Frequency shifter for heterodyne interferometry measurements and device for heterodyne interferometry measurements having such a frequency shifter
The invention refers to a frequency shifter for heterodyne interferometry measurements, comprising a chip, an input waveguide configured to guide a light beam, at least four phase modulators, each being arranged to receive the light beam from the input waveguide and configured to modulate a phase of the light beam, an output combiner being arranged to let the light beams modulated by each phase modulator interfere, a first output waveguide coupled to the output combiner and configured to receive the modulated light beams constructively interfering at the output combiner, a second output waveguide coupled to the output combiner and configured to receive the modulated light beams destructively interfering at the output combiner, wherein the input waveguide, the phase modulators, the output combiner, the first output waveguide and the second output waveguide are arranged on the chip.
1. A frequency shifter for heterodyne interferometry measurements, comprising
a chip,
an input waveguide configured to guide a light beam,
at least four phase modulators, each being arranged to receive the light beam from the input waveguide and configured to modulate a phase of the received light beam and to output a respective modulated light beam,
an output combiner being configured to combine all of the modulated light beams,
a first output waveguide coupled to the output combiner and configured to receive a portion of each of the modulated light beams, and
a second output waveguide coupled to the output combiner and configured to receive a portion of each of the modulated light beams,
wherein the input waveguide, the phase modulators, the output combiner, the first output waveguide and the second output waveguide are arranged on the chip.
2. The frequency shifter of claim 1 , further comprising a first splitter having two output ports and arranged between the input waveguide and the phase modulators, wherein two of the phase modulators form part of a Mach-Zehnder interferometer which is respectively coupled to an output port of the first splitter.
3. The frequency shifter of claim 1 , wherein the first output waveguide is configured to emit the modulated light beams received from the output combiner to a surrounding of the chip.
4. The frequency shifter of claim 1 , further comprising a coherence detector having a first input port and a second input port, the coherence detector configured to detect differences in the amplitude and/or phase of light beams coupled in at the first input port and the second input port, wherein the coherence detector is arranged on the chip.
5. The frequency shifter of claim 4 , wherein the second output waveguide is coupled to the first input port of the coherence detector.
6. The frequency shifter of claim 4 , wherein the second input port is coupled to a receiver structure, wherein the receiver structure is at least partially arranged on the chip, and wherein the receiver structure is configured to receive light emitted by the first output waveguide and backscattered by the surroundings of the chip.
7. A device for heterodyne interferometry measurements, comprising
the frequency shifter of claim 1 ; and
a generator coupled to each of the phase modulators and configured to output a modulation signal to each of the phase modulators, the modulation signal defines the phase modulation, the modulation signal having a modulation frequency and a modulation phase,
wherein the generator is configured to generate the modulation signals such that at least two modulated light beams destructively interfere at the output combiner.
8. The device of claim 7 , wherein the generator is configured to generate one modification signal having a set modulation frequency and a set phase, one modification signal having the set modulation frequency and the set modulation phase plus 90°, one modification signal having the negative set modulation frequency and the set modulation phase, and one modification signal having the negative set modulation frequency and the set modulation phase minus 90°.
9. The device of claim 7 , further comprising a heat controller, a temperature sensor arranged at an output waveguide assembly coupling the phase modulators to the output combiner, and/or a heater arranged at the output waveguide assembly, wherein the temperature sensor is configured to measure at least a part of the output waveguide assembly and/or the heater is configured to heat at least a part of the output waveguide assembly, wherein the heat controller controls the heater based on the temperature detected by the temperature sensor such that an optical pathlength of the output waveguide assembly remains constant.
10. The device of claim 9 , further comprising an output waveguide assembly connecting the phase modulators to the output combiner, wherein the output waveguide assembly includes a Y-branch combiner and/or an 2×2 coupler, and wherein a first output of the 2×2 coupler is coupled to the output combiner and a second output of the 2×2 coupler is coupled to a control photodetector.
11. The device of claim 10 , wherein the first output waveguide and/or the second output waveguide include an output splitter, an output port of the output splitter is coupled to a control photodetector.
12. The device of claim 10 , wherein the generator generates the modulation signal based on a value output by the control photodetector and/or the heat controller controls the heater based on the value output by the temperature sensor.