Contents I. Introduction
Kerr-Lens locked (KLM) Cr3+ : LiSrAlF6 (Cr : LiSAF) lasers are attractive femtosecond-pulse sources because the laser material can be directly pumped by diode lasers and has a broad emission band (FWHM 200 nm) almost comparable with that of Ti : sapphire. Diode-pumped KLM Cr : LiSAF lasers could be compact and inexpensive sub-10-fs pulse sources. Since Cr : LiSAF was first reported in 1989 [1], mode-locked Cr : LiSAF lasers have been demonstrated [2]–[11]. Femtosecond pulses from a Cr : LiSAF laser were also launched into a photonic crystal fiber to generate white-light frequency comb [12] for applications in optical frequency metrology. The typical pulse durations for Cr : LiSAF lasers without chirped mirrors were limited to no less than 18 fs [7] before our recent reports [10], [11].
