Characterization of Alumina Optical Waveguides Grown by Ion Beam Assisted Deposition for SPARROW Biosensors

Dielectric optical films with minimal surface roughness are required for biosensing applications since the coupling characteristics often used in signal transduction are dependent on the quality of the waveguides. This paper describes the fabrication and characterization of alumina-based optical waveguides for biomolecular detection devices. Alumina (Aluminum Oxide) Al 2 O 3 waveguides were chosen for their moisture stability and refractive index. Planar alumina optical waveguides were deposited on Borofloat substrates by a vacuum evaporation process using an ion beam assisted deposition technique. The deposited films showed RMS roughness of 0.3 nm - 0.5 nm and a range of refractive indices varying from 1.62 to 1.654 as a function of varying ion beam parameters such as oxygen flow rates and drive currents. The propagation losses for the TE 0 (Transverse Electric) mode of the alumina films at 632.8 nm wavelength were found to vary between 2 dB/cm ñ 6 dB/cm at a wavelength of 632.8 nm for TE 0 polarization as a function of ion beam parameters. It is shown that these factors influence the optical film quality and hold the potential for achieving further waveguide performance improvement for biosensing applications.