Quantum cascade laser tuning by digital micromirror array-controlled external cavity

Abstract

A quantum cascade laser (QCL) tuning mechanism based on an external laser cavity containing a Micro ElectroMechanical System (MEMS) spatial light modulator in the form of a two-dimensional digital micromirror array (DMA) is described. The laser is tuned by modulating the reflectivity of DMA micromirror pixels under computer control. The resulting functionality enables fast (<0.1ms switching time) digitally controlled random-access wavelength tuning, high-bandwidth wavelength modulation (~30kHz modulation rate), and stable wavelength locking of the laser output. With one or more QCL gain elements built into the cavity, it is possible to cover a wide portion of the mid-wave and/or long-wave spectral range with a single device. The fast wideband digitally controlled laser tuning technology described is applicable to other tunable laser including solid-state, diode, gas, and fiber lasers.