Theory of optical parametric oscillation internal to the laser cavity

Since the fields inside a laser cavity are much higher than the external fields, an analysis of a parametric oscillator with the nonlinear crystal internal to the laser is performed. Using self-consistency equations as the starting point, the equations of motion of such an oscillator are derived. Depending on various cavity, pumping, and nonlinearity parameters, these lead to several types of oscillation with distinctly different operating characteristics: (1) efficient parametric oscillation similar to that of previous analyses; (2) inefficient parametric oscillation resulting from the fact that the nonlinear interaction drives the phases rather than the amplitudes of the signal, idler, and pump; and (3) a pulsing output from the oscillator with repetitive pulses of the signal and idler. A stability analysis of these various regions shows that they are mutually exclusive and can be experimentally chosen by changing the laser gain, the oscillator output coupling, or the strength of the nonlinear interaction. It is shown that the internal oscillator efficiency rapidly approaches the Manley-Rowe limit, as the available pump power becomes several times greater than that required for threshold. The efficiency of an external oscillator having a triply resonant optical cavity is found to be generally less than that of the corresponding internal oscillator.     

信号光脉冲比抽运光窄12倍的内腔式KTP光参量振荡器

在闪光灯抽运的非稳腔Nd∶YAG被动调Q激光器腔内,放置非临界相位匹配KTP晶体,构成内腔式单谐振KTP光参量振荡器(OPO)。研究了输出信号光的波长调谐性能,获得1.57~1.60μm可调谐激光脉冲。实验结果表明,1.57μm信号光的输出能量随着光参量振荡器腔长的增加而减少,脉冲宽度随着腔长的增加而有所变化;抽运能量较大时,转换效率随着抽运能量的增加趋于饱和然后逐渐下降;对此给予了合理的理论解释。当光参量振荡器的腔长为5 cm,1.06μm抽运光脉冲宽度为30 ns时,输出的1.57μm信号光的脉冲宽度为2.5 ns,能量为21.3 mJ。1.57μm信号光的脉冲宽度仅为1.06μm抽运光脉冲的1/12,总的电光能量转换效率为0.128%。     

Short-pulse oscillator development for the Nd:glass laser-fusion systems

This paper describes the development of an actively mode-locked andQ-switched (AMQ) Nd:YAG oscillator system that generates a single pulse at 1.06 μm in the range of 100 ps to 1 ns, with energy ofsim 250 muJ, and with good stability and reliability. A stable single axial modeQ-switched oscillator is also described that generates a long smooth pulse out of which pulses in the ns range are sliced. Synchronization of these two oscillators is also discussed.     

Pulsed Ho:YAG oscillator and amplifier

A pulsed Ho:YAG system has been investigated both as an oscillator and an amplifier. The oscillator was operated normal mode in the TEM00mode with a slope efficiency of 0.012. WhenQ-switched, the laser produced in excess of 80 mJ per pulse with a pulse length of about 30 ns. The predictions of pulse length and energy are in fair agreement with a simple theory presented within. The Ho:YAG was also operated as an amplifier. Large signal gains in excess of 2.0 were observed, which is closely comparable with theoretical predictions. Mode-locked pulses, with a pulse length of about 0.57 ns, were produced by using an acoustooptic mode locker.     

窄线宽1064 nm掺镱光纤激光器泵浦MgO:PPLN中红外光学参量振荡器研究

提出了一种基于1064 nm掺镱光纤激光器泵浦MgO:PPLN的3.83 μm中红外光学参量振荡器。基于单谐振光学参量振荡器的阈值理论和线宽压窄前后的光束能量集中性理论,分析了不同泵浦光束聚焦深度下,谐振腔内光束分布情况以及线宽调制前后能量的不同集中程度对阈值和光-光转换效率所产生的影响。通过采用单个光纤布拉格光栅的方式压窄了泵浦光线宽,对比分析了在不同占空比下,泵浦光线宽压窄前后对中红外光学参量振荡器输出特性的影响。当泵浦功率为18 W,脉冲激光占空比为0.2%,脉宽为100 ns,泵浦光线宽为2.5 nm时,MgO:PPLN中红外光学参量振荡器获得功率为1.42 W的3.83 μm激光输出,光-光转换效率为7.9%。将线宽压窄到0.1 nm后,脉宽为2 ns,MgO:PPLN中红外光学参量振荡器获得最高功率为1.98 W的3.83 μm激光输出,光-光转换效率为11%,光束质量M2=1.89;同时相比于线宽压窄前激光输出效率提高了39.2%。     

