Acousto-optic tuning of lasers
A semiconductor laser tuned with an acousto-optic modulator. The acousto-optic modulator may generate standing waves or traveling waves. When traveling waves are used, a second acousto-optic modulator may be used in a reverse orientation to cancel out a chirp created in the first acousto-optic modulator. The acousto-optic modulator may be used with standing-wave laser resonators or ring lasers.
1. A laser, comprising:
a. a quantum cascade laser gain medium having a first end and a second end;
b. a first collimating lens adjacent to the first end of the gain and receiving an undiffracted beam from the gain medium, the undiffracted beam defining a first path;
c. an anti-reflection coating at the first end of the gain medium;
d. a first acousto-optic modulator configured to tune a laser wavelength across an entire gain curve, the first acousto-optic modulator adjacent to the first collimating lens and opposite the gain medium and fixed in place, the first acousto-optic modulator positioned to receive the undiffracted beam directly from the first collimating lens to subsequently emit a diffracted beam along a second path, wherein the first acousto-optic modulator is electronically controlled to produce the diffracted beam at a desired wavelength;
e. a first reflective mirror positioned to receive the diffracted beam and reflect the diffracted beam back along the second path to the first acousto-optic modulator through the first path and back to the gain medium to amplify a wavelength tuned beam; and
f. a second acousto-optic modulator between the first acousto-optic modulator and the first reflective mirror, wherein an orientation of the second acousto-optic modulator is reversed compared to the first acousto-optic modulator, and wherein the second acousto-optic modulator is electronically controlled to produce the diffracted beam at the desired wavelength.
2. The laser of claim 1 , further comprising a reflective coating at the second end of the gain medium.
3. The laser of claim 2 , wherein
a) the first acousto-optic modulator comprises a first end, a second end opposite the first end, and a first piezoelectric transducer at the first end of the first acousto-optic modulator;
b) the second acousto-optic modulator comprises a first end, a second end, and a second piezoelectric transducer at the first end of the second acousto-optic modulator;
c) a first radiofrequency generator for generating a first radiofrequency for controlling the first piezoelectric transducer; and
d) a second radiofrequency generator for generating a second radiofrequency for controlling the second piezoelectric transducer.
4. The laser of claim 3 , wherein
a) the first acousto-optic modulator comprises a first acoustic absorber at the second end of the first acousto-optic modulator; and
b) the second acousto-optic modulator comprises a second acoustic absorber at the second end of the second acousto-optic modulator.
5. The laser of claim 4 , wherein the laser is an infrared quantum cascade laser or an infrared interband cascade laser.
6. The laser of claim 2 , wherein the reflective coating is selected from the group consisting of a partially reflective coating and a highly reflective coating.
7. The laser of claim 1 , further comprising a second anti-reflection coating at the second end of the gain medium.
8. The laser of claim 1 , wherein the first acousto-optic modulator comprises:
a) a first end and a second end opposite the first end,
b) a first facet adjacent to the first and second ends, the first facet having a first anti-reflection coating at a desired optical wavelength, and
c) a second facet opposite the first facet and adjacent to the first and second ends, the second facet having a second anti-reflection coating at a desired optical wavelength.
9. The laser of claim 1 , further comprising a second collimating lens adjacent to the second end of the gain medium.
10. The laser of claim 1 , further comprising a plurality of reflective mirrors to form a ring laser resonator.
11. The laser of claim 1 , wherein the laser is an infrared quantum cascade laser or an infrared interband cascade laser.
12. The laser of claim 1 , wherein
a) the first acousto-optic modulator comprises a first end, a second end opposite the first end, and a first piezoelectric transducer at the first end of the first acousto-optic modulator;
b) the second acousto-optic modulator comprises a first end, a second end, and a second piezoelectric transducer at the first end of the second acousto-optic modulator;
c) a first radiofrequency generator for controlling the first piezoelectric transducer; and
d) a second radiofrequency generator for controlling the second piezoelectric transducer.
13. The laser of claim 12 , wherein
a) the first acousto-optic modulator comprises a first acoustic absorber at the second end of the first acousto-optic modulator; and
b) the second acousto-optic modulator comprises a second acoustic absorber at the second end of the second acousto-optic modulator.
14. A laser, comprising:
a) a gain medium having a first end and a second end;
b) a collimating lens adjacent to the first end of the gain medium and receiving an undiffracted output beam from the gain medium, the undiffracted beam defining a first path;
c) an anti-reflection coating at the first end of the gain medium;
d) an acousto-optic modulator configured to tune a laser wavelength across an entire gain curve, the acousto-optic modulator adjacent to the first collimating lens and opposite the gain medium, the acousto-optic modulator receiving the undiffracted output beam from the first collimating lens and subsequently emitting a diffracted beam along a second path;
e) a reflective mirror positioned to receive the diffracted beam and reflect the diffracted beam back along the second path to the acousto-optic modulator through the first path and back to the gain medium to amplify a wavelength tuned beam; and
f) a radiofrequency generator operatively connected to the acousto-optic modulator, the radiofrequency generator configured to generate a first radiofrequency and a second radiofrequency simultaneously, wherein the first radiofrequency and the second radiofrequency simultaneously generate a first laser wavelength, and a second laser wavelength.
15. The laser of claim 14 , further comprising a reflective coating at the second end of the gain medium.
16. The laser of claim 14 , wherein the acousto-optic modulator comprises a first end, a second end opposite the first end, a transparent material between the first end and the second end of the acousto-optic modulator, and a piezoelectric transducer at the first end of the acousto-optic modulator.
17. The laser of claim 16 , wherein the acousto-optic modulator comprises an acoustic absorber at the second end of the acousto-optic modulator.
18. The laser of claim 16 , wherein the acousto-optic modulator comprises:
a) a first facet adjacent to the first and second ends of the acousto-optic modulator, the first facet having a first anti-reflection coating at a desired optical wavelength, and
b) a second facet opposite the first facet and adjacent to the first and second ends of the acousto-optic modulator, the second facet having a second anti-reflection coating at a desired optical wavelength.
19. The laser of claim 14 , wherein the laser is an infrared quantum cascade laser or an infrared interband cascade laser.
20. The laser of claim 14 , further comprising a plurality of reflective mirrors to form a ring laser resonator.