Asymmetric Mach-Zehnder germano-silicate channel waveguide interferometers for quantum cryptography systems

Asymmetric Mach-Zehnder channel waveguide interferometers possessing a 1.1 ns delay in one of the arms were fabricated using flame hydrolysis deposition of silica glass on silicon. Two modules were combined to form a single time-division interferometer for optical pulses. The composite interferometer exhibited a high fringe contrast ratio of 1:200 making it eminently suitable for use in compact, low error-rate quantum cryptography systems.