Design, Fabrication, and Measurement of a Silicon Nitride Optomechanical Crystal

• Author / Creator

  Agnew, Thomas

• When a photon experiences a change in momentum of any form, be it being absorbed or reflected from a surface, the photon will exert a force upon that material. This force is called the radiation pressure force. One way that we can harness this radiation pressure force is to couple optical and mechanical systems together to form optomechanical systems. One such optomechanical system is the optomechanical crystal (OMC), which consists of an optical waveguide patterned periodically with holes. By placing a defect, in other words by modifying the shape of the holes, in the center of the pattern we can form an optical cavity between the two end regions of the waveguide. This optical mode within the OMC can then excite a mechanical breathing mode in the center of the waveguide through the radiation pressure force.

  Optical fiber networks typically use light with wavelengths in the range of 1260 to 1625 nm (184 to 238 THz) since these wavelengths minimize optical loss within the fiber. In order for the OMC to be resonant with light of this wavelength the OMC must be of similar size, limiting our geometry to the micrometer scale. Fortunately there exist many different techniques, such as electron beam lithography and reactive ion etching, which allow for fabrication of devices this small.

  In this work, we describe our methods for designing, fabricating, and measuring an OMC made from silicon nitride. Designing the OMC was done through simulation of the optical and mechanical modes using COMSOL Multiphysics. The OMCs were then fabricated at the NanoFAB Fabrication and Characterization Center at the University of Alberta. Light was coupled into the OMC using a dimpled-tapered fiber setup, then measurements of the optical and mechanical properties were done using either a direct detection scheme or a balanced homodyne phase detection scheme. The final device supported an optical mode at 1482.55 nm and a mechanical mode at 2.62 GHz with an optomechanical coupling rate of 98.66 kHz.

• Subjects / Keywords

  • Optomechanics
  • Silicon Nitride
  • Photonic Crystal
  • Optomechanical Crystal
  • Simulation
  • Fabrication
  • Homodyne

• Graduation date

  Spring 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-7v0f-jt74

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.