钕玻璃激光器热容方式运行的能量特性研究

钕玻璃激光器采用双灯对称紧耦合非聚焦泵浦腔,先后以热容及常规水冷方式运行10 s（重复频率10 Hz）,分别记录100个光脉冲的脉冲能量.通过对比实验分析脉冲能量变化趋势,热容方式运行的钕玻璃激光器的平均输出功率及单脉冲能量均高于常规运行方式,约为1.4倍.结合理论计算,验证了热容激光器在抽运阶段输出的全部脉冲串能量的理论值.该结果对进一步了解钕玻璃激光器热容运行方式的输出特性具有一定的参考价值.     

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     

Passively Q-switched Nd:glass fibre-bundle laser

The performance of a flashlamp-pumped fibre-bundle laser passively Q-switched by a Cr⁴⁺:YAG crystal is reported. Simultaneous passive Q-switching of 250 highly Nd-doped multimode phosphate glass fibres delivers pulses with 35 ns duration at a rate of 20 kHz. The generated Q-switch pulses are strongly modulated by a train of pulses <500 ps with high peak powers exceeding 1 MW     

转动玻璃圆筒激光器

本文介绍了转动玻璃圆筒激光器的设计及实验结果,得到了脉冲能量为13J,重复频率为15Hz的激光输出。电光转换效率为2.2％,斜效率为3.4％。     

CW laser operation of Nd:YLF

CW laser operation of Nd:YLF is reported for the first time and, in a comparison to Nd:YAG, exhibits a lower threshold and higher single-mode average power. The TEM00mode volume of Nd: YLF was observed to be a factor of four larger than Nd:YAG, resulting in twice the TEM00mode average power. This result is attributed to the substantially lower thermal lensing of YLF with respect to YAG. In comparative measurements the stimulated emission cross section of Nd:YLF was found to be1.8 times 10^{-19}cm²for the π oscillation and1.2 times 10^{-19}cm²for the σ oscillation, as compared to2.4 times 10^{-19}cm²for Nd:YAG. The spectroscopic and lasing parameters of Nd:YLF indicate a potential for this material in high peak and average powerQ-switched applications.     

Continuous wave thin plate Nd:glass laser

CW (continuous-wave) operation of end-pumped four-level glass lasers is modeled to obtain expressions for threshold, slope efficiency, and figures of merit. The thermal effects ultimately limiting performance in these lasers is also discussed. Basic design consideration for optimum performance of an end-pumped CW Nd:glass laser intended for mode locking are presented. On the basis of these investigations, a CW Nd:glass laser containing a heavily doped thin phosphate glass plate as the gain material has been built. The plate was inserted into a folded cavity and pumped longitudinally by a Kr laser at 0.8 μm. With 2.5% output coupling the pump threshold and the slope efficiency well above threshold were measured to be 10.5 mW and 36%, respectively. These values agree reasonably with theoretical predictions. Experimental confirmation of the predicted thermal limiting effects are also obtained     

FM-laser operation of the Nd:YAG laser

The FM-laser or frequency-sweeping mode of laser oscillation has been demonstrated in a Nd :YAG 1.06-μ laser with an intracavity LiNbO3phase modulator. The experimental results are in excellent agreement with the theoretical expressionDelta= (DeltaOmega/Deltanu) (delta/pi)where δ= peak single-pass phase retardation in the modulator,DeltaOmega= axial mode spacing,Deltanu=modulator detuning, and Δ=resulting FM index of the laser output. Modulation indices as large asDelta approx 230rad have been obtained, in which case the instantaneous laser frequency is sweeping over a full spectral range of2Delta cdot f_{m} approx 120GHz (≈ 4 cm^-1) at a repetition frequencyf_{m} approx 260MHz, with a time-bandwidth product per periodapprox 2Delta approx 460. The coherently mode-locked spectral bandwidth thus obtained in the FM-laser case is very much wider than can be achieved in the pulsed mode-locked case with the same Nd:YAG laser. Some possible ways of using this broad-band coherent FM spectrum are suggested.     

Spectroscopy and lasing of a high Nd concentration Al-phosphate glass

An Al-phosphate glass containing Nd³⁺in concentrations ranging from3 times 10^{20}to2.7 times 10^{21}ions/cm³has been prepared and investigated spectroscopically. Different ways of measuring the⁴F3/2→⁴I9/2emission cross sections yield values between1.96 times 10^{-20}and2.7 times 10^{-20}cm². At the highest concentration the decay time is 50 μs, while the radiative lifetime is estimated to begeq446 mus. Lasing experiments were performed by pumping thin platelets of glass coaxially with a dye laser. Cross sections, losses, and differential efficiencies are derived from these experiments. The status of high concentration glasses versus stoichiometric Nd compounds is reviewed.     

高指向稳定性的钕玻璃调Q激光器

本文讨论了激光束指向稳定性的重要意义,报导了调Q钕玻璃激光振荡器的指向稳定性优于20″/20天.     