高重频人眼安全光参变振荡器实验研究

介绍了连续激光二极管抽运声光Q开关Nd:YAG激光器抽运的高重复频率1.57μm人眼安全光参变振荡器实验研究结果.采用连续激光二极管三侧面抽运Nd:YAG模块和QSGSU-6型小型声光Q开关,1.57μm光参变振荡谐振腔置于1.06μm Nd:YAG激光谐振腔内,非线性晶体为X切割的KTP晶体,利用Ⅱ类非临界相位匹配光参变振荡输出1.57μm波长激光.在重频1kHz~5 kHz时进行了初步实验,在重频3kHz时,获得1.57μm高重复频率激光最大输出功率480mW,最大峰值功率58.8kW,脉宽2.72ns,电光效率达2.6‰.试验结果表明,连续激光二极管抽运声光Q开关内腔光参变振荡器是获得高频人眼安全激光的一种有效途径.     

Mode-locked operation of a Nd:YLF laser and amplification in aQ-switched Nd:glass slab laser

A Nd:YLF laser pumped with a CW dye laser and acoustooptically mode locked at 38 MHz has an output power of 130 mW and a pulse length of 60 ps. Insertion of intracavity etalons and misaligning the mode locker allows for stable operation with a continuous range of pulse lengths from 60 ps to 4 ns. The 1.053-μm emission permits amplification of these pulses in a Q-switched Nd:phosphate glass slab laser oscillator up to intensities limited by optical damage     

外腔式KTP光学参量振荡器的实验研究

利用脉冲氙灯抽运的Nd：YAG被动调Q激光器输出的1．06μm激光脉冲泵浦KTP光学参量振荡器,获得脉宽3ns、单脉冲能量30mJ、中心波长1568nm的信号光输出。信号光脉冲宽度（3ns）比抽运光脉冲宽度（12ns）4,得多。实验表明,随着OPO腔长的增加单脉冲输出能量减小,随着抽运光能晕的增加单脉冲输出．能晕增大,...     

种子注入的高峰值功率全固态单频激光器

为了研制光参量振荡器的单频制抽运源，采用偏压反馈的扫描-触发谐振探测技术，设计了种子注入的脉冲重复频率为500Hz的单端抽运键合Nd:YAG的电光调Q单频脉冲激光器，建立了单纵模振荡并进行了理论分析。结果表明，在抽运能量为36.8mJ时，输出单脉冲能量为8.4mJ，光光建模效率为23%，脉冲宽度为6.8ns，光束质量因子M2≈1.3，脉冲峰值功率为1.2MW；利用F-P标准具获得输出激光的干涉图样，经过1h观察，该激光器输出单纵模概率为100%。这一结果对于抽运光参量振荡器的研制是有帮助的。     

光参量振荡器泵浦源的理论研究与优化设计

研究了作为光参量振荡器的泵浦源1064nm声光Q Nd:YAG激光器.从Nd:YAG激光特性出发,介绍了LD端面抽运Nd:YAG调Q固体激光器的特性,对谐振腔结构进行了等效、分析和数值计算,给出了稳腔条件和腔中振荡光斑随腔长的变化曲线.对调Q脉冲形成过程的速率方程进行了数值计算,得到脉冲形状,分析了泵浦光脉冲形状和脉宽对参量振荡信号光的影响.所得结果对产生高质量、宽调谐、高转换效率的光参量振荡器具有一定的指导意义.     

Q-switching of the CO2laser

The laser pulses obtainable from aQ-switched CO2laser are calculated and compared with the results of a number of different techniques of performing theQ-switching. The continuously operating laser is considered first. The transition rates between the molecular vibrational states and their occupations are derived from the measured CW power. The laser tube was 1.9 meters long, had a diameter of 2.4 cm, and used flowing CO2-N2-He gas. For rapidQ-switching, maximum pulses of 4.5 mJ energy and 85 ns half width are predicted. Such pulses were observed with a rotating mirrorQ-switch. However, that technique has a limited pulse repetition rate and experiments on closely spaced pulses are difficult to interpret. A more flexible technique, which allows a much greater variation in the experimental parameters, is the use of a fast shutter to interrupt the laser beam in the cavity. While this switch is somewhat slower than the rotating mirror it does produce pulses of the same energy at repetition rates up to 5000 per second, and smaller pulses at any desired higher rate. From these measurements the upper and lower laser level lifetimes are deduced. They are found to agree well with the values obtained from the CW measurements.     

中红外砷酸钛氧钾光参变振荡器的实验研究

为了得到高能量中红外激光输出,对电光调Q灯抽运1064nm Nd:YAG抽运复合腔砷酸钛氧钾(KTA)光学参变振荡器(OPO)作了实验研究,在工作频率1Hz时得到OPO输出单脉冲能量6mJ,信号光脉宽10ns,闲频光波长407nm,能量11mJ.在5Hz～40Hz范围单脉冲能量随重复频率增高而降低.实验中采用的复合腔抽运技术有利于提高转换效率,降低起振阈值.使用上述光源对中红外成像器件作实验,在成像系统监视器上观察到激光光斑.这一结果对中红外激光器的研究是有帮助的.     

