Low propagation loss Ge-on-Si waveguides and their dependency on processing methods

Abstract

The successful fabrication of MIR Ge-on-Si waveguides written by both the high-resolution electron beam lithography (EBL) approach, as well as the wafer scale, high throughput approach using 365 nm i-line stepper lithography is reported. A low propagation loss of ∼2.7 dB/cm at a wavelength of 3.8 μm is shown for Ge-on-Si waveguides patterned using the i-line stepper. The waveguide etching technique, using reactive ion or deep-reactive ion etching, is also analyzed. Furthermore, the propagation loss values for both the lithographic techniques are found to be comparable. Therefore the advantage of using a simpler i-line stepper lithography for high volume fabrication is highlighted.