Chinese Optics Letters, Vol. 1, Issue 3, 03149 (2003)
Output beam analysis of high power COIL
Deli Yu1,2, Fengting Sang1, Yuqi Jin1, and Yizhu Sun1
- 1Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023
- 2Nanyang Technological University, EEE, Block S1, Nanyang Avenue, Singapore 639798
As the output power of a chemical oxygen iodine laser (COIL) increases, the output laser beam instability appears as the far-field beam spot drift and deformation for the large Fresnel number unstable resonator. In order to interpret this phenomenon, an output beam mode simulation code was developed with the fast Fourier transform method. The calculation results show that the presence of the nonuniform gain in COIL produces a skewed output intensity distribution, which causes the mirror tilt and bulge due to the thermal expansion. With the output power of COIL increases, the mirror surfaces, especially the back surface of the scraper mirror, absorb more and more heat, which causes the drift and deformation of far field beam spot seriously. The initial misalignment direction is an important factor for the far field beam spot drifting and deformation.