Design and Operation of a Continuous-Wave, Single-Mode Nd:YVO4 Ring Laser

• Main Authors: Chi-Yang Wu, 吳季陽
• Other Authors: Chen-Yau Tang
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/78721089822525470431

碩士 === 淡江大學 === 物理學系 === 87 === The design and operation of a continuous-wave, single-mode Nd:YVO4 ring laser has been studied both experimentally and theoretically. The main purpose is to investigate the effects of optical feedback on the two oppositely directed optical fields in the ring laser and generate quasi-unidirectional, single-mode operation. In experiment, a GaAlAs diode laser with a maximum output power of 0.6 W at 808nm was employed as the pumping source, and a right-angle triangular resonant cavity was constructed with available optical components. Bi-directional operation of the ring laser generates four output beams: two weak and two stronger ones. One of the two weak output beams was used for optical feedback, the other for observing laser spectral characteristics. The two stronger output beams were used for direct comparison of the intensity of the two intracavity fields. With no optical feedback, the counter-propagating fields in the cavity had the same oscillation threshold, and their powers increased with the pumping power. Although they competed strongly for gain and their output powers were unstable, their total power was almost a constant. With optical feedback, the oscillation threshold was slightly lowered; the intensity ratio of the two output beams increased with the pumping power, and the maximum ratio could go over 100. Although quasi-unidirectional, single-mode laser output may be generated by this way, but it is difficult to maintain long-term stability. Theoretically, we analyzed the effects of optical feedback on the threshold and output powers of the ring laser. We found that the thresholds of the counter-propagating beams should be different, and the intensity ratio of the output beams is not a fixed constant, which is related to the pumping power. These preliminary results describe qualitatively the characteristics of the ring laser. In addition, we also discussed how to further improve the ring laser.