Research on Thermal Effect and Mode Properties of a Q-Switched Laser by Using Shack-Hartmann Wavefront Sensor

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.308-310.1444 ◽

2011 ◽

Vol 308-310 ◽

pp. 1444-1447

Author(s):

Xiang Zhang

Keyword(s):

Thermal Lens ◽

Matrix Theory ◽

Second Harmonic ◽

Spherical Aberration ◽

Beam Quality ◽

Wavefront Sensor ◽

Wavefront Aberration ◽

Output Beam ◽

Lens Effect ◽

Thermal Lens Effect

Results of an experimental and theoretical analysis of the proprerties of a LD pumped laser using a stable resonator and second harmonic conversion crystal are presented. The influence of thermal lens effect on laser output mode and beam quality has been discussed briefly by using the transfer matrix theory. In this paper, further experiment on the output beam quality of a LD pumped acousto-optic Q-switched laser has been also performed by adopting Shack-Hartmann wavefront sensor and Zernike mode reconstruction theory. Using this method, PV and RMS error of aberration wavefront, the first 35-order Zernike aberrations can be acquired. Furthermore, Strehl ratio curve of output beam and the distribution of circle energy can also be obtained by further calculation, so mode properities can be comprehensively understood. Experimental results show that the beam wavefront aberration is mainly concentrated in the first 15 orders of Zernike aberration, mainly including the defocus A3, the low-order astigmatism A4 and A5, the coma and spherical aberration because of the thermal-lens effect.

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Research on Thermal-Effect and Phase Properties of a Q-Switched Laser Using KTP Frequency-Doubling Crystal

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.282-283.505 ◽

2011 ◽

Vol 282-283 ◽

pp. 505-508

Author(s):

Xiang Zhang

Keyword(s):

Thermal Effect ◽

Matrix Theory ◽

Beam Quality ◽

Frequency Doubling ◽

Wavefront Aberration ◽

Output Beam ◽

Ratio Curve ◽

Thermal Lens Effect ◽

Coma Aberration

Results of an experimental and theoretical analysis of the proprerties of a LD pumped laser using a plano-concave stable resonator and KTP frequency-doubling crystal material are presented. The influence of thermal lens effect on laser output mode and beam quality has been discussed briefly by using the transfer matrix theory. In this paper, further experiment on the output beam quality of a LD pumped acousto-optic Q-switched laser has been also performed by adopting Hartmann-Shack wavefront sensor and Zernike mode reconstruction theory. Using this method, the PV and RMS values of the aberration wavefront, the frontal 35-order Zernike aberrations can be acquired, and the Strehl ratio curve of the output beam and the distribution of circle energy can also be obtained by calculation, so the mode properities can be fully understood. The experimental results show that the beam wavefront aberration is mainly concentrated in the frontal 15 orders of Zernike aberration, mainly including the defocus A3, the low-order astigmatism A4 and A5, and the coma aberration A6 and A7 because of crystal thermal effect.

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Experiment Study of Influence on Laser Beam Quality Induced by Thermal Lens Effect and Depolarization Effect

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.43.670 ◽

2010 ◽

Vol 43 ◽

pp. 670-674

Author(s):

Xia Ye ◽

Hong Bing Yao ◽

Yan Qun Tong ◽

Yong Kang Zhang ◽

Ruo Xi Cao ◽

...

Keyword(s):

Laser Beam ◽

Thermal Lens ◽

Thermal Effects ◽

Beam Quality ◽

Double Refraction ◽

Lens Effect ◽

Laser Beam Quality ◽

Depolarization Effect ◽

Output Laser ◽

Thermal Lens Effect

For high power and repetitive Nd:Glass laser, there would appear serious thermal effect due to the significantly-enhanced pumping optical power density in laser rod, which would induce thermal double refraction, phase distortion, thermal focusing, thermal depolarization, etc. Thus, the laser output power and beam quality would be influenced severely. Influence of thermal lens effect and depolarization effect caused by thermal stress double refraction on laser beam were studied in this paper for high power and repetitive laser. In the experiment of thermal lens effect, change of the laser spot by thermal lens effect was recorded after a TEM00 He-Ne laser beam passing through the Nd:Glass rod pumped by Xe lamp, and the corresponding optical compensator was applied to eliminate the thermal lens effect to improve the beam quality. Configuration of polarizer was designed in our experiment to research the depolarization effect caused by thermal stress double refraction. First, emergent light distribution and loss factor caused by double refraction was calculated according to the theoretical model. Then the exiting cone-shaped polarized light intensity distribution was obtained through the experiment. It could be obtained from the experiments that thermal lens effect and depolarization effect caused by thermal double refraction would reduce the output laser beam quality to varied extents. As the number of laser pulses increased, thermal effects began to emerge and the output laser energy apparently decreased; when the thermal effects steadied, the output energy would be tending towards stability.

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