Experimental Study of Optical Nonlinearities in a Broadband Semiconductor Saturable Absorber Mirror

The negative nonlinear index of a semiconductor saturable absorber mirror (SESAM) was investigated by using the reflection Z-scan technique. This is an experimental demonstration, for the first time to our knowledge, that the SESAM possesses comparable negative nonlinear index n₂= -2.35×10^-10,esu, which may have important implications in design and alignment of Kerr-lens mode-locking based on the self-focusing effect.