Hermetically sealed optical subassembly

Abstract

An optical subassembly includes a high speed ceramic substrate having cavity containing an array of photodetectors, and a glass or silicon window for covering the cavity and forming a hermetic seal. A retainer is attached to the window for direct or indirect attachment to a fiber. The hermetic seal protects the device from moisture and other environmental conditions. The window has an index of refraction higher than air that effectively increases the optical pathlength sufficient while maintaining an acceptable coupling efficiency between the optoelectronic device and a fiber. This provides increased spacing within which to place and interconnect components within the cavity on the substrate. In alternate embodiments, the window is decoupled from direct contact with the retainer via a metal frame or ring. Decoupling the window from direct contact with the retainer helps prevent cracking of the window due to mismatches in the coefficients of thermal expansion between the window and the retainer.