Feedback stabilized actively mode-locked Nd:phosphate glass laser

An electrooptic, actively mode-locked Nd: phosphate glass laser system is described employing a novel single-step feedback system to stabilize the pulse buildup time. Single output pulses of ∼100 ps duration with energies of up to 1 mJ could be reliably generated with a standard deviation in thesim3.2 mus pulse buildup time of ±40 ns allowing synchronization with pulses from laser systems at other wavelengths. Evidence of pulse broading due to self-phase modulation was observed together with wide tunability of the output wavelength from 1.054 to 1.068 μm.     

Compact, single-frequency, high-power Nd: glass laser

A compact, single-frequency high-power Nd:glass laser was developed. Single longitudinal mode operation of the oscillator was provided by injection-seeding it with CW laser radiation. A four-pass amplifier with a spatial filter provided an output energy of 2.7 J with more than 30% extraction efficiency. The output beam divergency was twice the diffraction limit     

Static gas conduction cooled slab geometry Nd:glass laser

We report on the first demonstration of a 10 Hz static gas cooled slab geometry Nd:glass laser. This cooling approach provides thermal control of the slab laser medium while eliminating mounting and optical problems associated with liquid cooling.     

Single-frequency operation of diode-laser-array transverse-pumped Q-switched Nd:YAG laser

Single-longitudinal-mode and single-transverse-mode operation of a miniature Nd:YAG laser transversely pumped by a quasi-CW diode-laser array is described. By injection-seeding this oscillator with a diode-laser end-pumped Nd:YAG microlaser, single-frequency Q-switched pulses of 0.25 mJ energy and 35 ns duration were generated.<>     

Output beam focusability of a Nd:glass zig-zag slab laser

The focusability of a zig-zag optical path laser with a 230×65×5 mm Nd:glass for application to soft X-ray generation is described. A Q-switched laser output energy of 18.3 J with a pulse width of 28 ns was obtained in a phosphate glass LHG-5 (Nd:8 wt.%), with an extraction efficiency of 71% from a stored energy of 26 J at a pumping energy of 4 kJ. The focusability was achieved up to 6.2×10¹² W/cm² in a spot size of 100 μm, which was sufficient intensity to generate soft X-rays for X-ray lithography     

二极管角部抽运Nd:YAG基模激光器

为了分析角部抽运方式在中小功率激光器设计中的可行性,基于光线追迹法,计算了不同的激光介质几何结构参量和不同的二极管温度条件下角部抽运复合板条激光器的抽运效率和抽运均匀性。从模拟计算结果可知,只要选择合理的激光介质结构参量,角抽运方式能得到高的抽运效率和较好的抽运均匀性。设计了一种角部抽运Nd:YAG复合板条激光器,在45W的抽运功率下获得了12W的激光输出,光光转换效率约为26.7%,在40W抽运时光束质量Mx2=1.47,My2=1.36。理论分析和实验设计表明,角抽运方式在小功率激光器设计中是可行的。     

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.     

扭动光束钕玻璃棒状激光放大器

利用扭动入射激光束抑制在钕玻璃内部产生的热自聚焦效应。在5～10毫秒脉宽范围内,钕玻璃的破坏阈值提高了一倍以上,同时大幅度地提高了光束亮度。建立了两种扭动光束的复元机构。     

Controlled bistable operation of an FM mode-locked Nd:YAG laser

It is well known that there are two possible phase positions for the pulse in a mode-locked laser with an internal phase modulator. By using a modulator cut in the form of a Brewster angle prism, it becomes possible to operate an Nd:YAG laser stably in either position at will. The angular beam deflection is slightly different for the two modes and, hence, by mirror adjustment one mode or the other can be selected. A simple analysis is presented to estimate the magnitude of this effect in rough agreement with experimental observations.     

Actively initiated quasi-passive mode-locking in a CW SELFOC Nd:glass laser

Actively initiated quasi-passive mode-locking has been achieved in a small-power CW SELFOC Nd:glass laser. Three means have been taken to enhance the pulse intensity incident on a saturable dye to a magnitude sufficient for nonlinear absorption initiation: 1) tight focusing, 2) controlled spiking oscillation, and 3) auxiliary active mode-locking. Mode-locked pulses having an 11-12-ps pulsewidth were obtained. Interpretation concerning the observed mode-locked-pulse intensity-correlation curves is presented. To obtain satellite-pulse-free mode-locked pulses, a modified mode-locking process with sufficiently long buildup time is considered.     

Modeling and CW operation of a quasi-three-level 946 nm Nd: YAG laser

A model is developed for an end-pumped quasi-three-level laser with population in the lower laser level at equilibrium such as for transitions to the manifolds⁴I9/2in Nd³⁺,⁴I15/2in Er³⁺,⁵I8in Ho³⁺and³H6in Tm³⁺. It is shown that the effect of residual lower laser level population on laser operation can be treated as a saturable loss. Room temperature operation on the⁴F3/2-⁴I9/2transition in Nd:YAG under CW dye laser pumping has been demonstrated with a threshold as low as 11.5 mW incident power and a slope efficiency of 7 percent with 0.3 percent output coupling. Performance is limited by the low output coupling and diffraction loss.