Multilayer mirrors capable of >99.9% reflectivity in the far infrared (70−200 µm wavelengths) were constructed using thin silicon etalons separated by empty gaps. Calculations indicate that only three periods are required to produce 99.9% reflectivity because of the large difference between the index of refraction of silicon (3.384) and the vacuum (1). The mirror was assembled from high-purity silicon wafers, with resistivity over 4000 Omega cm to reduce free-carrier absorption. Wafers were double-side polished with faces parallel within 10 arc sec. The multilayer mirror was demonstrated as a cavity mirror for the far-infrared p-Ge laser. Dependence of reflectivity on design accuracy was considered.
© 2005 Optical Society of America
(140.3070) Lasers and laser optics : Infrared and far-infrared lasers
(140.5960) Lasers and laser optics : Semiconductor lasers
(230.1480) Optical devices : Bragg reflectors
(230.4170) Optical devices : Multilayers
(260.3090) Physical optics : Infrared, far
Todd W. Du Bosq, Andrey V. Muravjov, Robert E. Peale, and Christopher J. Fredricksen, "Multilayer silicon cavity mirrors for the far-infrared p-Ge laser," Appl. Opt. 44, 7191-7195 (2005)