Laser intra-cavity electronic wavelength tuner

• US 20070280310A1
• Filed: 06/02/2006
• Published: 12/06/2007
• Est. Priority Date: 06/02/2006
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Muenter, Steven E., Seiden, Harold N.
• Granted Patent: US 7,564,880 B2
• Time in Patent Office: Days
• US Class Current: 372/28
• CPC Class Codes: H01S 3/0816 having 4 reflectors, e.g. Z-shaped resonators
• CPC Class Codes: H01S 3/082 defining a plurality of resonators, e.g. for mode selection or suppression
• CPC Class Codes: H01S 3/1068 using an acousto-optical device
• CPC Class Codes: H01S 3/2207 Noble gas ions, e.g. Ar+>, Kr+>

Abstract

An apparatus for adjusting the wavelength of a laser capable of lasing at multiple wavelengths by using a single acousto-optical modulator and a pair of optical reflectors inside a laser cavity. By adjusting the frequency and amplitude of the radio-frequency source to the acousto-optical modulator, undesired wavelengths are suppressed in the laser cavity, leaving appreciable gain only at the desired wavelength.

Claims

1. A wavelength-adjustable laser, comprising:

a. a gain medium for amplifying a laser beam in a wavelength range;

b. a first optical reflector;

c. an acousto-optical modulator located between the gain medium and the first optical reflector such that the acousto-optical modulator diffracts a portion of the laser beam into a plurality of diffracted laser beams wherein each diffracted laser beam diffracts at a different angle from an optical axis formed by the laser beam based on the wavelength of the diffracted laser beam;

d. a second optical reflector and a third optical reflector positioned about the optical axis such that only a selected diffracted laser beam from the plurality of diffracted laser beams is reflected off both the second optical reflector and the third optical reflector into the acousto-optical modulator; and

e. an adjustable radio-frequency source coupled to the acousto-optical modulator wherein the wavelength of the selected diffracted laser beam is changed by adjusting the frequency of a radio signal emitted from the adjustable radio-frequency source.

2. The wavelength-adjustable laser of claim 1 wherein the amount of light diffracted by the acousto-optical modulator varies with adjustment of the amplitude of the radio signal emitted from the adjustable radio-frequency source.

3. The wavelength-adjustable laser of claim 1 including an output coupler positioned on the opposite side of the gain medium as the acousto-optical modulator.

4. The wavelength-adjustable laser of claim 1 wherein the first optical reflector is an output coupler.

5. The wavelength-adjustable laser of claim 1 wherein the acousto-optical modulator is a Bragg cell.

6. The wavelength-adjustable laser of claim 1 wherein the second optical reflector and the third optical reflector are positioned symmetrically about the optical axis.

7. The wavelength-adjustable laser of claim 1 wherein the optical path length from the acousto-optical modulator to the first optical reflector and back to the acousto-optical reflector is equal to the optical path length from the acousto-optical modulator to the second optical reflector to the third optical reflector to the acousto-optical reflector.

8. The wavelength-adjustable laser of claim 1 wherein the position of the first optical reflector relative to the acousto-optical modulator is adjustable.

9. The wavelength-adjustable laser of claim 1 wherein the radio signal emitted from the adjustable radio-frequency source comprises a first radio-frequency signal and a second radio-frequency signal.

10. The wavelength-adjustable laser of claim 9 wherein the selected diffracted laser beam comprises a first wavelength diffracted laser beam and a second wavelength diffracted laser beam.

11. The wavelength-adjustable laser of claim 10 wherein:

a. the wavelength of the first wavelength diffracted laser beam is changed by adjusting the frequency of the first radio-frequency signal; and

b. the wavelength of the second wavelength diffracted laser beam is changed by adjusting the frequency of the second radio-frequency signal.

12. A method for adjusting the wavelength of a laser, comprising the steps of:

a. positioning an acousto-optical modulator between a gain medium and a first optical reflector;

b. coupling an adjustable radio-frequency source to the acousto-optical modulator; and

c. positioning a second optical reflector and a third optical reflector about an optical axis formed by an undiffracted laser beam coming from the acousto-optical modulator.

13. The method of claim 12 further comprising positioning the second optical reflector and the third optical reflector such that only a selected wavelength of a diffracted laser beam coming from the acousto-optical modulator reflects off the second optical reflector and the third optical reflector into the acousto-optical modulator.

14. The method of claim 12 further comprising positioning the second optical reflector and the third optical reflector symmetrically about the optical axis.

15. The method of claim 12 further comprising adjusting the frequency of a radio signal emitted from the radio-frequency source to adjust the wavelength of the laser.

16. The method of claim 12 further comprising adjusting the amplitude of a radio signal emitted from the radio-frequency source to vary the amount of light diffracted by the acousto-optical modulator.

17. The method of claim 12 further comprising positioning an output coupler such that the gain medium lies between the output coupler and the acousto-optical modulator.

18. The method of claim 12 wherein the step of positioning the acousto-optical modulator includes positioning a Bragg cell.

19. The method of claim 12 further comprising positioning the first optical reflector such that the optical path length from the acousto-optical modulator to the first optical reflector back to the acousto-optical reflector is equal to the optical path length from the acousto-optical modulator to the second optical reflector to the third optical reflector to the acousto-optical reflector.

20. The method of claim 12 further comprising adjusting the distance between the first optical reflector and the acousto-optical modulator.

21. The method of claim 12 further comprising emitting a first radio-frequency signal and a second radio-frequency signal from the adjustable radio-frequency source to the acousto-optical modulator.

22. The method of claim 21 further comprising selecting the frequency of the first radio-frequency signal and the frequency of the second radio-frequency signal such that two different wavelengths of the laser reflect off of the second optical reflector and the third optical reflector into the acousto-optical modulator.