California Institute of Technology

Government of the United States of America, As Represented by the Secretary of Commerce

Hqphotonics Inc.

Jiang Li

Kerry J Vahala

Hansuek Lee

Tong Chen

Scott A Diddams

Xu Yi

Myoung-Gyun Suh

Seung Hoon Lee

Yu-Hung Lai

Scott Diddams

A disk resonator is pumped by counterpropagating pump signals to produce corresponding counterpropagating Brillouin laser signals. The pump laser optical frequencies are separated by a frequency offset &#x394;&#x3bd;but excite the same nominal resonator optical mode; the Brillouin laser optical frequencies are separated by a beat frequency &#x394;&#x3bd;with 0&#x3c;&#x394;&#x3bd;&#x3c;&#x394;&#x3bd;. A photodetector receives the Brillouin laser signals and produces an electrical signal at the beat frequency &#x394;&#x3bd;. The frequency offset &#x394;&#x3bd;can be large so enough to prevent locking of the Brillouin laser signals onto a common Brillouin laser frequency. A signal processing system derives from the beat frequency &#x394;&#x3bd;an estimated angular velocity component of the disk optical resonator about an axis substantially perpendicular to the disk optical resonator.

Stimulated brillouin ring laser gyroscope with optical frequency offset of counterpropagating pump laser signals

A voltage-controlled oscillator generates a VCO output signal at frequency f. A dual optical-frequency source generates optical signals at frequencies vand v. An electro-optic frequency divider (EOFD) generates multiple optical sidebands spaced by f, and from two sidebands generates a beat signal at beat frequency &#x3b4;f. A first control circuit generates an error signal from the beat signal and a first reference signal at frequency f, and couples the VCO and the EOFD in a negative feedback arrangement that stabilizes the output frequency f. A second control circuit generates an error signal from the frequency-divided output signal and a second reference signal at frequency f, and couples the VCO and one or both of the dual source or the first reference signal in a negative feedback arrangement that stabilizes, or compensates for fluctuations of, a difference frequency v&#x2212;v.

Stabilized microwave-frequency source

A stabilized laser source includes a fiber-ring Brillouin laser that incorporates a circulator for non-reciprocal operation and for launching of a pump optical signal. Most of the pump optical signal is launched in a forward direction and drives Brillouin laser oscillation in the backward direction, a portion of which exits via an optical coupler as the optical output of the laser source. A small fraction of the pump optical signal is launched in the backward direction via the optical coupler, and a fraction of that backward-propagating pump optical signal exits via the optical coupler as an optical feedback signal. A frequency-locking mechanism receives the optical feedback signal and controls the pump optical frequency to maintain resonant propagation of the backward-propagating pump optical signal. A second pump optical signal can be launched in the forward direction to generate a second Brillouin laser oscillation.

Stabilized non-reciprocal fiber-ring brillouin laser source

A microwave-frequency source at frequency fcomprises: a dual optical-frequency reference source, an electro-optic sideband generator, an optical bandpass filter, an optical detector, a reference oscillator, an electrical circuit, and a voltage-controlled oscillator (VCO). The sideband generator modulates dual optical reference signals at vand vto generate sideband signals at v&#xb1;nfand v&#xb1;nf. The bandpass filter transmits sideband signals at v+Nfand v&#x2212;Nf. The optical detector generates a beat note at (v&#x2212;Nf)&#x2212;(v+Nf). The beat note and a reference oscillator signal are processed by the circuit to generate a loop-filtered error signal to input to the VCO. Output of the VCO at fdrives the sideband generator and forms the microwave-frequency output signal. The resultant frequency division results in reduced phase noise on the microwave-frequency signal.

Microwave-frequency signal generation by generating multiple sideband optical signals separated by phase-modulation frequency f, generating beat signals between one or two sidebands and one or two optical reference signals, generating a loop-filtered error signal by comparing an electrical reference signal to one of the beat signals or their difference, and controlling with the error signal in a phase-locked loop arrangement a voltage-controlled oscillator (VCO) that drives the sideband generation at the frequency f. A portion of the VCO output is the generated microwave-frequency signal.

Optical frequency divider based on an electro-optical-modulator frequency comb

A microwave-frequency source, generating an output electrical signal at an output frequency f, comprises a pump laser source, an optical resonator, and a photodetector. Free spectral range vof the optical resonator equals an integer submultiple of a Brillouin shift frequency vof the optical resonator (i.e., v=Mv). The pump laser source is frequency-locked to a corresponding resonant optical mode of the optical resonator. Pumping the optical resonator with output of the pump laser source at a pump frequency vresults in stimulated Brillouin laser oscillation in the optical resonator at respective first, second, and third Stokes Brillouin-shifted frequencies v=v&#x2212;v, v=v&#x2212;2v, and v=v&#x2212;3v. The photodetector receives stimulated Brillouin laser outputs at the first and third Stokes Brillouin-shifted frequencies vand vand generates therefrom the output electrical signal at a beat frequency f=v&#x2212;v=2v. The output electrical signal at the output frequency fexhibits exceptionally low phase noise.

Stable microwave-frequency source based on cascaded brillouin lasers

A dual-frequency optical source comprises: (a) first and second pump laser sources arranged to generate optical pump power at respective first and second pump laser frequencies vand v; and (b) a fiber optical resonator characterized by a Brillouin shift frequency vand a free spectral range that is substantially equal to an integer submultiple of the Brillouin shift frequency. Each one of the first and second pump laser sources is frequency-locked to a corresponding resonant optical mode of the fiber optical resonator. First and second optical output signals of the dual-frequency optical reference source at respective first and second output frequencies v=v&#x2212;vand v=v&#x2212;vcomprise stimulated Brillouin laser output generated by simultaneous optical pumping of the fiber optical resonator by the first and second pump laser sources, respectively. An output difference frequency v&#x2212;vis greater than about 300 GHz.

Dual-frequency optical source

A highly-coherent chip-based laser generating system includes a disk resonator incorporating a wedge structure fabricated from a silicon dioxide layer of a chip. The disk resonator is operable to generate a highly-coherent laser from a low-coherence optical pump input provided at an optical power level as low as 60 &#x3bc;W. The disk resonator is fabricated with sub-micron cavity size control that allows generation of a highly-coherent laser using a controllable Stimulated Brillouin Scattering process that includes matching of a cavity free-spectral-range to a Brillouin shift frequency in silica. While providing several advantages due to fabrication on a chip, the highly-coherent laser produced by the disk resonator may feature a Schawlow-Townes noise level as low as 0.06 Hz/Hz (measured with the coherent laser at a power level of about 400 &#x3bc;W) and a technical noise that is at least 30 dB lower than the low-coherence optical pump input.

Chip-based laser resonator device for highly coherent laser generation

A frequency comb generator fabricated on a chip with elimination of a disadvantageous reflow process, includes an ultra-high Q disk resonator having a waveguide that is a part of a wedge structure fabricated from a silicon dioxide layer of the chip. The disk resonator allows generation of a frequency comb with a mode spacing as low as 2.6 GHz and up to 220 GHz. A surface-loss-limited behavior of the disk resonator decouples a strong dependence of pumping threshold on repetition rate.

Chip-based frequency comb generator with microwave repetition rate

A method of manufacturing a waveguide eliminates a prior art reflow step and introduces certain new steps that permit fabricating of an ultra-low loss waveguide element on a silicon chip. The ultra-low loss waveguide element may be adapted to fabricate a number of devices, including a wedge resonator and a ultra-low loss optical delay line having an extended waveguide length.

Growing community of inventors

Pasadena, CA, United States of America

Jiang Li