Department of Physics, Engineering Physics & Astronomy

Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy

Chemical and Mechanical Sensing with Optical Resonators: Microspheres and Guitar Pickups

Hans-Peter Loock
Queen's University

Date: Thursday, January 10, 2013
Time: 10:30 AM
Location: Stirling 501


In the last years we have exploited the sensitivity of optical resonators for measurements of optical absorption, refractive index, pressure, and strain. We focused, in particular, on measurements of the optical resonance frequency and of the optical loss of these resonators, since they are strongly dependent on the physical properties of the cavity, and can be measured without having to accurately determine a light intensity. I will focus on two different devices:

  • A silica microsphere is a high-Q cavity when its whispering gallery modes are excited. Phase-shift cavity ring-down spectroscopy can then be used to determine the optical loss induced by an adsorbing molecule. I will show that we can determine the absolute absorption cross section of a sub-monolayer of ethylene diamine through the N-H overtone band.
  • Photoacoustic spectroscopy can be conducted using fiber Bragg Gratings (FBGs) or fiber cavities as strain sensing elements. The same devices have also been used as 'pick-ups' for musical instruments. In a series of experiments we demonstrated that the Photonic Guitar pickup has a superior frequency response and far-superior signal-to-noise ratio over existing pick-up technology. A video file in which Paul Langlois (The Tragically Hip) demonstrates the guitar pickup will be shown.