External laser frequency stabilizer

• US 4,700,150 A
• Filed: 06/14/1985
• Issued: 10/13/1987
• Est. Priority Date: 06/14/1985
• Status: Expired due to Fees

• Current Assignee: Government of the United States of America, Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Stanford University
• Inventors: Hall, John L., Hansch, Theodor W.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US06/745,309
• Time in Patent Office: 851 Days
• Field of Search: 332/7.51, 350/355, 350/358, 307/425, 307/427, 372/18, 372/20, 372/29, 372/32
• US Class Current: 359/279
• CPC Class Codes: G02F 1/03 based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect G02F1/061 takes precedence
• CPC Class Codes: G02F 1/113 Circuit or control arrangements
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B

Abstract

An external laser frequency stabilizer combines an acousto-optic frequency shifter and a fast electro-optic phase modulator. A compensating electronic delay line in a crossover network provides a near-ideal transducer response while keeping the voltage across the electro-optic crystal away from the amplifier limits.

Claims

1. A frequency transducer for controlling or modulating the frequency of a light radiation system comprising:

a source of radiation having a predetermined frequency;

an electro-optic phase modulator for receiving said radiation and for changing the phase of said radiation in proportion to an applied error voltage;

an acousto-optic modulator coupled to said electro-optic modulator for shifting the frequency of the output signal of said electro-optic modulator;

a signal source for providing an error voltage representing undesirable fluctuations in the frequency of said light radiation;

a first channel including a fast integrator coupled between said signal source and the input circuit of said electro-optic modulator;

a second channel including a voltage controlled oscillator coupled between said signal source and said acousto-optic modulator; and

a network including an electronic delay circuit coupled between said first and second channels for matching the delay of the acousto-optic modulator.

2. A frequency transducer as in claim 1, wherein said network further includes an inverting amplifier and a low pass filter connected in parallel and coupled to said delay circuit and to the input circuit of said voltage controlled oscillator.

3. A frequency transducer as in claim 2, wherein said delay circuit is coupled in a closed feedback loop to the input circuit and output circuit of said fast integrator.

4. A frequency transducer as in claim 1, wherein said delay circuit comprises analog delay means.

5. A frequency transducer as in claim 1, wherein said acousto-optic modulator utilizes tellurium dioxide, or lead molybdate.