Optical modulation apparatus and measurement method
OwnerWalter Lukoszinventor
Life of this patent
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Abstract
In an optical micromechanical method for changing the phase of guided waves and a measurement method for measuring very small mechanical displacements and/or mechanical forces or pressures, including the pressure of sound waves and ultrasonic waves, and/or accelerations, the distance d between a section (1') of an optical waveguide (1) in an integrated optic or fibre optic circuit and a phase-shifting element (5) separated from said section (1') by a gap (4) is varied by forces (6) or by thermal expansion due to changes in temperature. The phase of the guided wave (3) is thereby modulated, and reciprocally the changes in distance d and hence small mechanical displacements and the forces (6) which produce them are determined from the measured phase changes.
Claims29
A method for changing the phase of guided waves and measuring very small mechanical displacements comprising the steps of
- providing a waveguide (1) having a first waveguide section (1') with an effective refractive index N and a phase shifting element (5) spaced from the waveguide section (1') by a gap (4) having a width d,
- filling the gap (4) with a medium having small absorption and a refractive index n<N, and either
- (a) varying the width d of the gap as a function of time while passing an optical wave (3) through the waveguide, the width d of the gap being sufficiently small so that the refractive index of the waveguide and the phase of the wave ar changed by interation of the evanescent field of the wave with phase-shifting element 3 or surface layers (13) of phase shifting element (5) facing the waveguide section (1'), while absorbing or coupling out of the waveguide section (1') substantially no power of the guided wave (3) by the phase shifting element (5), or
- (b) measuring changes of the effective refractive index N and the phase of the optical wave (3) as a measure of changes of the width d.
An apparatus comprises an optical waveguide (1) or an integrated optic or fiber optic circuit, which contains at least one optical waveguide, and a phase-shifting element (5) located at a small variable width d opposite section (1') of the waveguide (1) and separated by a gap (4) from said section.
Dependencies are inferred from the claim text.