2041.3 nm/2054.6 nm simultaneous dual-wavelength single-longitudinal-mode Tm,Ho:YVO<Subscript>4</Subscript> microchip laser

We report a single-longitudinal-mode CW diode-pumped Tm, Ho: YVO₄ microchip laser emitting at both 2041.3 and 2054.6 nm. At each wavelength, the laser has a single longitudinal mode. The total single-longitudinal-mode output power reaches 185 mW with 20.4% optical conversion efficiency at 905 mW incident pump power.     

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 single-longitudinal-mode continuous-wave Ho~(3+):YVO_4 laser at 2.05 μm pumped by a Tm-fibre laser

We present a single-longitudinal-mode continuous-wave Ho~(3+):YVO_4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho:YVO_4 laser is suitable for use as a seed laser in some Lidar systems(e.g., coherent Lidar or differential absorption Lidar). To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho:YVO_4 laser at 2.05 μm.     

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.     

High power single-longitudinal-mode Ho:YLF unidirectional ring laser based on a composite structure of acousto-optic device and wave plate

We report a unidirectional single-longitudinal-mode Ho:YLF ring laser. An acousto-optic modulator and two half-wave plates were used to enforce the Ho:YLF ring laser in a unidirectional operation. The single-longitudinal-mode output power could reach 3.73 W successfully when the incident pump power was 16.4 W. The corresponding slope efficiency was 27.1%. The wavelength of the single-longitudinal-mode Ho:YLF ring laser was 2063.8 nm. The M² factor was 1.12. The results illustrated that the single-longitudinal-mode output power could be further enhanced by increasing the radio frequency power of the acousto-optic modulator.     

Output performance of thermally-insensitive passively Q-switched Nd:YAG laser

We study a Cr⁴⁺:YAG Q-switched Nd:YAG laser with a thermally-insensitive corner-cube-prism cavity where the corner cube prism is the key element. The corner cube prism is insensitive to misalignment in any direction. We demonstrate experimentally that a laser cavity with such a prism provides stable laser performance under violent changes of ambient temperature and the effect of the laser crystal thermal lens. The laser mode properties are analyzed by numerical simulations. We show that the numerically simulated results agree well with the experimental ones.     

A thermally-insensitive passively Q-switched Cr:YAG/Nd:YAG laser

A passively Q-switched laser with Cr⁴⁺:YAG/Nd:YAG composite crystal using a corner cube prism cavity has been realized, in which the corner cube prism is the key element as it aids the compensation of the thermal lens effect of laser crystal. Compared with plane–plane mirror cavities under the same conditions, the stability of the laser performance using the corner cube prism cavity was improved remarkably over temperatures ranging from −40 to 65 °C. The decrease of Nd:YAG stimulated emission cross section with temperature was considered to be the main reason for the increase of average output pulse energy under the same cycle for the two different cavities when the ambient temperature changed −40 to 65 °C. The mode properties produced by the prism cavity were analyzed, and the theoretical results were verified by experimental observations.     

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%.     

Greatly improved stability of passively Q-switched Ce:Nd:YAG laser by using corner cube prism

In order to solve the hard problem of laser instability, a miniature Cr⁴⁺:YAG Q-switched Ce:Nd:YAG laser with a retroreflecting corner cube prism is demonstrated. The corner cube prism is insensitive to misalignment in any direction. Laser cavity with the prism is found to meet the condition of violent change of environment temperature and the variation of thermal lens of laser crystal by our experiment. Compared with flat-flat cavity, stability of the laser with a retroreflecting corner cube prism is improved remarkably.     

103 W in-band dual-end-pumped Ho:YAG laser

An efficient 2?μm in-band pumped Ho:YAG laser was demonstrated. The resonator involves two Ho:YAG crystals, each of which was dual-end-pumped by two orthogonally polarized diode-pumped Tm:YLF lasers. The maximum continuous wave output power of 103?W was achieved, corresponding to a slope efficiency of 67.8% with respect to the incident pump power and an optical-to-optical conversion efficiency of 63.5%. Under Q-switched mode, we obtained 101?W laser output at 30?kHz, corresponding to a slope efficiency of 66.2%. The beam quality or M² factor was found to be less than 2.     

High-power Er:YAG laser with quasi-top-hat output beam

A simple method for simultaneously exciting the fundamental (TEM00) transverse mode and first order Laguerre-Gaussian (LG01) donut mode in an end-pumped solid-state laser to yield a quasi-top-hat output beam is reported. This approach has been applied to an Er:YAG laser, in-band pumped by an Er,Yb fiber laser, yielding 9.6 W of continuous-wave output at 1645 nm in a top-hat-like beam with beam propagation factor (M2)<2.1 for 24 W of incident pump power at 1532 nm. The corresponding slope efficiency with respect to incident pump power was 49%. The prospects of further scaling of output power and improved overall efficiency are considered.     

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%.     

