Air-Suspended SU-8 Strip Waveguides With High Refractive Index Contrast

Integrated polymer photonics is efficient and cheap solution for many applications, such as optical communications and sensors. Waveguides are basic elements of photonic integrated circuits, and their performance directly influences optical circuit efficiency. However, it is a challenge to develop small footprint polymer waveguides with reasonable losses due to low refractive index comparing to cladding. In this letter, we present free-standing SU-8 waveguides with high refractive index contrast. SiO
₂
cladding is selectively etched, leaving only air as a cladding material; waveguides are supported by thin pillars. Removal of SiO
₂
cladding eliminates light leakage to substrate and provides better light confinement. Straight and bending SU-8 waveguides are numerically simulated and experimentally verified at λ = 1550 nm. We also report reduced propagation and bending losses in discussed waveguides.