Claims
- 1. A method of controllably modulating the transmission of a randomly polarized laser beam comprising the steps of:
(a) providing a first acousto-optic modulator having a first Raman Nath or near Raman Nath interaction length for a laser beam at a first linear polarization; (b) providing a second acousto-optic modulator having a second Raman Nath or near Raman Nath interaction length for a laser beam at a second linear polarization different from said first linear polarization; and (c) cascading said second acousto-optic modulator with said first acousto-optic modulator in a beam path of said randomly polarized laser beam, such that the modulations thereby of said randomly polarized laser beam do not interfere with one another and sum incoherently, and the distance said randomly polarized laser beam travels through said first and second acousto-optic modulators is effectively confined to the sum of the respective interaction lengths thereof.
- 2. A method according to claim 1, wherein said first and second acousto-optic modulators are configured of respectively separate acousto-optic elements.
- 3. A method according to claim 1, wherein said first and second acousto-optic modulators are integrated in a common acousto-optic substrate.
- 4. A method according to claim 1, wherein said randomly polarized laser beam is a multi-mode laser beam.
- 5. A method according to claim 1, wherein said randomly polarized laser beam has a divergence angle of at least four milliradians.
- 6. A method according to claim 1, wherein said randomly polarized laser beam has a divergence angle of at least five milliradians.
- 7. A method according to claim 1, wherein step (c) comprises coupling said first and second acousto-optic modulators with a cooling channel structure through which a fluid cooling said first and second acousto-optic modulators passes.
- 8. A method according to claim 1, wherein step (c) comprises coupling said first and second acousto-optic modulators with a heat sink support structure that is effectively mechanically floating with respect to a housing for said first and second acousto-optic modulators.
- 9. A method according to claim 1, wherein step (c) comprises cascading said first and second acousto-optic modulators within a laser oscillation cavity of a laser generating said laser beam.
- 10. A method according to claim 1, wherein step (c) comprises cascading said first and second acousto-optic modulators external of a laser oscillation cavity of a laser generating said laser beam.
- 11. A method according to claim 1, wherein said first and second acousto-optic modulators comprise longitudinal mode acousto-optic modulators.
- 12. A method according to claim 1, wherein said first and second acousto-optic modulators comprise shear mode acousto-optic modulators.
- 13. A method according to claim 1, wherein said second linear polarization is orthogonal to said first linear polarization.
- 14. A method according to claim 1, wherein transducer input drives for said first and second acousto-optic modulators are coupled to respective first and second RF signal feed ports.
- 15. A method according to claim 1, wherein transducer input drives for said first and second acousto-optic modulators are coupled in series to an RF signal feed port.
- 16. An arrangement for controllably modulating a randomly polarized laser beam comprising:
a first acousto-optic modulator having a first Raman Nath or near Raman Nath interaction length for a laser beam having a first linear polarization; and a second acousto-optic modulator having a second Raman Nath or near Raman Nath interaction length for a laser beam having a second linear polarization different from said first linear polarization; and wherein said first and second acousto-optic modulators are disposed in cascade along a beam path of said randomly polarized laser beam, such that the modulations thereby of said randomly polarized laser beam do not interfere with one another and sum incoherently, and the distance said randomly polarized laser beam travels through said first and second acousto-optic modulators is effectively confined to the sum of the respective interaction lengths thereof.
- 17. An arrangement according to claim 16, wherein said first and second acousto-optic modulators are configured of respectively separate acousto-optic elements.
- 18. An arrangement according to claim 16, wherein said first and second acousto-optic modulators are integrated in a common acousto-optic substrate.
- 19. An arrangement according to claim 16, further including a cooling channel structure coupled to said first and second acousto-optic modulators and through which a fluid cooling said first and second acousto-optic modulators passes.
- 20. An arrangement according to claim 16, further including a heat sink support structure that is effectively mechanically floating with respect to a housing for said first and second acousto-optic modulators.
- 21. An arrangement according to claim 16, wherein said first and second acousto-optic modulators are cascaded within a laser oscillation cavity of a laser generating said laser beam.
- 22. An arrangement according to claim 16, wherein said first and second acousto-optic modulators are cascaded external of a laser oscillation cavity of a laser generating said laser beam.
- 23. An arrangement according to claim 16, wherein said first and second acousto-optic modulators comprise longitudinal mode acousto-optic modulators.
- 24. An arrangement according to claim 16, wherein said first and second acousto-optic modulators comprise shear mode acousto-optic modulators.
- 25. An arrangement according to claim 16, wherein said second linear polarization is orthogonal to said first linear polarization.
- 26. An arrangement according to claim 16, wherein transducer input drives for said first and second acousto-optic modulators are coupled to respective first and second RF signal feed ports.
- 27. An arrangement according to claim 16, wherein transducer input drives for said first and second acousto-optic modulators are coupled in series to an RF signal feed port.
- 28. An arrangement for controllably modulating a randomly polarized laser beam comprising:
a first acousto-optic modulator configured for a first linear polarization and having a first relatively short, Raman Nath or near Raman Nath interaction length for said first linear polarization that achieves a loss modulation efficiency sufficiently high to prevent the laser cavity from lasing under high gain and intense pumping conditions, when an incident laser beam has an acceptance angle that is not aligned with the Bragg angle; and a second acousto-optic modulator configured for a second linear polarization orthogonal to said first linear polarization, and having a second Raman Nath or near Raman Nath interaction length for said second linear polarization that achieves a loss modulation efficiency sufficiently high to prevent the laser cavity from lasing under high gain and intense pumping conditions, when an incident laser beam has an acceptance angle that is not aligned with the Bragg angle; and wherein
said first and second acousto-optic modulators are disposed in cascade along a beam path of said randomly polarized laser beam, such that modulations thereby of said randomly polarized laser beam do not interfere with one another and sum incoherently, and the distance said randomly polarized laser beam travels through said first and second acousto-optic modulators is effectively confined to the sum of the respective interaction lengths thereof.
- 29. An arrangement according to claim 28, wherein said first and second acousto-optic modulators comprise longitudinal mode acousto-optic modulators.
- 30. An arrangement according to claim 28, wherein said first and second acousto-optic modulators comprise shear mode acousto-optic modulators.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of co-pending U.S. Provisional Patent Application Serial No. 60/105,156, filed Oct. 21, 1998, entitled: “High Loss Modulation Acousto-Optic Q-Switch for High Power Multimode Laser,” by Eddie H. Young et al, assigned to the assignee of the present application and the disclosure of which is incorporated herein.