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

  • US 9,905,999 B2
  • Filed: 02/25/2016
  • Issued: 02/27/2018
  • Est. Priority Date: 02/26/2015
  • Status: Active Grant
First Claim
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1. A microwave-frequency source for generating an output electrical signal at an output frequency fM, 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 v1 and (ii) a second optical reference signal at a second optical reference frequency v2>

    v1;

    (b) an electro-optic sideband generator arranged so as to (i) receive a third optical reference signal at a third optical reference frequency v0 and a sideband generator input electrical signal at the frequency fM and (ii) generate therefrom multiple sideband optical signals at respective sideband optical frequencies of the form v0±

    nfM, 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 v0

    N1fM, wherein N1 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 v0+N2fM, wherein N2 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 fBEAT1=|v1

    (v0

    N1fM)|, 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 fBEAT2=|v2

    (v0+N2fM)|;

    (e) a reference oscillator arranged so as to generate a reference oscillator electrical signal at a reference oscillator frequency fR;

    (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 fDIFF=fBEAT2

    fBEAT1=|v2

    v1

    (N1+N2

    fM|, (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 fM, 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.

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