Optical device for detecting an acoustic wave
AssigneesCommissariat A L'energie Atomique Et Aux Energies Alternatives, Universite Grenoble Alpes, Cnrs, Institut Polytechnique De Grenoble
InventorsThomas Lauwers, Skandar Basrour, Jean-Guillaume Coutard, Alain Gliere, Guillaume Laffont
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Abstract
The invention relates to a device and method for detecting an acoustic wave propagating toward a membrane, the membrane carrying a waveguide comprising an optical cavity defining a resonant frequency. Under the effect of a vibration of the membrane, the resonance frequency of the optical cavity varies. The device includes a light source for directing a light wave into the optical cavity, and a servo circuit for servo-controlling the wavelength of the light wave to the resonant wavelength of the optical cavity. Monitoring the variation in the wavelength of the light wave allows an amplitude of the acoustic wave to be estimated.
Claims8
A device for detecting an acoustic wave, comprising:
- a membrane, carrying a waveguide, the membrane being configured to vibrate at a frequency of the acoustic wave;
- the waveguide comprising a first reflector, and a second reflector, each reflector reflecting light in a reflection spectral band, the waveguide being configured to vibrate with the membrane;
- the first reflector and the second reflector being spaced apart from each other, so as to form a resonant optical cavity, the resonant optical cavity defining a resonant wavelength, in the reflection spectral band;
- wherein the waveguide is configured to:
- transmit light at the resonant wavelength;
- and
- reflect light, in the reflection spectral band, not of the resonant wavelength;
- the device further comprising:
- a laser light source configured to emit a light wave at an emission wavelength, into the waveguide;
- a photodetector arranged to detect a light wave transmitted by the waveguide at the resonant wavelength;
- a servo circuit, connected to the light source and to the photodetector, and configured to servo-control the wavelength of the emission wave to the resonant wavelength of the resonant optical cavity at various times;
- and
- a processing unit connected to the servo circuit and configured to:
- determine a periodic time-dependent variation having a frequency corresponding to the frequency of the acoustic wave in the emission wavelength under the effect of a vibration of the membrane, the periodic time-dependent variation in the emission wavelength corresponding to a periodic variation in the resonant wavelength;
- and
- estimate an amplitude of the acoustic wave on the basis of the periodic time-dependent variation in the emission wavelength;
- wherein:
- the waveguide is formed directly on the membrane;
- the membrane exhibits, under the effect of the vibration, at least one vibration antinode, an amplitude of vibration being maximum at each vibration antinode;
- the waveguide lies level with at least one vibration antinode;
- and
- the first reflector and the second reflector are configured to deform under the effect of the vibration of the membrane.
Dependencies are inferred from the claim text.