Study of saturable absorber materials for Q-switching dye laser

Abstract

Q-switching is a technology widely used in lasers to generate short pulses with high peak powers. In practice, Q-switching can be realized with various methods including mechanically by rotating mirror, actively either by acousto-optic or electrooptic method, or passively using a saturable absorber. The first two techniques have their own problems especially the spinning machine and the driver to get a shorter pulse duration. Therefore, passive Q-switch was chosen in this study because it requires less optical element inside the laser cavity and no outside driving circuitry and makes this technique simple and relatively cheaper compared to the other two techniques. Passive Q-switching is a better choice for those applications where compactness of the laser is a prime requirement. The objective of this project is to study and characterize the suitable material to be saturable absorber for passive Q-switching laser. The dye laser was utilized as a source of Q-switching laser. As a preliminary, the laser was calibrated to determine the best performance of laser beam. Various materials including 3, 3’- Diethyloxadicarbocyanine Iodide (DODCI), 1,3'-Diethyl-4, 2’-quinolyloxacarbocyanine Iodide (DQOCI) and 1,1'-Diethyl-4, 4’-carbocyanine Iodide (Cryptocyannine) and Chromium-doped Yttrium Aluminium Garnet (Cr4+: YAG) crystal are employed as a saturable absorber material. The pulse width, the single pulse energy and the peak power of the Q-switched laser output are measured. Two of the tested materials namely 1,3'- Diethyl-4, 2’-quinolyloxacarbocyanine Iodide (DQOCI) and Chromium-doped Yttrium Aluminium Garnet (Cr4+: YAG) crystal demonstrate a good performance to be a saturable absorber. The output characteristics of the passive Q-switch laser possess a uniphase of TEM00 mode.