Tunable bandpass filters based on resonant optical tunneling

• Author / Creator

  Harrison, Timothy R.

• This thesis describes the design, fabrication and characterization of tunable bandpass filter devices based on optical tunneling. The filters were manufactured from the hybrid assembly of first hemi-cylindrical and later hemi-spherical lenses, with a multi-layer thin-film stack deposited on the flat surface of each lens. The two lenses were then clamped in intimate contact and piezo stack actuators were fixed in place to drive a small air gap between the two coated faces. Manipulation of the angle of incident light and the width of the µm-scale air gap between the two thin film stacks serves to tune the center wavelength and shape of the optical passband transmitted through the device. The theory of operation for these devices was developed previously, but that theory is expanded upon in this thesis.

  Depending on the desired operational range of the filter, different materials were used, with a NIR filter (range ~1000—1800 nm) fabricated using a-Si/SiO2 multilayer stacks, and a VIS filter (range ~400—700 nm) fabricated with Ta2O5/SiO2 films. Both filters were designed to produce flat-top passbands for TE-polarized light, with an approximately fixed fractional bandwidth. They also exhibit excellent orthogonal (TM) polarization and out-of-band rejection over the tuning range. For applications requiring a collimated tunable source, or in hyperspectral imaging, these filters could be an attractive alternative to current systems utilizing liquid crystal, acousto-optic, or grating based tunable filters.

• Subjects / Keywords

  • Optical tunneling
  • Hyperspectral imaging
  • Optics
  • Tunable bandpass filter

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-162x-kk24

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.