Simulation of laser dynamics and active Q-switching in Tm,Ho : YAG and Tm : YAG lasers

 We developed a detailed rate equation model to study laser dynamics and active Q-switching in Tm,Ho: YAG and Tm:YAG lasers. The simulation results agreed well with published experimental data, as well as provided new insights for optimizing pulse generation. Received: 7 March 1996/Accepted: 28 May 1996     

Cr,Tm,Ho∶YAG激光器的理论模拟

为了使CTH∶YAG激光器的设计得到更好的优化，从晶体光谱吸收特性、离子间能量转移过程及准三能级运转方式对CTH∶YAG激光器的工作特性进行了理论分析；依据速率方程理论建立了CTH∶YAG激光器运转的理论模型.模拟能量输出与试验结果较好的吻合，验证了此理论模型描述CTH∶YAG激光器运转规律的合理性.模拟结果表明：CTH∶YAG激光器的激光脉冲输出与泵浦有较长的时间延迟且伴随较强的驰豫振荡，冷却温度对激光输出产生较大的影响.     

Cr,Tm,Ho∶YAG激光器的理论模拟

为了使CTH∶YAG激光器的设计得到更好的优化,从晶体光谱吸收特性、离子间能量转移过程及准三能级运转方式对CTH∶YAG激光器的工作特性进行了理论分析;依据速率方程理论建立了CTH∶YAG激光器运转的理论模型.模拟能量输出与试验结果较好的吻合,验证了此理论模型描述CTH∶YAG激光器运转规律的合理性.模拟结果表明:CTH∶YAG激光器的激光脉冲输出与泵浦有较长的时间延迟且伴随较强的驰豫振荡,冷却温度对激光输出产生较大的影响.     

Diode-pumped tunable single-longitudinal-mode Tm,Ho:YAG twisted-mode laser

A diode-end-pumped tunable twisted-mode cavity Tm, Ho:YAG laser with single-longitudinal-mode(SLM)operation is demonstrated in this Letter. The maximal SLM output power is 106 m W with a slope efficiency of 4.86%. The wavelength can be changed from 2090.38 to 2097.32 nm by tuning the angle of an etalon.     

A 20 W Cr, Tm, Ho: YAG laser

A 2.1 μm Cr³⁺, Tm³⁺, Ho³⁺ : YAG laser is operated with an output power of 20 W at 12 Hz. The laser output is successfully transmitted through a silica fibre. The laser system was designed based on the technology of an alexandrite laser oscillator.     

Single-frequency, Q-switched Ho:YAG laser at room temperature injection-seeded by two F-P etalons-restricted Tm, Ho:YAG laser

We demonstrated a 1.91 μm pumped, injection-seeded Q-switched Ho:YAG laser operating at room temperature. By inserting two Fabry-Perot etalons into the laser cavity, single-frequency Tm, Ho:YAG seed lasing was achieved at a wavelength of 2090.9 nm, with a typical output power of 60 mW. Single-frequency, nearly transform-limited Q-switched operation of the Ho:YAG laser was achieved by injection seeding. The output energy of the single-frequency Q-switched pulse is 7.6 mJ, with a pulse width of 132 ns and a repetition rate of 100 Hz. We measured the pulse spectrum, half-width of which was 3.5 MHz, by a heterodyne technique.     

高功率Cr,Tm,Ho:YAG激光器的实验研究

在医学应用上,Cr,Tm,HoYAG激光器需要在大功率、高重频下工作.合理的设计对提高Cr,Tm,HoYAG激光器的输出功率是很重要的.通过对Cr,Tm,HoYAG输出特性进行理论分析和实验验证可知,腔长、全反射镜曲率半径、输出镜透过率、水温等因素对Cr,Tm,HoYAG激光器的输出功率均有影响.提出了优化设计Cr,Tm,HoYAG激光器的方法.在镀银腔情况下,当重频为10Hz时,激光阈值为45J,斜效率为1.1%;当输入能量为121J时,输出的平均功率为9.7W.在陶瓷聚光腔情况下,当重频为10Hz时,激光阈值为40J,斜效率为2.7%;当输入能量为100J时,输出的平均功率为16.2W.     