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1?mm,在用波长785?nm的LD进行端面抽运时,激光器阈值为1060?mW,单纵模激光最大输出功率为31?mW. 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4?GHz/℃. 关键词： 激光光学 CTH∶YAG微片激光器 LD抽运 单纵模运转     

Passively Q-switched Nd3+:YAG laser with corner cube

A passively Q-switched Nd3+:YAG laser with corner cube is theoretically and experimentally studied. We analyze the polarization variation in cavity and simulate the peak power, pulse energy and pulse width changed with the rotation angle of corner cube numerically. An experiment is made to verify the theoretical results. With rotating the angle of corner cube about the axis the variation range of peak power is 1.77 MW (from 10.36 to 8.59 MW), and that of pulse energy is 14.9 mJ (from 159.5 to 174.4 mJ), the fluctuation of pulse width is 2.95 ns. The experimental results agree with the theoretical analysis to the extent of variation rules. The most dynamic to static energy ratio of 62.5% is achieved.     

In-band pumped highly efficient Ho:YAG ceramic laser with 21 W output power at 2097 nm

We report on the high-power and high-efficiency operation of a polycrystalline Ho:YAG ceramic laser in-band pumped by a Tm fiber laser at ~1907 nm. Lasing characteristics of a 1.5 at.% and a 2.0 at.% Ho3?-doped YAG ceramic were investigated and compared. Using an output coupler of 6% transmission, over 21.4 W of cw output power at 2097 nm has been generated with the 1.5 at.% doped Ho:YAG ceramic under 35 W of incident pump power, corresponding to an average slope efficiency with respect to the incident pump power of 63.6% and an optical-to-optical conversion efficiency of 61.1%.     

Room temperature single longitudinal mode Tm,Ho:Yap microchip laser at 2102.6 nm

Room temperature single-longitudinal-mode operation of a c-cut Tm(5%), Ho(0.3%):YAP microchip laser pumped by a fiber-coupled diode-laser is reported. An incident pump power of 3.06 W is used to generate the maximum single-frequency output power of 42 mW at 2102.6 nm, corresponding to optical-to-optical conversion efficiency of 1.4%. To the best of our knowledge, this is the first time to report of Tm,Ho:YAP microchip laser operation on single-frequency at room temperature.     

Diode-pumped single longitudinal mode lasing of Tm,Ho:YLF microchip laser

Short resonant cavity which owns broad free spectral range is useful to select single-frequency. We take Tm,Ho:YLF (Tm 6%; Ho 0.4%) microchip pumped by diode laser to attain high efficiency single-longitudinal-mode laser. Both end faces are coated. The microchip is the oscillate cavity itself. It’s placed in the Dewar flask, which is filled with liquid nitrogen to keep the temperature at 77 K. Comparison of the laser characteristics between a 0.9 mm microchip and a 0.5 mm microchip were expressed in this report. The maximum single-longitudinal-mode power are 33 and 76 mW, corresponding the slope efficiency of both lasers are 12 and 37%, separately. The beam quality is about 1.06 and 6.8 for 0.9 mm microchip and 0.5 mm microchip, measured by the knife-edge method.     

A comparative study on diode-pumped single-frequency Tm:YAG and Tm:GdVO<Subscript>4</Subscript> lasers

In this paper, we present experimental results concerning on the laser characteristics of Tm:YAG laser and Tm: GdVO₄ laser. At room temperature, the maximum output power of Tm:YAG laser and Tm:GdVO₄ laser is 210 and 145 mW, respectively. High efficiency can be achieved for both lasers at room temperature. Nevertheless, compared with Tm:GdVO₄ laser, Tm:YAG laser can operate on single frequency with high power easily. As much as 60 mW of 2013.9 nm single-longitudinal-mode (SLM) laser was achieved for Tm:YAG laser. For Tm:GdVO₄ laser 51 mW of 1919.7 nm SLM laser was achieved. The SLM Tm:YAG laser is better for using as a seed laser for coherent wind measurements and differential absorption LIDAR systems.     

Excellent stability of laser passively Q-switched with a retroreflecting corner cube prism

A miniature Cr⁴⁺:YAG Q-switched, repetitive operation, conductive cooling Nd:YAG laser with a retroreflecting corner cube prism is demonstrated. The corner cube prism which is insensitive to misalignment in any direction makes it useful for the laser to adapt to the violent change of ambient temperature and also makes the laser cavity insensitive to the variation of thermal lens of the crystal. The laser has excellent stability of the average output pulse energy and the threshold voltage under different ambient temperature of −40, 25, and 55°C.     

热透镜控制激光光束质量技术研究

在端面抽运固体激光器中,就如何改善在高抽运功率时输出激光的光束质量,提出一种激光器的设计方法。在激光器谐振腔中放入多根掺杂浓度不同的激光介质,利用激光介质内部产生的热透镜控制抽运光和基模振荡光的空间分布,并且最大限度地使抽运光的分布区和基模振荡光分布区重叠,实现抽运光与基模振荡光在空间上高度匹配,进而提高抽运光能量的利用效率和振荡光的光束质量。实验表明,在不同抽运功率下,抽运光和基模振荡光在晶体内部的光斑的空间分布可通过热透镜加以控制。在端面抽运功率200 W附近时,实现了抽运光与基模振荡光较高程度匹配,光束质量因子M2由14.7改善为4.1。