Cr:Colquiriite Lasers: Current status and challenges for further progress

Cr: Colquiriite laser materials (Cr:LiCAF, Cr:LiSAF, Cr:LiSGaF) own broad absorption bands in the visible region that allow direct-diode pumping by well-developed low-cost red diodes. Moreover, they possess broad emission bands in the near infrared that enable widely tunable laser operation (720–1110 nm), and generation of sub-10-fs light pulses via mode-locking. Furthermore, Cr: Colquiriite crystals can be grown with a very low loss level of 0.2%/cm, which enables the construction of high-Q-cavities, resulting in lasing thresholds below 1 mW, and slope efficiencies above 50%. High-Q-cavities constructed with Cr: Colquiriites could store large amount of intracavity laser powers which is off great interest: (i) for increasing the efficiency of intracavity nonlinear processes such as intracavity frequency-doubling, and (ii) for minimizing laser noise such as timing jitter noise in femtosecond operation. However, thermally and mechanically Cr: Colquiriites have glass like properties. Hence, average power scaling has been challenging in the cw and femtosecond Cr: Colquiriite lasers, as well as in their amplifiers. In this paper, we will review research efforts over the last decades, in developing robust, low-cost, highly-efficient, and tunable cw and femtosecond laser sources based on diode-pumped Cr:Colquiriite gain media. Challenges for future progress will also be discussed.