Contrastive study on two kinds of semiconductor saturable absorber mirrors for side-pumped passively mode-locked Nd:YAG lasers

Abstract

Based on the reflectance of saturable absorber depended on the optical intensity and the interference theory, we investigate the reflectance bandwidth characteristic of the semiconductor saturable absorber mirror (SESAM). Two kinds of SESAMs, one of which satisfies the antiresonance condition, and the other does not, are contrastively studied in mode-locked Nd:YAG lasers. Results show that stabilized continuous-wave mode-locking can also be obtained in picosecond regime by the SESAM, which dose not fulfill the antiresonance condition, as good as the results obtained using a mature commercial SESAM satisfying the antiresonance condition. Because the bandwidth of picosecond regime mode-locked pulse is not broad; therefore a broad bandwidth and a minimal group velocity are not necessary. Without considering the limit of the antiresonance condition, the difficulty of designing and growing SESAMs will be decreased significantly and there will be more freedom in the macroscopic parameters.