Saturable Absorbers for Solid-State Lasers

Abstract

This chapter gives a comprehensive introduction to saturable absorbers, introducing macroscopic parameters such as modulation depth, nonsaturable loss, saturation fluence, and inverse saturable absorption independently of any specific saturable absorber materials. We distinguish between slow and fast saturable absorbers with different rate equation models and derive the nonlinear reflectivity model functions when the saturable absorber material is integrated with a highly reflective mirror, again independently of the specific material properties but simply reduced to the macroscopic parameters. There is then a more detailed introduction to semiconductor saturable absorber mirrors (SESAMs), the underlying physics of semiconductor saturable absorbers, and specific SESAM designs, optimized for antiresonance versus resonance, dispersion, ultrabroadband, and standing wave field enhancement. SESAM damage and characterization to determine the relevant macroscopic parameters is derived in detail and an outlook is given with regard to other saturable absorber materials.