Fabrication and optimization of uniform output couplers for far-infrared lasers

An improved technique for the fabrication of uniform output couplers for far-infrared lasers has been developed. The technique includes a process for uniformly removing material from the back side of the coupler's substrate to tune the coupler's reflectivity precisely to the specified value for a particular laser line. Depending on the condition of the coupler after use, it can be retuned to another laser line, which lies within the coupler's reflectance envelope. Furthermore, when there is the possibility of lasing at two different laser wavelengths (as happens with some far-infrared lasers), it is possible to optimize the coupler for one wavelength while at the same time detuning the other wavelength. The fabrication and optimization of these devices are discussed.