Ge/SiO₂ photonic crystal multichannel wavelength filters for short wave infrared wavelengths

Ge/SiO₂ multilayer type two-dimensional photonic crystals (PhCs) for short wave infrared (λ ∼ 2000 nm) application are demonstrated. The PhCs are fabricated by the autocloning method, which stacks multilayer on a glass substrate with initial line and space pattern by bias-sputtering. We verified their multi-channel wavelength filtering operation. Long wave pass or short wave pass filtering function is observed. Typical PhC dimensions are: Ge and SiO₂ thickness is 220 nm, total number of layers is 16, horizontal lattice constant is approximately 500 nm. Transmission losses are the order of 30%, which mainly originates from the absorption of Ge layer. Extinction coefficient (κ) of the sputtered Ge was estimated to be less than 0.05 for the wavelength range between 1600 and 2400 nm.