Ge-laminated polarizer for 790-850-nm applications with extinction ratios larger than 50 dB and insertion losses below 0.4 dB

A laminated structure composed of alternating layers of Ge and SiO ₂ (Ge-LAMIPOL) is usable as a miniaturized polarizer at 790-850 nm in fiber optic gyroscopes, for instance. However, peeling of the sputter deposited layers, due to the weak binding strength between Ge and SiO₂, is a serious problem during the slicing process in preparation for assembly in the fiber. In order to improve the adhesive strength, the 1-nm-thick Si layers are inserted between Ge and SiO₂ layers. The Si layer functions as the adhesive layer via the Si-O bonding formation in place of the weaker Ge-O bond. The new Ge-LAMIPOL, including 125 layers of (1-nm Si)/(4.5-nm Ge)/(1-nm Si)/ (800-nm SiO₂) is successfully prepared without any fracture. The extinction ratio and the insertion loss were 51 and 0.33 dB at 850 nm, respectively, corresponding to 59.6 and 0.36 dB as the designed values