TEMPERATURE COMPENSATION FOR ACOUSTO-OPTC DEVICES

• US 20040105485A1
• Filed: 07/25/2003
• Published: 06/03/2004
• Est. Priority Date: 07/29/2002
• Status: Abandoned Application

• Current Assignee: Unaxis USA Incorporated (Unaxis)
• Original Assignee: Unaxis USA Incorporated (Unaxis)
• Inventors: Bures, Kenneth J, Gunes, Dogan
• Application Number:
  US10/604,503
• Publication Number:
  US 20040105485A1
• Time in Patent Office: Days
• US Class Current: 374/142
• CPC Class Codes: G01K 7/32 using change of resonant frequency of a crystal

Abstract

Methods and apparatus for compensating for temperature variations in acousto-optic devices are described. An acousto-optic tunable device according to the invention features an acousto-optic substrate having an acoustic wave transducer positioned on the acousto-optic substrate. A temperature sensor is positioned in thermal communication with the acousto-optic substrate. The temperature sensor generates an electrical signal that is related to a temperature of the acousto-optic substrate. A processor generates a control signal in response to the electrical signal generated by the temperature sensor. An oscillator receives the control signal and a frequency of the oscillator is changed in response to the control signal in order to maintain phase-matching criteria of the acousto-optic tunable device as the temperature of the acousto-optic substrate changes.

Claims

1. A method of maintaining phase-matching criteria of an acousto-optic device during temperature variations, the method comprising:

a) measuring a temperature of the acousto-optic device;

b) generating a control signal in response to the measured temperature; and

c) changing a frequency of a signal applied to an acoustic wave transducer positioned in the acousto-optic device in response to the control signal, the frequency of the signal being chosen to maintain the phase-matching criteria of the acousto-optic device.

2. The method of claim 1 wherein the measuring the temperature of the acousto-optic device comprises directly measuring a temperature of the acousto-optic device.

3. The method of claim 1 wherein the measuring the temperature of the acousto-optic device comprises directly measuring a temperature of an acousto-optic substrate in the acousto-optic device.

4. The method of claim 1 wherein the measuring the temperature of the acousto-optic device comprises indirectly measuring a temperature of the acousto-optic device.

5. The method of claim 4 wherein the indirectly measuring the temperature of the acousto-optic filer comprises measuring a delay time of an acoustic wave propagating between a first transducer and a second transducer in the acousto-optic device.

6. The method of claim 1 wherein the measuring the temperature of the acousto-optic device comprises measuring a temperature at a plurality of locations in the acousto-optic device to determine an average temperature.

7. The method of claim 1 wherein the control signal is a function of the measured temperature of the acousto-optic device and a wavelength that corresponds to the phase-matching criteria of the acousto-optic device.

8. The method of claim 1 wherein the signal applied to the acoustic wave transducer maintains the phase-matching criteria when a birefringence in at least one optical waveguide in the acousto-optic tunable device changes.

9. The method of claim 1 wherein the signal applied to the acoustic wave transducer maintains the phase-matching criteria when a speed of sound in at least one optical waveguide in the acousto-optic tunable device changes.

10. An acousto-optic tunable device comprising:

a) an acousto-optic substrate;

b) an acoustic wave transducer positioned on the acousto-optic substrate;

c) a temperature sensor that is positioned in thermal communication with the acousto-optic substrate, the temperature sensor generating an electrical signal at an output that is related to a temperature of the acousto-optic substrate;

d) a processor having an input that is electrically coupled to the output of the temperature sensor, the processor generating a control signal at an output in response to the electrical signal generated by the temperature sensor; and

e) an oscillator having a control input that is electrically coupled to the output of the processor and having an output that is electrically coupled to the acoustic wave transducer, a frequency of the oscillator being changed in response to the control signal in order to maintain phase-matching criteria of the acousto-optic tunable device as the temperature of the acousto-optic substrate changes.

11. The acousto-optic tunable device of claim 10 wherein the acousto-optic tunable device comprises an acousto-optic tunable filter.

12. The acousto-optic tunable device of claim 10 wherein the temperature sensor is positioned proximate to the acousto-optic substrate.

13. The acousto-optic tunable device of claim 10 wherein the temperature sensor is embedded in the acousto-optic substrate.

14. The acousto-optic tunable device of claim 10 wherein the temperature sensor is chosen from the group comprising a thermocouple, a thermistor, and a semiconductor junction.

15. The acousto-optic tunable device of claim 10 wherein the temperature sensor measures an average temperature of a portion of the acousto-optic substrate.

16. The acousto-optic tunable device of claim 10 wherein the oscillator comprises a voltage controlled crystal oscillator (VXCO).

17. The acousto-optic tunable device of claim 10 wherein the oscillator comprises a digital frequency synthesizer.

18. The acousto-optic tunable device of claim 10 wherein the control signal is a function of the temperature of the acousto-optic substrate and a desired phase matching wavelength of the acousto-optic tunable device.

19. The acousto-optic tunable device of claim 10 wherein the frequency of the oscillator is changed in order to maintain the phase-matching criteria when a birefringence in at least one optical waveguide in the acousto-optic tunable device changes.

20. The acousto-optic tunable device of claim 10 wherein the frequency of the oscillator is changed in order to maintain the phase-matching criteria when a speed of sound in at least one optical waveguide in the acousto-optic tunable device changes.

21. A device for maintaining phase-matching criteria in an acousto-optic device during temperature variations, the device comprising:

a) means for measuring a temperature of the acousto-optic device;

b) means for generating a control signal in response to the measured temperature; and

c) means for changing the frequency of a signal applied to an acoustic wave transducer positioned in the acousto-optic device in response to the control signal, the frequency of the signal being chosen to maintain the phase-matching criteria of the acousto-optic device.