Abstract
Optical characteristics of the laser gain medium, saturable absorber and reflectivity of the output coupler mirror determine the output performance of a passively Q-switched microchip laser. However, the conventional method of enhancing the peak power, in which the pulse width is narrowed by shortening the cavity length, has a complex chip fabrication process. Therefore, this thesis presents a novel means of increasing the peak power of a diode pumped passively Q-switched microchip laser with a fixed cavity configuration. The thermal focusing theory indicates that the laser mode size is enhanced by increasing the pump size and, simultaneously, increasing the peak power. Experimental results indicate that the proposed method enhances the pulse energy by 50% while simultaneously increasing the pump size by 50%, thereby increasing the output peak power under a fixed cavity configuration proportionally. Results in this study demonstrate that the proposed method optimizes the output peak power of a diode pumped passively Q-switched microchip laser without relying on a complex chip fabrication process. Furthermore, a compactly tunable visible laser is demonstrated by combing a monolithic PPLN and the passively Q-switched microchip laser, demonstrated herein.