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Resonant phase modulator

  • US 4,998,255 A
  • Filed: 10/11/1989
  • Issued: 03/05/1991
  • Est. Priority Date: 10/11/1989
  • Status: Expired due to Fees
First Claim
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1. Light beam modulation apparatus for varying the optical phases of a light beam output signal relative to the optical phase of a light beam input signal, the apparatus comprising:

  • an optically resonant electro-optical crystal, having a first partially transmissive crystal face to receive a light beam having a frequency-stabilized single frequency and to cause a portion of the light beam to propagate internally within the crystal, and having at least second and third crystal faces positioned to reflect this internally propagating portion of the beam so that this portion follows a closed path within the crystal with a phase shift φ

    that varies around a resonant value φ

    r =2Nπ

    , where N is a non-zero integer, along this closed path, where a portion of this internally propagating portion of the light beam that arrives at the first crystal face combines with an externally reflected portion of the light beam to form an output beam propagating in a selected direction; and

    a voltage source positioned adjacent to the crystal to impress a controllable, time-varying voltage deference across the crystal in a second selected direction to controllably vary the phase shift φ

    about the resonant value φ

    r =2Nπ

    .

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