Jong Rak Park

Characteristics of a birefringence compensation scheme in nd3+ : Yag rods using a polarization rotator and imaging optics

A numerical model based on ray optics formulation taking the optical path length into account was described and applied to numerical investigations on a thermal birefringence compensation scheme proposed and experimentally demonstrated by Q, Lüet al. [Opt. Quantum Electron.28 (1996) 57]. Taking into consideration the thermal lensing effects of laser rods depolarization losses and spatial intensity profiles of depolarized beams were calculated for the scheme. It was theoretically confirmed that using a polarization rotator and imaging optics effective compensation for the birefringence in rods is possible for a wide range of pumping power.

Stable range enhancement in a symmetric confocal two-rod resonator with 90/spl deg/ optical rotator

We propose a method to eliminate the narrow unstable region of a symmetric two-rod resonator with a 90/spl deg/ optical rotator which is used to compensate for thermal birefringence of the laser rod. The narrow unstable region is caused by the difference between the thermal focal lengths of the radial and tangential directions of a laser rod. Using the g-diagram analysis, we find that the narrow unstable region can be removed in the resonator configuration of a symmetric confocal type. We investigate the effect of the distance between two rods of the proposed resonator on the stability and the beam quality.

Compensation of polarization distortion of a laser beam in a four-pass Nd:glass amplifier by using a Faraday rotator

Effects of thermally induced birefringence in the laser rod on the performance of a degenerate four-pass Nd:glass amplifier are investigated by numerical models in this study. The spatial intensity profile of a depolarized beam, the amount of depolarization, and the temporal profile of an amplified output pulse are obtained for several schemes of the amplifier. It is found that the efficient compensation of the polarization distortion by introducing a Faraday rotator at the proper position in the amplifier can lead to stable high-contrast single pulse amplification.

Surface Roughness Measurement by Using Interferometer and Active Interferometer Stabilization

The profile of the mirror surface is measured by using optical phase shift method and Twymann-Green interferometer. Phase map is calculated by applying 4–buckets method and Vikhagen phase shift algorithm is applied to escape convolution errors. From that the obtained roughness of the mirror surface is around 20 nm rms roughness value. Also, the interferometer was stabilized by using fringe locking method. Also, we propose two colors method very precise surface profile and the length can be measured in the harsh environmental conditions.

Surface profile measurement by using stabilized polarization interferometer module

In this paper, we used the polarization interferometer for the surface measurements with stabilized interferometer module the polarizing beamsplitters, waveplates, etc. So we get four shifted interference patterns (0/spl deg/, 90/spl deg/, 180/spl deg/, 270/spl deg/). The stabilized He-Ne laser was used for the this measurement. The profile measurements from the interference pattern by using Twyman-Green interferometer has been done by using mathcad and FFT method.