USH822H - Method of amplitude modulating a laser beam - Google Patents
Method of amplitude modulating a laser beam Download PDFInfo
- Publication number
- USH822H USH822H US07/344,723 US34472389A USH822H US H822 H USH822 H US H822H US 34472389 A US34472389 A US 34472389A US H822 H USH822 H US H822H
- Authority
- US
- United States
- Prior art keywords
- aotf
- laser
- laser beam
- voltage
- amplitude
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 229910052785 arsenic Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 229910052716 thallium Inorganic materials 0.000 description 2
- -1 thallium arsenic selenide Chemical class 0.000 description 2
- 239000013078 crystal Substances 0.000 description 1
- 239000002178 crystalline material Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/11—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves
Definitions
- This invention is in the field of amplitude modulators for laser beams.
- the known modulators run the gamut from variable density filters to acousto-optic (AO) and electro-optic (EO) devices.
- AO and EO devices are preferred, although both are very lossy (20%-60%).
- they each generate two output beams, such that even the beam power remaining after the internal losses is split in half.
- the present invention overcomes these disadvantages by the new of an old device to effect laser beam amplitude modulation.
- This old device is a colinear acousto-optic tunable filter.
- This invention is a method of amplitude modulating a laser beam by the new use of an old device, specifically, an acoustic-optic tunable filter (AOTF).
- This AOTF consists of an anisotropic crystalline material such as thallium arsenic selenide (TI 3 AsSe 3 , or TAS for short) with a reflective interface and a piezo-electric transducer (PZT) affixed to one end of the TAS.
- PZT piezo-electric transducer
- FIG. 1 is a schematic showing of one optical layout on which the invention may be practiced.
- FIG. 2 is another schematic showing of an optical layout on which the invention may be practiced.
- AOTF acoustic-optical tunable filter
- This AOTF includes a crystal of thallium arsenic selenide (TAS), an internal reflector, and a piezo-electric transducer (PZT) for operating the device.
- This PZT designated with reference numeral 16 in the drawing is fed an A.C. signal or voltage from a modulating frequency generator 17.
- the externally located (with respect to laser cavity) AOTF acts as an amplitude modulator whenever 17 feeds an A.C. voltage to PZT 17.
- the output of 17 will be chosen.
- 17 will provide a highly-stable frequency in order that the phase the modulation envelope of the reflected beam power from a distant object may be compared with the phase of the output of 17. If the beam is used for communication, 17 vary in frequency as required.
- FIG. 2 shows laser 20 with highly reflective mirrors 21 and 22 output mirror 23.
- Output beam 24 passes through half-wave plate 26, is reflected by mirror 27 and passes through Bragg-angle reflector 28.
- Output beam 25 reflects from 28 and combined beam 29 enters AOTF 30.
- the 26-27-28 arrangement produces two orthogonal linear polarizations in beam 29. This insures proper AOTF AM operation.
- the AOTF 30 modulates input beam 29 under the action of PZT 31 fed by generator 32, to produce output beam 33.
- the method of the invention is the new use of a well-known acoustic-optic tunable filter. Rather than use the filter for its normally intended purpose, it is used to amplitude modulate a laser beam. It is especially useful for high-powered lasers such as the CO 2 type.
- the method thus includes the steps of directing the laser beam into the AOTF, and applying an A.C. voltage to the PCT of the AOTF.
Landscapes
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
- Lasers (AREA)
Abstract
An acousto-optic tunable filter (AOTF), instead of being used for its intended use of frequency or wavelength tuning a laser from within its resonant cavity, is used outside the laser cavity to amplitude modulate the output beam of the laser. This is accomplished by directing the laser output beam into the AOTF and applying an A.C. voltage to a piezo-electric transducer which is a part of the AOTF.
Description
The invention described herein may be manufactured, used, and licensed by the U.S. Government for governmental purposes without the payment of any royalties thereon.
This invention is in the field of amplitude modulators for laser beams. The known modulators run the gamut from variable density filters to acousto-optic (AO) and electro-optic (EO) devices. At present, insofar as response time and efficiency are concerned, AO and EO devices are preferred, although both are very lossy (20%-60%). Moreover, they each generate two output beams, such that even the beam power remaining after the internal losses is split in half. The present invention overcomes these disadvantages by the new of an old device to effect laser beam amplitude modulation. This old device is a colinear acousto-optic tunable filter.
This invention is a method of amplitude modulating a laser beam by the new use of an old device, specifically, an acoustic-optic tunable filter (AOTF). This AOTF consists of an anisotropic crystalline material such as thallium arsenic selenide (TI3 AsSe3, or TAS for short) with a reflective interface and a piezo-electric transducer (PZT) affixed to one end of the TAS. A laser beam directed into the AOTF is amplitude modulated by an A.C. signal applied to the PZT.
FIG. 1 is a schematic showing of one optical layout on which the invention may be practiced.
FIG. 2 is another schematic showing of an optical layout on which the invention may be practiced.
