<title>Diode-pumped femtosecond solid state lasers based on semiconductor saturable absorbers</title>

Abstract

`Real-world' applications of femtosecond pulses require laser sources that are reliable, compact, and easy-to-use. Diode-pumped lasers are one key step in this direction, and as a next key step we have developed and demonstrated a simple technique using semiconductor saturable absorbers to passively start and stabilize mode-locked lasers. Because the saturable absorber stabilizes soliton modelocking, we achieve self-starting modelocking over a wide cavity stability range, in contrast to KLM, which tends to require critical cavity alignment and is usually not self-starting. We discuss different saturable absorber designs. An A-FPSA is used in a diode-pumped Nd:glass laser (130 fs, 100 mW avg output power) and a Cr:LiSAF laser (45 fs, 80 mW output). A thin saturable absorber design provides self-starting mode- locking over a wavelength range of 30 nm, and a low-loss design supports a record mode- locked output power of 120 mW from a Cr:LiSAF laser. A dispersive saturable absorber mirror design combines both negative dispersion compensation and saturable absorption within one semiconductor device and produces a compact mode-locked Cr:LiSAF laser (160 fs, 25 mW) without the need of prisms for dispersion compensation. Finally, we present an optimized diode-pumped cavity layout for Cr:LiSAF which allows for higher output powers (> 1 W cw).