Submicrometer-Thick Low-Loss As $_2$S$_3$ Planar Waveguides for Nonlinear Optical Devices

We describe a fabrication process for and the characterization of submicrometer-thick As
₂
S
₃
waveguides. Poly(methylmethacrylate) and bottom antireflective coating were employed as thin protective layers prior to photoresist patterning in order to prevent the attack of the As
₂
S
₃
film by an alkaline developer. Propagation losses of ~0.2 and 0.6 dB/cm were measured for 4- and 2-¿m-wide waveguides fabricated from 0.85-¿m-thick films. Slightly higher loss in the transverse-magnetic mode may be the result of surface scattering of the rougher etched sidewalls.