Birefringent laser mirrors.

Narrow band mirrors composed of a polarizer, a stack of lossless birefringent crystals, and a conventional mirror are described. Curves showing the reflectance characteristics of the mirrors are included. Design data are tabulated for narrow band mirrors that have appreciable between-peak reflectances because of the Gibbs phenomenon as well as for slightly broader band mirrors with lower between-peak reflectances. Computations are presented in a series of graphs to demonstrate sensitivity of the response to the angular adjustment of the crystal elements. Electric tuning of the birefringent mirror is possible and can be enhanced by a double element design. The choice of electrooptic birefringent materials and the temperature sensitivity of the mirror's peak wavelength are discussed along with applications. An appendix provides computational aids for the synthesis of birefringent filters.