Broadband Mid-Infrared Solid-State Lasers

A survey of broadband Co²⁺- and Cr²⁺-based lasers is presented. These mid-IR sources, operating in the very interesting “molecular fingerprint” region between ~1.6 and 3.5 μm offer the broadest bandwidth from all solid-state vibronic lasers. The emphasize is made on Cr²⁺-doped lasers, which have not only the widest and the highest gain, but also operate at room-temperature and produce the shortest pulses of only several optical cycles around 2.5 μm directly from the resonator. Ten years after their invention, Cr²⁺-doped lasers have come of age and emerge in applications, demanding high power and extreme bandwidth. The paper reviews advances in the existing and novel Cr²⁺-based lasers, such as mixed Cr²⁺:ZnS_xSe_1−x, Cr²⁺:CdMnTe and Cr²⁺:CdZnTe lasers, which are likely to extend these features even further, and briefly describes a number of novel and yet upcoming applications. The first steps towards electrically pumped nanocrystalline lasers are described and the underlying physics is outlined.

Keywords: Transition metal doped II-VI; Cr²⁺:ZnSe; Cr²⁺:ZnS; Cr²⁺:CdSe; tunable mid-infrared lasers; ultrashort-pulsed mid-infrared lasers; mid-infrared random lasers.