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

Patent metadata

Field	Value
Publication number	US-2016254646-A1
Application number	US-201615053876-A
Country	US
Kind code	A1
Filing date	Feb 25, 2016
Priority date	Feb 26, 2015
Publication date	Sep 1, 2016
Grant date	—

Abstract

Microwave-frequency signal generation by generating multiple sideband optical signals separated by phase-modulation frequency f M , 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 M . A portion of the VCO output is the generated microwave-frequency signal.

First claim

What is claimed is:

1 . A microwave-frequency source for generating an output electrical signal at an output frequency f M , the microwave-frequency source comprising:
(a) a dual optical-frequency reference source arranged so as to generate (i) a first optical reference signal at a first optical reference frequency v 1 and (ii) a second optical reference signal at a second optical reference frequency v 2 >v 1 ; (b) an electro-optic sideband generator arranged so as to (i) receive a third optical reference signal at a third optical reference frequency v 0 and a sideband generator input electrical signal at the frequency f M and (ii) generate therefrom multiple sideband optical signals at respective sideband optical frequencies of the form v 0 ±nf M , wherein n is an integer; (c) one or both of (i) a first optical bandpass filter arranged so as to transmit the first optical reference signal and a subset of the multiple sideband optical signals including the sideband optical signal at a frequency v 0 −N 1 f M , wherein N 1 is an integer, or (ii) a second optical bandpass filter arranged so as to transmit the second optical reference signal and a subset of the multiple sideband optical signals including the sideband optical signal at a frequency v 0 +N 2 f M , wherein N 2 is an integer; (d) one or both of (i) a first optical detector arranged so as to receive the optical signals transmitted by the first optical bandpass filter and to generate therefrom a first optical detector electrical signal at a first beat frequency f BEAT1 =|v 1 −(v 0 −N 1 f M )|, or (ii) a second optical detector arranged so as to receive the optical signals transmitted by the second optical bandpass filter and to generate therefrom a second optical detector electrical signal at a second beat frequency f BEAT2 =|v 2 −(v 0 +N 2 f M )|; (e) a reference oscillator arranged so as to generate a reference oscillator electrical signal at a reference oscillator frequency f R ; (f) an electrical circuit arranged so as to (i) receive the reference oscillator electrical signal and only one of (A) the first optical detector electrical signal, (B) the second optical detector electrical signal, or (C) a difference electrical signal generated from the first and second optical detector electrical signals by an electrical frequency mixer at an electrical difference frequency f DIFF =f BEAT2 −f BEAT1 =|v 2 −v 1 −(N 1 +N 2 )·f M |, (ii) generate therefrom, using a comparator portion of the electrical circuit, an electrical error signal dependent on relative phase of the electrical signals received by the electrical circuit, and (iii) process the electrical error signal using a loop-filter portion of the electrical circuit; and (g) a voltage-controlled electrical oscillator arranged so as to (i) receive the loop-filtered electrical error signal as a VCO input electrical signal and (ii) generate a VCO output electrical signal at the frequency f M , wherein a first portion of the VCO output electrical signal is received by the electro-optic sideband generator as the sideband generator input electrical signal and a second portion of the VCO output electrical signal forms the output electrical signal of the microwave-frequency source, (h) wherein reception of the first portion of the VCO output electrical signal by the electro-optic sideband generator as the sideband generator input electrical signal results in the electrical circuit and the voltage-controlled oscillator being coupled in a negative feedback arrangement so as to function as a phase-locked loop.

2 . The microwave-frequency source of claim 1 wherein:
(b′) the third optical reference frequency v 0 differs from the first optical reference frequency v 1 and from the second optical reference frequency v 2 ;
(c′) the first optical bandpass filter is arranged so as to transmit the first optical reference signal and a subset of the multiple sideband optical signals including the sideband optical signal at the frequency v 0 −N 1 f M , and the second optical bandpass filter is arranged so as to transmit the second optical reference signal and a subset of the multiple sideband optical signals including the sideband optical signal at the frequency v 0 +N 2 f M ;
(d′) the first optical detector arranged so as to receive the optical signals transmitted by the first optical bandpass filter and to generate therefrom the first optical detector electrical signal at the first beat frequency f BEAT =|v 1 −(v 0 −N 1 f M )|, and the second optical detector arranged so as to receive the optical signals transmitted by the second optical bandpass sideband optical signals and to generate therefrom the second optical detector electrical signal at the second beat frequency f BEAT1 =|v 2 −(v 0 +N 2 f M )|; and
(f′) the electrical circuit is arranged so as to (i) receive the reference oscillator electrical signal and the difference electrical signal at the electrical difference frequency f DIFF =f BEAT2 −f BEAT1 =|v 2 −v 1 −(N 1 +N 2 )·f M |, and (ii) generate therefrom, using the comparator portion of the electrical circuit, the electrical error signal dependent on the relative phase of the reference oscillator electrical signal and the difference electrical signal received by the electrical circuit, and (iii) process the electrical error signal using the loop-filter portion of the electrical circuit.

3 . The microwave-frequency source of claim 2 wherein phase noise of the output electrical signal of the microwave-frequency source is reduced by a factor of about (N 1 +N 2 ) 2 relative to phase noise of a reference difference frequency signal at a reference optical difference frequency v 2 −v 1 of the dual optical-frequency reference source.

4 . The microwave-frequency source of claim 1 wherein:
(b′) the electro-optic sideband generator is arranged so as to (i) receive a portion of the first optical reference signal as the third optical reference signal so that v 0 =v 1 and (ii) generate therefrom multiple sideband optical signals at respective sideband optical frequencies of the form v 1 ±nf M , wherein n is an integer;
(c′) the second optical bandpass filter is arranged so as to transmit the second optical reference signal and a subset of the multiple sideband optical signals including the sideband optical signal at a frequency v 1 +N 2 f M ;
(d′) the second optical detector is arranged so as to receive the optical signals transmitted by the second optical bandpass filter and to generate therefrom the second optical detector electrical signal at the second beat frequency f BEAT2 =|v 2 −(+N 2 f M )|; and
(f′) the electrical circuit is arranged so as to (i) receive the reference oscillator electrical signal and the second optical detector electrical signal, and (ii) generate therefrom, using the comparator portion of the electrical circuit, the electrical error signal dependent on the relative phase of the reference oscillator electrical signal and the second optical detector electrical signal received by the electrical circuit, and (iii) process the electrical error signal using the loop-filter portion of the electrical circuit.

5 . The microwave-frequency source of claim 4 wherein phase noise of the output electrical signal of the microwave-frequency source is reduced by a factor of about (N 2 ) 2 relative to phase noise of a reference difference frequency signal at a reference optical difference frequency v 2 −v 1 of the dual optical-frequency reference source.

6 . The microwave-frequency source of claim 1 wherein:
(b′) the electro-optic sideband generator is arranged so as to (i) receive a portion of the second optical reference signal as the third optical reference signal so that v 0 =v 2 and (ii) generate therefrom multiple sideband optical signals at respective sideband optical f

Assignees

• California Inst Of Techn

Inventors

• Li Jiang
• Vahala Kerry

Classifications

• H01S5/0687 Primary

  Stabilising the frequency of the laser · CPC title

• H01S5/06817

  Noise reduction · CPC title

• H01S5/40

  Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30 (H01S5/50 takes precedence) · CPC title

• H01S5/041

  Optical pumping · CPC title

• H01S5/0078

  for frequency filtering · CPC title