Method and apparatus for generating optical frequency comb

1. A method for generating an optical frequency comb, comprising:

receiving a pump laser that matches a thermally stable state of a nonlinear optical resonant cavity and causing the pump laser to oscillate in the nonlinear optical resonant cavity;

adjusting the nonlinear optical resonant cavity, such that a Brillouin gain corresponding to the pump laser coincides with a target longitudinal mode in the nonlinear optical resonant cavity;

continuously generating Brillouin laser at the target longitudinal mode in the case that a pump power of the pump laser exceeds a threshold for generating the Brillouin laser; and

generating an optical frequency comb including optical solitons by using the Brillouin laser through a Kerr nonlinear four-wave mixing process.

2. The generation method according to claim 1 , wherein the step of adjusting the nonlinear optical resonant cavity, such that the Brillouin gain corresponding to the pump laser coincides with the target longitudinal mode in the nonlinear optical resonant cavity comprises:

adjusting a cavity length of the nonlinear optical resonant cavity so as to adjust a position of the target longitudinal mode, such that the target longitudinal mode coincides with the Brillouin gain.

3. The generation method according to claim 1 , wherein the step of adjusting the nonlinear optical resonant cavity, such that the Brillouin gain corresponding to the pump laser coincides with the target longitudinal mode in the nonlinear optical resonant cavity further comprises:

changing a stress applied by the nonlinear optical resonant cavity so as to adjust a position of the Brillouin gain, such that the Brillouin gain coincides with the target longitudinal mode, wherein the stress is adjusted by twisting a cavity body of the nonlinear optical resonant cavity, and a twisting angle is in the range of 0° to 180°.

4. The generation method according to claim 1 , wherein the step of adjusting the nonlinear optical resonant cavity, such that the Brillouin gain corresponding to the pump laser coincides with the target longitudinal mode in the nonlinear optical resonant cavity further comprises:

changing a temperature of the nonlinear optical resonant cavity so as to adjust the position of the Brillouin gain, such that the Brillouin gain coincides with the target longitudinal mode, wherein a temperature adjustment range is −10° C. to +90° C.

5. The generation method according to claim 1 , wherein the Brillouin gain corresponding to the pump laser is caused to coincide with the target longitudinal mode in the nonlinear optical resonant cavity by adjusting a wavelength of the pump laser, wherein an adjustment range of the wavelength of the pump laser is 1540 nm to 1565 nm.

6. The generation method according to claim 1 , wherein the generated optical frequency comb has discrete spectra which are arranged at equal frequency intervals, wherein the optical frequency comb is generated under a thermally stable state of the nonlinear optical resonant cavity, and excited by the Brillouin laser through a Kerr effect.

7. The generation method according to claim 1 , wherein a linewidth of a single comb tooth of the generated optical frequency comb is smaller than a linewidth of the pump laser.

8. The generation method according to claim 1 , wherein a noise of the generated optical frequency comb reaches a quantum noise limit corresponding to a nonlinear microcavity without active control.

9. An apparatus for generating an optical frequency comb, comprising:

a pumping source, configured to emit a continuous pump laser to a nonlinear optical resonant cavity; wherein the pumping source changes a wavelength of the pump laser in a controlled manner, such that the wavelength of the pump laser matches a thermally stable state of the nonlinear optical resonant cavity, and that the pump laser oscillates in the thermally stable state of the nonlinear optical resonant cavity and is emitted from the nonlinear optical resonant cavity; and

the nonlinear optical resonant cavity, configured to align the received pump laser to a certain longitudinal mode in a first set of longitudinal modes in the nonlinear optical resonant cavity; wherein the nonlinear optical resonant cavity changes a position of a Brillouin gain corresponding to the pump laser or changes a position of a target longitudinal mode in a second set of longitudinal modes in the nonlinear optical resonant cavity in a controlled manner, such that the Brillouin gain coincides with the target longitudinal mode; and wherein the nonlinear optical resonant cavity continuously generates a Brillouin laser at the target longitudinal mode in the case that a pump power of the pump laser exceeds a threshold for generating the Brillouin laser; and wherein the Brillouin laser generates the optical frequency comb through a Kerr nonlinear four-wave mixing process.

10. The generation apparatus according to claim 9 , wherein the nonlinear optical resonant cavity is an optical resonant cavity having both Brillouin nonlinearity and Kerr nonlinearity.

11. The generation apparatus according to claim 9 , wherein the nonlinear optical resonant cavity is one of a traveling wave resonant cavity or a standing wave resonant cavity.

12. The generation apparatus according to claim 9 , wherein the longitudinal modes in the nonlinear optical resonant cavity are introduced by different polarization modes of the nonlinear optical resonant cavity or by transverse modes of different orders.

13. The generation apparatus according to claim 9 , wherein at least one set of longitudinal mode exists in the nonlinear optical resonant cavity.