Laser phase noise control system and method

Abstract

A multi-frequency laser system includes a first beam splitter configured to split a first beam into a high-power portion and a low-power portion of the first beam, and a second beam splitter configured to split a second beam into a high-power portion and a low-power portion of the second beam, wherein the frequency of the first beam is shifted relative to the frequency of the second beam. The system includes a combiner configured to combine the low-power portion of the first beam and the low-power portion of the second beam to generate a heterodyne beam used to reduce the phase error between the high-power portion of the first beam and the high-power portion of the second beam.

Claims

1. A first beam splitter configured to split a first beam into a high-power portion and a low-power portion of the first beam, A second beam splitter configured to split a second beam into a high-power portion and a low-power portion of the second beam, The system includes an electro-optic modulator configured to generate sidebands of the low-power portion of the first beam at an offset frequency from the frequency of the low-power portion of the second beam, The frequency of the first beam is shifted relative to the frequency of the second beam, A laser system in which the phase noise between the sideband of the low-power portion of the first beam and the low-power portion of the second beam is used to reduce the phase error between the high-power portion of the first beam and the high-power portion of the second beam.

2. The laser system according to claim 1, wherein the offset frequency between the sideband of the low-power portion of the first beam and the low-power portion of the second beam is less than the frequency difference between the first beam and the second beam.

3. The system includes an oscillator configured to generate an oscillation signal having an oscillation frequency equal to the frequency difference between the frequency of the low-power portion of the first beam and the sideband of the low-power portion of the first beam, The laser system according to claim 2, wherein the electro-optic modulator is configured to use the oscillation signal to generate sidebands of the low-power portion of the first beam.

4. The oscillator, A first signal generator configured to generate a first signal generator output, wherein the frequency of the first signal generator output is equal to the offset frequency, A high-frequency oscillator configured to generate a high-frequency signal output having a high frequency corresponding to half the shift of the frequency of the first beam relative to the frequency of the second beam, The laser system according to claim 3, comprising: a first mixer configured to mix the output of the first signal generator with the high-frequency signal output in order to generate the oscillation signal.

5. To generate a heterodyne beam, the system includes a combiner configured to combine the sidebands of the low-power portion of the first beam and the low-power portion of the second beam, The laser system according to claim 4, wherein the heterodyne frequency of the heterodyne beam represents the phase noise between the sideband of the low-power portion of the first beam and the low-power portion of the second beam.

6. The photodetector includes a photodetector configured to detect the heterodyne beam and generate a detected heterodyne signal using the detection of the heterodyne beam, The detected heterodyne signal is The phase noise between the sideband of the low-power portion of the first beam and the low-power portion of the second beam, The laser system according to claim 5, comprising detection phase noise generated by the photodetector when detecting the heterodyne beam.

7. To generate a noise-free detection heterodyne signal with respect to the output of the photodetector, the system includes a phase-locked loop configured to suppress detection phase noise in the detection heterodyne signal, The laser system according to claim 6, wherein the noise-free detection heterodyne signal includes phase noise between the sideband of the low-power portion of the first beam and the low-power portion of the second beam.

8. A second signal generator configured to generate a second signal generator output having a frequency equal to the offset frequency, The laser system according to claim 6, further comprising a second mixer configured to mix the detected heterodyne signal with the output of the second signal generator in order to generate an error signal indicating the detected phase noise.

9. Includes a servo loop filter configured to receive the error signal and generate a control signal using the error signal, The laser system according to claim 8, wherein the control signal frequency modulates the first signal generator such that the modulated output of the first signal generator includes the detection phase noise.

10. The laser system according to claim 9, wherein the first mixer is configured to mix the modulated first signal generator output with the high-frequency signal output such that detection phase noise of the detection heterodyne signal is suppressed and a noise-free detection heterodyne signal is generated with respect to the output of the photodetector, the noise-free detection heterodyne signal includes phase noise between the sidebands of the low-power portion of the first beam and the low-power portion of the second beam.

11. A third signal generator configured to generate a third signal generator output having a drive frequency value in addition to a frequency approximately equal to the offset frequency, A third mixer is configured to mix the output of the third signal generator with the modulated output of the first signal generator in order to generate a third mixer output signal, An acoustic-optic modulator configured to correct the phase error between the high-power portion of the first beam and the high-power portion of the second beam by modulating the high-power portion of the first beam using the third mixer output signal, The laser system according to claim 9, further comprising a radio frequency switch electronically coupled to the third mixer and the acousto-optic modulator, the radio frequency switch configured to switch the modulation by the acousto-optic modulator using the output signal of the third mixer on or off.

12. The laser system according to claim 1, wherein the high-power portion of the first beam and the high-power portion of the second beam perform at least one of (a) entangling qubits in a quantum computer and (b) providing a first laser light source and a second laser light source to a coherent heterodyne optical system.

13. The laser system according to claim 1, wherein the high-power portion of the first beam and the high-power portion of the second beam provide a first and second laser light source to a coherent heterodyne optical system, and the coherent heterodyne optical system includes at least one of (a) an optical communication system and (b) a light detection and ranging (LIDAR) system.

