Wavelength selection for the far-infrared p-Ge laser using etched silicon lamellar gratings

A lamellar mirror made from Si wafer by anisotropic chemical etching and coated with gold has been demonstrated as an intracavity wavelength selector for the far-infrared p-Ge laser. The etching process produces rectangular grooves with precisely predetermined depth and 100nm surface smoothness. This lamellar-grating structure defines the resonant laser wavelength within the broad tuning range of the p-Ge laser. Single wavelength laser operation with this mirror has been demonstrated on the third-order resonance with an active cavity finesse of at least 0.09.