Abstract
Low-loss waveguides integrated on a silicon substrate are essential components in the design and
fabrication of photonic circuits. For this application, a wide operational bandwidth - from visible to
infrared wavelengths - is critical. Previous research has yielded waveguides made with various materials
and geometries. Several of these devices have achieved low, <0.1dB/cm loss in either the visible or the
near-IR. However, to obtain effective confinement of light from the visible through the near-IR, it is
necessary to develop waveguides which have near-constant loss and minimal non-linear effects across the
entire wavelength range.
To overcome this challenge, we have developed novel silica on silicon waveguides fabricated
using conventional lithographic techniques and CO2 laser reflow. The entire waveguide is elevated above
the higher refractive index silicon substrate, creating an isolated, air-clad waveguide. The cylindrical
waveguide's loss was determined by coupling light from 658nm, 980nm, and 1550nm lasers into the
waveguide using lensed optical fibers. Due to the inherently low material loss of silica and the isolation
from the silicon substrate, the device has low optical loss (0.7-0.9dB/cm) and linear behavior across the
entire wavelength, polarization, and input power ranges studied. These on-chip waveguides will benefit
many applications, including biodetection and integrated photonics.
