ELECTRO-OPTICALLY INDUCED WEAK COUPLING OF ADJACENT CARBON DIOXIDE LASER MODES

• US 3,790,901 A
• Filed: 03/22/1972
• Issued: 02/05/1974
• Est. Priority Date: 03/22/1972
• Status: Expired due to Term

• Current Assignee: Loral Aerospace Corp. (MHR Holdings LLC (New York))
• Original Assignee: Matthew B. White, Wesley Duane Gerber
• Inventors: White, Matthew B., Gerber, Wesley Duane
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Webster, R. J.
• Application Number:
  US05/237,038
• Time in Patent Office: 685 Days
• Field of Search: 331/94.5 250/199 350/150,160
• US Class Current: 372/19
• CPC Class Codes: H01S 3/107 using electro-optic devices, e.g. exhibiting Pockels or Kerr effect H01S3/1061, H01S3/1063, H01S3/1065 take precedence
• CPC Class Codes: H01S 3/136 by controlling devices placed within the cavity

Abstract

A low level polarization modulation is applied to a carbon dioxide dual-polarization laser. The modulation frequency is approximately equal to the difference in frequency between allowed orthogonally polarized adjacent laser modes. This modulation insures dual-polarization operation in the carbon dioxide laser, which, in the absence of such modulation, will only oscillate in one mode. Adjacent mode coupling is ordinarily so strong that the oscillating mode suppresses the adjacent mode. Since the polarization modulation offsets the adjacent mode coupling it is called electro-optically induced weak coupling or EIWC.

Claims

1. A laser comprising:

an optical resonator, linear birefringence means inside said resonator for producing dual polarization operating modes, an active medium located inside said resonator, said medium characterized by strong coupling between closely spaced oscillating modes, means for pumping said active medium, means for extracting optical energy from said resonator, and means located inside said resonator for inducing dual polarization operation by polarization modulation of optical energy in said resonator at a frequency approximately equal to the frequency difference of said dual polarization modes.

2. The laser of claim 1 wherein said last-named means comprises:

electrically variable birefringence means having a birefringence axis that is located at an angle with respect to the birefringence axis of said linear birefringence means, and means for applying an electrical signal to said electrically variable birefringence means, said electrical signal having a frequency of approximately the difference in frequency between said dual polarization modes.

3. The laser of claim 2 wherein said angle is about 45*.

4. The laser of claim 2 wherein said electrical signal has an amplitude slightly in excess of that value necessary to induce dual polarization operation of said laser.

5. A laser as claimed in claim 1 wherein said active medium comprises carbon dioxide.

6. In a dual polarization laser having an optical resonator, an active medium located inside said resonator, pumping means associated with said active medium, said active medium when pumped by said pumping means acting to provide the amplification for laser action, said active medium comprising a laser material characterized by such strong coupling between allowed othogonally polarized adjacent laser modes that the oscillating mode tends to suppress the adjacent mode, linear birefringence means inside said resonator to establish dual polarization operating modes of said laser, and means for extracting optical energy from said resonator, the improvement comprising:

apparatus for inducing dual polarization operation of said laser by modulating the polarization affected by said linear birefringence means at a frequency approximating the difference between said adjacent laser modes.

7. The improvement of claim 6 wherein said active medium comprises carbon dioxide.

8. The improvement of claim 6 wherein said apparatus comprises:

electrically variable birefringence means having a birefringence axis oriented at an angle with respect to the birefringence axis of said linear birefringence means, and means for applying an electrical signal to said electrically variable birefringence means at a frequency approximating that of the dual polarization mode separation.

9. The improvement of claim 8 wherein said angle is about 45*.