Abstract

Silicon-on-insulator (SOI) structures offer the unique ability to integrate long wavelength photonic devices into the CMOS integrated circuit (IC) process. The large index step between SiO₂ and Si (Δn~2.0) permits the use of thin layers ( < 1.0 µm cladding ) in SiO₂/Si/SiO₂ waveguide structures, making them compatible with VLSI technology. This large index step does not prevent single-mode wave propagation and single mode waveguides with low loss have been demonstrated at λ = 1.55 µm [1]. Further, the use of Si-Ge heterostructures permits the realisation of Si-based optoelectronic detectors in the 1.2 to 1.6 µm wavelength range [2]. Therefore, development of optical and optoelectronic devices in SOI offers a path towards low-cost, monolithic optoelectronic circuits. We report here the fabrication of a number of guided wave optical circuits in SOI technology including 3 dB directional couplers with excess insertion loss of~1.9dB at λ = 1.55 µm, an asymmetric Mach-Zehnder wavelength filter, and a 5 × 9 integrated optical star coupler with excess insertion loss of 1.3 dB and good uniformity. These optical circuits are used in cascaded Mach-Zehnder wavelength filters and phased-array waveguide grating filters for wavelength-division-multiplexed (WDM) networks.

© 1996 Optical Society of America