<inline-formula><math display="inline" overflow="scroll"><mn>1</mn><mo>×</mo><mn>2</mn></math></inline-formula> optical waveguide filters based on multimode interference for 1.3- and 1.55-μm operation

Abstract

A novel multimode interference optical filter design in SiGe/Si for 1.3- and 1.55-?m operation is investigated. From the theory of large single-mode rib waveguides, the width of the rib waveguide and its height and etched depth were derived for a Ge content of x= 0.04. Using the modal propagation analysis method, the coupler length of the device is evaluated and the transmission characteristics are investigated. The results show that for 1.3 ?m, the optimum coupler length of the filter is 4710 ?m, with an extinction ratio of 17 dB; and for 1.55 ?m, the optimum coupler length of the filter is 5180 ?m, with an extinction ratio of 30 dB. For both filters, insertion loss is less than 0.1 dB.