520 mJ langasite electro-optically Q-switched Cr, Tm, Ho:YAG laser

A flash lamp pumped 2.09 μm Cr, Tm, Ho:YAG laser utilizing a self-grown La(3)Ga(5)SiO(14) crystal as the electro-optic Q-switch generator is proposed and demonstrated for the first time. Operating at 3 Hz repetition rate, 520 mJ pulse energy with 35 ns pulse width is achieved by optimizing the Q-switch delay time and compensating for the thermal depolarization with a quarter-wave plate. The corresponding peak power is 14.86 MW, and the Q-switched-to-normal-mode energy extraction efficiency is 66.3%. To our knowledge, this Q-switched giant pulse is the best result reported to date in 2.09 μm laser resonator.     

Graphene passively Q-switched Ho:YAG ceramic laser

We report on the first graphene passively Q-switched Ho:YAG ceramic laser with central wavelength of 2,097 nm. Stable pulses of 28–64 kHz repetition rate and 2.6–9 μs pulse widths were generated under 1,907 nm thulium fiber laser pumping. Maximum average power of 264 mW with 9.3 μJ pulse energy was obtained under 3.27 W of pump power.     

Thermal Behavior of the Fluorescence Lines of Ho3+ in Cr,Tm,Ho:YAG

The fluorescence spectra of Cr,Tm,Ho∶YAG crystal have been detected at the temperature from 65 to 295 K with interval of 10 K.The width and the shift of Ho3+ lines at 4959.6 cm-1 (at 65 K) have been investigated and interpreted in terms of the interactions between lattice vibration (phonons) and ions.The results showed that the line broadening with the temperature was mainly due to the Raman scattering of phonons,and the line shift with temperature was mainly due to the emission and absorption of virtual phonons.     

Fabrication and properties of tape-casting transparent Ho:Y_3Al_5O_(12) ceramic

High-quality holmium-doped Y3Al5O12(YAG) ceramic is fabricated in sequence by tape-casting and vacuum sintering. The average grain size of the Ho:YAG ceramic is around 20 μm with a fully dense microstructure. The inline transmittance of the sample is ～82% in visible and IR region. The fluorescence lifetime at 2088 nm is8.17 ms. The excellent properties of the Ho:YAG ceramic demonstrate the tape-casting is a novel candidate process for the fabrication of Ho:YAG-based thin-chip or composite ceramics.     

Continuous-wave operation of a room-temperature Tm: YAP-pumped Ho: YAG laser

We report a continuous-wave (CW) 2.1-μm Ho:YAG laser operating at room temperature pumped by a diode-pumped 1.94-?m Tm:YAP laser.The maximum output power of 1.5 W is obtained from Ho:YAG laser,corresponding to Tm-to-Ho slope efficiency of 17.9% and diode-to-He conversion efficiency of 5.6%.     

2-W Ho:YAG laser intracavity pumped by a diode-pumped Tm:YAG laser

Efficient room-temperature operation of a Ho:YAG laser, intracavity pumped by a diode-bar-pumped Tm:YAG laser, is reported. At rod mount temperatures of 10 degrees C, for both the Tm:YAG and the Ho:YAG rods, we obtained 2.1 W of output at 2.097mum from the Ho:YAG laser for 9.2 W of diode power incident upon the Tm:YAG rod.     

高功率Cr,Tm,Ho∶YAG激光器的实验研究

在医学应用上,Cr,Tm,Ho∶YAG激光器需要在大功率、高重频下工作。合理的设计对提高Cr,Tm,Ho∶YAG激光器的输出功率是很重要的。通过对Cr,Tm,Ho∶YAG输出特性进行理论分析和实验验证可知,腔长、全反射镜曲率半径、输出镜透过率、水温等因素对Cr,Tm,Ho∶YAG激光器的输出功率均有影响。提出了优化设计Cr,Tm,Ho∶YAG激光器的方法。在镀银腔情况下,当重频为10Hz时,激光阈值为45J,斜效率为1.1%;当输入能量为121J时,输出的平均功率为9.7W。在陶瓷聚光腔情况下,当重频为10Hz时,激光阈值为40J,斜效率为2.7%;当输入能量为100J时,输出的平均功率为16.2W。     

Tunable single-longitudinal-mode operation of a sandwich-type YAG/Ho:YAG/YAG ceramic laser

