Patent ID: 8089684

Claim:
A phase shifter device for shifting a phase of an oscillation signal, comprising: a laser that produces a laser output beam at a laser carrier frequency; an optical interferometer located in an optical path of the laser output beam to receive the laser output beam and comprising an optical splitter that splits the laser output beam into a first laser beam and a second laser beam, a first optical path that receives the first laser beam, a second optical path that receives the second laser beam, and an optical combiner where the first and second optical paths meet and terminate, the optical combiner combing the first laser beam and the second laser beam to produce a combined optical output; an optical modulator coupled in the second optical path of the optical interferometer to cause a modulation of light in the second optical path at a modulation frequency in response to an input oscillation signal oscillating at the modulation frequency to introduce modulation sidebands at two sides of the laser carrier frequency in the second optical beam; an optical resonator optically coupled in the second optical path between the optical modulator and the optical combiner to filter the second optical beam output by the optical modulator to transmit light at a selected modulation sideband while rejecting light outside the selected modulation sideband, including light at the laser carrier frequency and one or more other modulation sidebands; a photodetector located to receive the combined optical output from the optical combiner of the optical interferometer and to convert the received combined optical output into an output oscillation signal whose phase is shifted relative to a phase of the input oscillation signal by a relative optical phase shift between the first optical path and the second optical path of the optical interferometer.