14. A first beam splitter configured to split a first beam into a high-power portion and a low-power portion of the first beam, A second beam splitter configured to split a second beam into a high-power portion and a low-power portion of the second beam, A combiner configured to combine a low-power portion of the first beam and a low-power portion of the second beam in order to generate a heterodyne beam, The frequency of the first beam is shifted relative to the frequency of the second beam, A laser system in which the heterodyne frequency of the heterodyne beam represents the phase noise between the low-power portion of the first beam and the low-power portion of the second beam, and the phase noise between the low-power portion of the first beam and the low-power portion of the second beam is used to reduce the phase error between the high-power portion of the first beam and the high-power portion of the second beam.

15. A photodetector configured to detect a heterodyne beam having the heterodyne frequency and to generate a detected heterodyne signal by detecting the heterodyne beam, wherein the detected heterodyne signal includes the phase noise between the low-power portion of the first beam and the low-power portion of the second beam, and the detected phase noise generated by the photodetector when detecting the heterodyne beam. A detection phase noise reduction circuit configured to reduce the detection phase noise of the detection heterodyne signal, The laser system according to claim 14, further comprising a modulator configured to correct a phase error between the high-power portion of the first beam and the high-power portion of the second beam using the detection heterodyne signal and the reduction of the detection phase noise.

16. A fourth signal generator configured to generate a fourth signal generator output, the fourth signal generator being a voltage control signal generator, A fourth mixer is configured to mix the output of the fourth signal generator with the output of a high-frequency oscillator in order to generate a fourth mixer output signal, A fifth mixer is configured to mix the fourth mixer output signal with a detection heterodyne signal in order to generate a fifth mixer output signal, A fifth signal generator configured to generate a fifth signal generator output, A sixth mixer is configured to mix the output of the fifth signal generator with the fifth mixer output signal in order to generate a sixth mixer output signal, A servo loop filter configured to receive the sixth mixer output signal and generate a control signal using the sixth mixer output signal, wherein the control signal frequency modulates the fourth signal generator to generate a modulated fourth signal generator output. A sixth signal generator configured to generate a sixth signal generator output, A seventh mixer is configured to mix the modulated output of the fourth signal generator with the output of the sixth signal generator in order to generate a seventh mixer output signal, A first acousto-optic modulator configured to correct the phase error between the high-power portion of the first beam and the high-power portion of the second beam by modulating the high-power portion of the first beam using the seventh mixer output signal, or a second acousto-optic modulator configured to correct the phase error between the high-power portion of the first beam and the high-power portion of the second beam by modulating the high-power portion of the second beam using the seventh mixer output signal, The laser system according to claim 14, comprising a radio frequency switch electronically coupled to the seventh mixer and the acousto-optic modulator, the radio frequency switch configured to switch on or off the modulation by the acousto-optic modulator using the output signal of the seventh mixer.

17. A fifth signal generator configured to generate a fifth signal generator output, A fourth mixer is configured to mix the output of the fifth signal generator with the output of a high-frequency oscillator in order to generate a fourth mixer output signal, A fifth mixer is configured to mix the fourth mixer output signal with a detection heterodyne signal in order to generate a fifth mixer output signal, A sixth signal generator configured to generate a sixth signal generator output, A seventh mixer is configured to mix the fifth mixer output signal with the sixth signal generator output signal in order to generate a seventh mixer output signal, A first acousto-optic modulator configured to correct the phase error between the high-power portion of the first beam and the high-power portion of the second beam by modulating the high-power portion of the first beam using the seventh mixer output signal, or a second acousto-optic modulator configured to correct the phase error between the high-power portion of the first beam and the high-power portion of the second beam by modulating the high-power portion of the second beam using the seventh mixer output signal, The laser system according to claim 14, comprising a radio frequency switch electronically coupled to the seventh mixer and the acousto-optic modulator, the radio frequency switch configured to switch the modulation by the acousto-optic modulator on or off using the output signal of the seventh mixer.

18. The laser system according to claim 14, wherein the high-power portion of the first beam and the high-power portion of the second beam perform at least one of (a) entanglement of qubits in a quantum computer and (b) providing a first laser light source and a second laser light source to a coherent heterodyne optical system.

19. The laser system according to claim 14, wherein the high-power portion of the first beam and the high-power portion of the second beam are configured to provide a first laser light source and a second laser light source to a coherent heterodyne optical system, and the coherent heterodyne optical system includes either an optical communication system or a light detection and ranging (LIDAR) system.

20. A method for reducing phase noise between optical beams, The steps include splitting the first beam into a high-power portion and a low-power portion of the first beam, A step of splitting a second beam into a high-power portion and a low-power portion of the second beam, wherein the frequency of the first beam is shifted relative to the frequency of the second beam. The steps include generating a sideband of the low-power portion of the first beam at an offset frequency from the frequency of the low-power portion of the second beam, A method comprising the step of reducing the phase error between the high-power portion of the first beam and the high-power portion of the second beam by using the phase noise between the sideband of the low-power portion of the first beam and the low-power portion of the second beam.

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