In a Single Mode Laser, a grating is etched into the active region to force the operation of the laser at very specific wavelength determined by the grating periodicity. As a result, the laser emits on a single spectral setting which may be adjusted slightly by changing the temperature of the active region.

Cryogenic Lasers are these lasers which operate only at temperatures < -30°C, typically at liquid nitrogen temperatures. While modern lasers usually operate at room temperature, some specific wavelength ranges are only attainable at these cryogenic temperatures. Both Pulsed and CW chips are available.