The method of the invention may be best understood if this description is taken in conjunction with the drawings. Referring now to FIG. 1, we see laser 10 with highly-reflective mirror 11 and output mirror 12, and with output beam 13 passing through quarter-wave plate 14 into acoustic-optical tunable filter (AOTF) 15. The quarter-wave plate imparts circular polarization to the linearly polarized beam 13. This is desirable because of the manner in which the AOTF operates. The AOTF is a known device disclosed in a SPIE paper entitled "Rapid Tuning Mechanism for CO2 Lasers" by L. J. Denes, et al., at the SPIE O-E LASE '88 meeting in Los Angeles, CA in January 1988. This AOTF includes a crystal of thallium arsenic selenide (TAS), an internal reflector, and a piezo-electric transducer (PZT) for operating the device. This PZT, designated with reference numeral 16 in the drawing is fed an A.C. signal or voltage from a modulating frequency generator 17. Instead of acting as a tunable filter which it usually does, the externally located (with respect to laser cavity) AOTF acts as an amplitude modulator whenever 17 feeds an A.C. voltage to PZT 17. Depending upon the use to which the modulated laser beam is put, the output of 17 will be chosen. For example, if the beam is used for CW ranging, 17 will provide a highly-stable frequency in order that the phase the modulation envelope of the reflected beam power from a distant object may be compared with the phase of the output of 17. If the beam is used for communication, 17 vary in frequency as required.
FIG. 2 shows laser 20 with highly reflective mirrors 21 and 22 output mirror 23. Output beam 24 passes through half-wave plate 26, is reflected by mirror 27 and passes through Bragg-angle reflector 28. Output beam 25 reflects from 28 and combined beam 29 enters AOTF 30. The 26-27-28 arrangement produces two orthogonal linear polarizations in beam 29. This insures proper AOTF AM operation. The AOTF 30 modulates input beam 29 under the action of PZT 31 fed by generator 32, to produce output beam 33.
The method of the invention is the new use of a well-known acoustic-optic tunable filter. Rather than use the filter for its normally intended purpose, it is used to amplitude modulate a laser beam. It is especially useful for high-powered lasers such as the CO2 type. The method thus includes the steps of directing the laser beam into the AOTF, and applying an A.C. voltage to the PCT of the AOTF.
Claims (1)
1. A method of amplitude modulating a laser beam, including the steps of:
directing said laser beam into a colinear acousto-optic tunable filter including an anisotropic medium with a piezo-electric transducer affixed thereto; and
applying an A.C. voltage to said transducer, whereby said laser is amplitude modulated to produce a modulation envelope in accordance with said A.C. voltage.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/344,723 USH822H (en) | 1989-04-28 | 1989-04-28 | Method of amplitude modulating a laser beam |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/344,723 USH822H (en) | 1989-04-28 | 1989-04-28 | Method of amplitude modulating a laser beam |
Publications (1)
Publication Number | Publication Date |
---|---|
USH822H true USH822H (en) | 1990-09-04 |
Family
ID=23351735
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US07/344,723 Abandoned USH822H (en) | 1989-04-28 | 1989-04-28 | Method of amplitude modulating a laser beam |
Country Status (1)
Country | Link |
---|---|
US (1) | USH822H (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5200964A (en) * | 1991-03-12 | 1993-04-06 | General Instrument Corporation | Broad linewidth lasers for optical fiber communication systems |
-
1989
- 1989-04-28 US US07/344,723 patent/USH822H/en not_active Abandoned
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5200964A (en) * | 1991-03-12 | 1993-04-06 | General Instrument Corporation | Broad linewidth lasers for optical fiber communication systems |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6031852A (en) | Rapid acoustooptic tuner and phase-shifter | |
US4841528A (en) | Frequency doubled, cavity dumped feedback laser | |
EP1037338B1 (en) | Tunable high powered laser | |
US5230005A (en) | Electronic tuning of a broadband laser | |
US4441186A (en) | Electronically switchable multiwavelength laser system | |
GB1363143A (en) | Polarization independent light modulation means using birefringent crystals | |
JPH0511678B2 (en) | ||
US4788514A (en) | Optical modulation arrangement | |
US5721748A (en) | Intracavity doubled solid state Raman laser system | |
US4028636A (en) | Acousto-optical deflector tuned organic dye laser | |
EP0805532B1 (en) | Optical parametric oscillator | |
US4110788A (en) | Multiple wavelength acoustooptic deflection | |
US4484333A (en) | Coupled waveguide freespace laser | |
US5394412A (en) | Power laser with deflection | |
US5754572A (en) | Mirrorless, distributed-feedback, ultraviolet, tunable, narrow-linewidth, solid state laser | |
US4105953A (en) | Chirped acousto-optic Q switch | |
USH822H (en) | Method of amplitude modulating a laser beam | |
US6836592B2 (en) | Method and apparatus for fiber Bragg grating production | |
GB1356421A (en) | Optical resonator apparatus | |
US3996525A (en) | Acousto-optically tuned laser | |
US4393517A (en) | Pulse code modulation of laser pulse tail | |
US3902137A (en) | Electro-optic diffraction grating tuned laser | |
EP0556016B1 (en) | Wavelength variable laser device | |
JP3059936B2 (en) | Variable coherence length high brightness laser design | |
KR970072571A (en) | Wavelength-Selectable Laser Oscillators in Tunable Lasers |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: UNITED STATES OF AMERICA, THE, AS REPRESENTED BY T Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:NETTLETON, JOHN E.;BARR, DALLAS N.;REEL/FRAME:005253/0982;SIGNING DATES FROM 19890427 TO 19890428 |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |