimental configurations for internal upconversion and doubling in the three basic OPO types are treated. Generated intensities are calculated for representative system parameters, and both design parameters and quantum upconversion and doubling efficiencies are obtained for optimum operation in each configuration. The position of the upconverter in the OPO cavity relative to the oscillator crystal and input-pump direction is shown to affect efficiency and output characteristics drastically. The detrimental effects of internal up-conversion on threshold are shown to be an important design consideration. Applicability of the results to pulsed OPO internal upconversion and frequency doubling is determined, and design criteria for selecting the best mode of operation are discussed.     

Some effects of spatially nonuniform pumping in pulsed optical parametric oscillators

Previous analyses of the large signal operation of optical parametric oscillators have considered uniform plane-wave pump beams. These analyses are not adequate to describe the behavior of efficient pulsed oscillators pumped by beams having nonuniform intensity profiles and pulse durations that are short enough that the steady-state transverse modes of the oscillator cavity do not become established. This situation is typical of oscillators with plane-parallel cavities pumped byQ-switched lasers. This paper theoretically and experimentally investigates the behavior of such oscillators when pumped with beams having Gaussian intensity profiles. Each of the three basic external optical parametric oscillators are considered. For simplified cases it is shown that the response to a Gaussian pump beam is quantitatively and qualitatively much different than that predicted by the uniform plane-wave calculations. Experimental results in fair agreement with these calculations are presented. More importantly, uniform plane-wave behavior was observed by using an aperture to probe a small section of the pump beam transmitted through the oscillator. This useful technique gives a sensitive indication of the oscillator operation and, at present, it is the most accurate means of measuring thresholds in pulsed oscillators. As a result of our calculations and experiments, previous experimental observations that were puzzling are now well understood.     

Optical parametric oscillators

Recent developments in β-barium borate (BBO), lithium triborate (LBO), and potassium titanyl phosphate (KTP) optical parametric oscillators are reviewed. It is noted that, with suitable nonlinear optical crystals and pump sources, virtually any wavelength ranging from the UV to the mid IR can now be reached with optical parametric oscillators. The technology is better developed at the present time for the near-UV to 4.5 μm range, however, largely due to the availability of large, high-quality BBO, LBO, MgO:LiNbO₃, and KTP crystals. For the 1-10 μm range, AgGaS₂ and AgGaSe ₂ show great promise