Pulse stretching utilizing two-photon-induced light absorption

The effect of inserting an element exhibiting induced absorption into aQ-switched laser cavity is investigated theoretically and experimentally. The rate equations are solved assuming two types of nonlinear loss, one being proportional to the square of the laser intensity and the other being proportional to the product of laser intensity and density of excited electrons in the nonlinear absorber. Experiments are performed with a rotating-prism ruby laser with a CdS crystal in its cavity. It is established that two-photon absorption takes place, and as predicted by the theory that the output intensity and output energy both decrease and pulse length increases as compared with the normalQ-switched case. In addition, the output pulse has an oscillatory behavior, and it is suggested that this is caused by loss due to the excited electrons, which are found to have a lifetime of approximately 24 ns.     

Internal Q-switching in GaAs junction lasers

InternallyQ-switched light pulses have been obtained from junction lasers. It is believed that this is a completely new observation for semiconductor lasers. Using specially fabricated diodes, narrow bursts of light were detected immediately after the termination of the injection current pulse. The effect persists for a wide variation in the length of the current pulse, from less than 2 ns to several μs. The width of theQ-switched light pulse itself is less than 0.4 ns, this value being the resolution of our detection system. Its energy increases rapidly with the amplitude of the injection current. The occurrence of stimulated emission after the end of the injection pulse indicatesQ-switching due to a reduction of the internal absorption. This reduction allows those injected carriers that have not yet spontaneously recombined to produce the narrow burst of stimulated light. TheQ-switching is observed over a current amplitude range that is a very strong function of temperature. This range can be relatively large. One diode at 150°K showedQ-switching after current pulses from 1.2 to 5.0 amperes; for amplitudes greater than 5.0 amperes, normal stimulated emission occurred during the current pulse. As the temperature is increased, theQ-switched pulse is first observed near Tt, the so-called "transition temperature" where trapping effects first start to cause long delays between the application of the current pulse and the onset of stimulated emission. Therefore, it is believed that the same traps are involved in both the long delays and theQ-switching. The latter is observed only in diodes with low Ttvalues where the absorption due to traps accounts for a large proportion of the total losses of the laser. A model explaining these effects will be presented.     

被动调Q人眼安全内腔光学参量振荡器

利用被动调Q内腔光学参量振荡器动力学模型 ,求解了包含内腔光学参量振荡器的被动调Q速率方程 ,讨论了被动调Q内腔光学参量振荡器的动力学过程。实验上实现了被动调Q内腔光学参量振荡器运转 ,获得了脉宽小于 5ns ,能量大于 2 0mJ的 1 5 7μm人眼安全激光输出 ,通过改变OPO谐振腔输出镜的反射率 ,观测到输出单个和多个信号光脉冲现象 ,实验结果与理论分析相吻合。     

High gain laser performance in alexandrite

Half-jouleQ-switched pulses of 20 ns duration have been obtained from an alexandrite laser operating on the high-gainR-line. Unique tandem pulsing, involving both a fixed and a tunable frequency pulse, is also observed.     

可调谐超短中红外激光脉冲的参变产生与放大及其最新进展

介绍了基于非线性光学参变过程产生和放大中红外可调谐超短激光脉冲的主要方法,比较了参变振荡、差频产生、光学参变放大和啁啾脉冲光学参变放大等4种产生与放大方法的技术特点,重点评述了最近10年来国内外利用光学参变放大和啁啾脉冲光学参变放大实现大增益宽带和高峰值功率输出的最新进展.探讨了获得更高能量/功率和更短脉冲(更大带宽)...     

Subnanosecond laser pulses from a grazing incidence dye laser

Dye laser pulses with a duration of 160-350 ps and a spectral width of 0.06 nm were obtained by pumping a grazing incidence dye laser with aQ-switched Nd : YAG laser. The pulse shortening was due to a cavity transient effect which has also been observed in N2laser-pumped dye lasers.     

An actively mode-locked/Q-switched Nd:phosphate glass laser oscillator

Good stability and reliability is achieved in the operation of a laser oscillator with Nd-doped phosphate glass that is actively mode-locked, as well as activelyQ-switched. It delivers a single pulse at 1.053 μm with an energy of 140μJ. Pulse duration is variable between 150 ps and 1.1 ns. The system offers a TTL trigger well related to the Single pulse.     

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。