Design of an Integrated Dual-Mode Interferometeron 250 nm Silicon-on-Insulator

The design of a highly efficient integrated dual-mode interferometer with single-mode inputs and outputs and simple fabrication steps in a silicon-on-insulator platform with CMOS compatible technology is presented. Consisting of only one waveguide and two special mode converters, the device offers high sensitivity and immunity to input power fluctuations and temperature changes. Special attention is paid to the design of low-loss mode converters with two single-mode outputs for total power tracking. Considerations on temperature influence, fabrication tolerances, and dual mode waveguide sensitivity conclude the theoretical part. Experimental results of a single-port dual-mode interferometer show extinction ratios up to 31 dB and insertion losses of less than 1 dB at a wavelength of 1550 nm. With an additional functional polymer layer, the selective detection of various concentrations of L-Boc-phenylalanine anilid in an ethanol-water solution is demonstrated.