Design and characterization of semiconductor-doped silica film saturable absorbers

Nonepitaxially grown, rf sputtered semiconductor-doped silica film saturable absorbers have recently been developed as a versatile, easy to fabricate, cost-effective alternative to epitaxially grown semiconductor saturable absorbers. Characterization of their linear and nonlinear optical properties reveals trends that permit the development of guidelines for optimizing these devices for a particular laser system. Operation near the onset of absorption, the use of films with large nanocrystallites, and high rapid thermal annealing temperatures result in saturation fluences as low as 640 μJ/cm² at 1.54 μm. These materials can be used to start Kerr-lens mode locking in a wide range of solid-state lasers.