The Study of the Passively Q-Switched Nd:YAG/Cr4+:YAG Laser with External Modulation

• Main Authors: Chien Hung Wang, 王健鴻
• Other Authors: Sheng Lung Huang
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/30600988871297783396

碩士 === 國立中山大學 === 光電工程研究所 === 87 === The timing jitter is a very serious problem in a passively Q-switched laser. However, most of the work of passively Q-switched laser concentrated on the shortening the pulsewidth, increasing the pulse energy or peak power. Little work has been done on the timing jitter for a passively Q-switched laser. In this study, a theoretical simulation is provided to explain the timing jitter and a new method is proposed to improve this problem. Our simulation result indicated that the spontaneous noise in the microwatt range significantly affects the repetition rate of passively Q-switched laser and creates large timing jitter. The phase of modulation signal is also found to be a crucial factor for reducing the timing jitter and can be improved up to 92%. A Nd3+:YVO4 microchip laser with wavelength of 1064 nm is employed as a modulation source to modulate the population of both ground and excited state of Cr4+:YAG simultaneously. A polarized beam-splitter(PBS) is used to direct the modulation beam onto the Cr4+:YAG crystal. A focus lens in front of the microchip laser is used for shaping the laser beam to match with the cavity mode. A function generator is used to provide the microchip laser a modulated pumping source. The timing jitter modulated with the microchip laser is then monitored by a 500 MHz digital scope. The experimental result has shown that the external modulation by a microchip laser proposed by us indeed improve the timing jitter up to 50%.