We present a 2.09 μm single-longitudinal-mode sandwich-type YAG/Ho:YAG/YAG ceramic laser pumped by a Tm-doped fiber laser for the first time. A pair of F-P etalons was used to achieve tunable single-longitudinal-mode operation. The maximum single-longitudinal-mode output power of 530 mW at 2091.4 nm was obtained with an absorbed pump power of 8.06 W, corresponding to an optical conversion efficiency of 6.6% and a slope efficiency of 12.7%. Wavelength tunable was achieved by tuning the angle of etalons and the wavelength could be tuned from 2091.1 nm to 2092.1 nm, corresponding to a tuning frequency of 68 GHz. The M² factor was measured to be 1.23.     

LD抽运Cr,Tm,Ho:YAG微片激光器单纵模运转特性的研究

研究了LD抽运的单纵模Cr,Tm,Ho:YAG微片激光器,激光器厚度为1mm,在用波长785nm的LD进行端面抽运时,激光器阈值为1060mW,单纵模激光最大输出功率为31mW. 对激光器输出功率随温度变化特性进行了研究,验证了CTH:YAG晶体的温度敏感性. 还研究了激光器的温度调谐特性,实验测得激光器的温度调谐系数为1.4GHz/℃.     

Thermal-lens measurement of a quasi steady-state repetitively flashlamp-pumped Cr, Tm, Ho:YAG laser

A simple technique using cavity stability conditions is demonstrated to measure the effective dynamic thermal lensing of a flashlamp-pumped Cr, Tm, Ho:YAG laser operated in a low repetition-rate regime of 4–7 Hz. By measuring the flashlamp energy where a stable resonator becomes unstable, the effective focal length of the laser rod can be calculated. When no mode restricting aperture is used in the cavity, the thermal lens behaviour displays a significant deviation from the commonly assumed thin lens approximation.     

Ho:YAG laser intracavity pumped by a diode-pumped Tm:YLF laser

We report a compact Ho:YAG laser that is intracavity pumped by a diode-pumped Tm:YLF laser. Both lasers exhibit pulse mode behavior. Operating both crystals at room temperature (25 degrees C), we obtained 1.6 W of average output at 2.09 microm from the Ho:YAG laser for 15.4 W of diode power incident upon the Tm:YLF rod and a slope efficiency of 21%.     

Spectroscopic characteristics of YSGG:Cr,Ho, YSGG:Cr, Tm and YSGG:Cr,Tm,Ho

In this paper some spectroscopic properties of Y₃Sc₂Ga₃O₁₂ (YSGG):Cr,Ho, YSGG:Cr,Tm and YSGG:Cr,Tm,Ho are presented. The three lowest energetic manifolds of Ho³⁺ and Tm³⁺ in YSGG have been determined at 10 K. Time-resolved fluorescence build-up and decay of the laser active ions was measured in three crystals with different dopant concentrations. The transitions investigated were⁵I₇ ⁵I₈ for Ho³⁺ near 2000 nm and³H₄ ³H₆ for Tm³⁺ near 1800 nm. The data found on time-resolved fluorescence and energy level positions are useful for the discussion of the energy transfer characteristics of the system.     

Efficient High-Power Ho:YAG Laser Pumped by Dual-End-Diode-Pumped Tm:YLF Laser

We report a Ho:YAG (Ho-doped yttrium aluminum garnet) laser pumped by a dual-end-diode-pumped Tm:YLF (Tm-doped yttrium lithium fluoride) laser to obtain an efficient experimental device with high output-power characteristics. We study the influence of the specific values of the output coupling mirror transmittance, the resonant cavity length, and the radius of curvature of the output coupling mirror on the Ho:YAG laser output characteristics. Under optimum experimental conditions, under which the output coupling mirror transmittance was 30%, the resonant cavity length was 25 mm and the output coupling mirror radius of curvature was 300 mm, and the maximum pumping power of the dual-end-diode-pumped Tm:YLF laser was 15.2 W. We obtain an efficient high-power 2.122-μm laser output of 7.98 W from the Ho:YAG laser. The optical-to-optical conversion efficiency is 52.5%, and the beam quality factor figures are M _x ² ?=?2.89 and M _y ² ?=?2.97.