METHOD FOR WIDEBAND SPECTRALLY EQUALIZED FREQUENCY COMB GENERATION

• US 20140254619A1
• Filed: 03/11/2014
• Published: 09/11/2014
• Est. Priority Date: 03/11/2013
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Stojan Radic
• Inventors: ATAIE, Vahid, RADIC, Stojan
• Granted Patent: US 9,106,325 B2
• Time in Patent Office: Days
• US Class Current: 372/28
• CPC Class Codes: H01S 5/0057 for temporal shaping, e.g. pulse compression, frequency chirping
• CPC Class Codes: H01S 5/0085 for modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 5/0092 for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
• CPC Class Codes: H04B 10/00 Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
• CPC Class Codes: H04B 10/506 Multiwavelength transmitters

Abstract

The present invention relates to method for spectrally equalized frequency comb generation. In order to carry this method, the following steps are followed: seed laser or lasers are modulated to acquire frequency chirp necessary to enable temporal compression and an increase in peak optical intensity necessary for an efficient nonlinear optical mixing process to occur; the compressed waveform is reshaped by nonlinear-transfer optical element and subsequently used to generate frequency comb in nonlinear waveguide. Ultimately, at the conclusion of these steps, a frequency comb is generated with substantially flat optical spectrum, while retaining variability with respect to the frequency pitch, high coherency and substantially wide spectral band of coverage.

Claims

1. A method for wideband frequency comb generation comprising:

(a) creating a seed waveform by modulating a single laser output;

(b) chirping the seed waveform created in step (a) to enable its temporal compression and peak intensity increase;

(c) compressing the chirped seed waveform in a dispersive waveguide in order to increase the intensity peak of the waveform and increase efficiency of mixing;

(d) employing a nonlinear optical transfer element that can discriminate the waveforms with respect to optical intensity; and

(e) mixing the waveforms to generate the frequency comb.

2. The method of claim 1 wherein frequency comb pitch does not exceed the bandwidth of an optical modulator.

3. The method of claim 1 wherein the waveform is chirped by nonlinear self-phase modulation in a nonlinear waveguide.

4. The method of claim 1 wherein the waveform is chirped by use of an optical modulator device.

5. The method of claim 1 wherein the nonlinear transfer element suppresses trailing (leading) sidelobes of the compressed waveform, allowing the single-peak waveform to seed the mixer stage and produce a spectrally equalized frequency comb.

6. The method of claim 1 wherein the nonlinear transfer element employs an optical loop mirror.

7. The method of claim 6 wherein the optical loop mirror provides simultaneous intensity discrimination, i.e., regeneration, and an additional waveform chirping function.

8. The method of claim 1 wherein more than one regeneration and compression stage is employed to control and increase the spectral flatness, coherency, power and bandwidth of the frequency comb generator.

9. The method of claim 1 wherein the laser is modulated using a phase modulator and an amplitude modulator to create the initial seed waveform.

10. The method of claim 1 wherein the frequency generator uses concatenated compression and regeneration sections to improve frequency comb performance.

11. The method of claim 1 wherein the method employs a frequency comb generator comprising chirping, compression, and mixing stages.

12. The method of claim 1 wherein the method employs a frequency comb generator comprising chirping, compression, regeneration, and mixing stages.

13. The method of claim 1 further employing intra-device amplification.

14. A method for wideband frequency comb generation comprising:

(a) creating a seed waveform by beating between two lasers;

(b) chirping the seed waveform created in step (a) to enable its temporal compression and peak intensity increase;

(c) compressing the chirped seed waveform in a dispersive waveguide in order to increase the intensity peak of the waveform and increase efficiency of mixing;

(d) employing a nonlinear optical transfer element that can discriminate the waveforms with respect to optical intensity; and

(e) mixing the waveforms to generate the frequency comb.

15. The method of claim 14 wherein the frequency comb pitch exceeds the bandwidth of a modulator device.

16. The method of claim 14 where the two lasers are free running.

17. The method of claim 14 wherein the two lasers are injection locked to a master to achieve phase correlation.