Research on Mechanism of Mode Locking Using Semiconductor Saturable Absorption Mirror in a Solid Laser of Pico-second

In this paper,the mechanism of mode-locking using a semiconductor saturable absorption mirror(SESAM) in solid laser was analyzed.We proposed a new opinion on how SESAM works to realize mode locking.It is not just an absorber but also a gain medium when working in all-solid laser because of the special structure of SESAM.If the gain and loss keep balance in cavity,continuous wave mode-locking(CWML) can be realized.