극초단 펄스 Cr4+:YAG 레이저의 제작 및 동작 특성

Abstract

We have developed a mode-locked ultra-short pulse Cr4+:YAG laser, as well as a continuous wave Cr4+:YAG laser. The laser was pumped by a Nd:YAG laser and its characteristics were investigated. In continuous wave mode, we obtained as much as 600 ㎽ at 1.436 ㎛ with pumping power of 6 W, by using an output coupler with a reflectivity of 98%. The power slope efficiency was 10%, when the gain medium was cooled to 19℃. The tuning range was varied from 1.39 ㎛ to 1.55 ㎛ and the maximum power was 400 ㎽ at 1.492 ㎛ with a 3-plate birefringent filter. The Cr4+:YAG laser was mode-locked by a Kerr lens mode locking method. Mode locking at 1.436 ㎛ was initiated by slightly rocking a mirror mount. But the pulses were very unstable because of the strong water absorption at this region. So we shifted the lasing wavelength to 1.492 ㎛ by using a 3-plate birefringent filter. Then we obtained stable state mode-locking with the maximum average power of 280 ㎽ for a pumping power of 6 W. The pulse width of 43 fs was measured using an autocorrelator and the repetition rate was 104.5 ㎒.