WO1991001057A1 - Grouped, phase-locked, diode arrays - Google Patents
Grouped, phase-locked, diode arrays Download PDFInfo
- Publication number
- WO1991001057A1 WO1991001057A1 PCT/AU1990/000294 AU9000294W WO9101057A1 WO 1991001057 A1 WO1991001057 A1 WO 1991001057A1 AU 9000294 W AU9000294 W AU 9000294W WO 9101057 A1 WO9101057 A1 WO 9101057A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- arrays
- phase
- locked
- diode
- laser
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
- H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0607—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature
- H01S5/0612—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature controlled by temperature
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/06233—Controlling other output parameters than intensity or frequency
- H01S5/06243—Controlling other output parameters than intensity or frequency controlling the position or direction of the emitted beam
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
- H01S5/42—Arrays of surface emitting lasers
Definitions
- This invention relates to a phase-locked, diode array laser consisting of groups of coherently phase-locked arrays emitting diffraction limited laser beams which themselves phase-lock to produce a larger diameter laser beam, itself being diffraction limited.
- the invention has applications in industrial, medical and defence fields.
- phase-locked, diode laser arrays are well known in the art. However, they have a major defect in that they are not coherently phase-locked, large arrays tending to phase-lock in pockets, a characteristic which leads to multi-lobed outputs. Another defect of prior art diode laser arrays arises from the fact that approximately 60% of the electrical input power into the array appears as heat within the array itself. As these prior art diode arrays are scaled to higher power levels by increasing the number of diodes within the array, the effects of the thermal problems becomes more severe leading to defective phase-locking of the array as a whole.
- each of the diodes within about ten microns (10-3 cms) of each other within the array so that they can be optically coupled to each other, a process referred to as evanescent coupling of the diodes within the array.
- the present invention overcomes the defects of prior art systems by limiting the cross-sectional area of the laser diode array on a given substrate so that each such diode array emits a diffraction limited laser beam which in turn phase-locks with its neighbours to produce groups of phase-locked diffraction limited laser beams which in turn combine together to form a single phase- locked, diffraction limited laser output beam from said system.
- groups of diode arrays they have to be separated for optimum cooling, but collectively coupled for ⁇ o optimum phase-locking, two contradictory requirements which have to be balanced in this invention.
- a given array has to be of a size that provides good phase-locking resulting in a single lobed output beam and experience indicates that the optimum size for such arrays lies in the 100 - 1 ,000 diode
- a 1 ,000 diode array would have a circular cross-sectional area of about 300 microns (3 x 10-2 cms) in diameter.
- phase-locking techniques include a partially reflective output window which reflects the light output from one diode array group to the others, or a Fabry-Perot etalon window which also allows the light from various diodes to be transferred amongst each other.
- said Fabry-Perot etalon can be in the form of a micro lens array whilst the other face is mirrored to partially transmit the laser beam.
- Laser diodes provide a most effective way of converting electrical energy into laser beam energy with conversion efficiencies of over 30% being achievable.
- Laser diodes have been developed along two avenues, namely, laser diodes which emit their output beams parallel to the substrate on which the diodes have been deposited and diodes which emit their output beam perpen ⁇ dicular to their substrate.
- the emitted laser beam has a rectangular cross-section whilst in the latter case the ⁇ o emitted laser beam can be of any practical cross-sectional configuration including circular cross-section.
- Figure 1 shows a schematic layout of the diode arrays of the invention with the grouping of the diodes such as to balance their cooling and optical coupling requirements.
- Figure 2 shows the use of an output window to reflect light from one diode array group to another.
- Figure 3 shows the use of an output etalon to couple the light from one diode group to another.
- Figure 4 shows the manner in which the output of the invention 25 can be frequency shifted using non-linear optical crystals.
- numeral 1 indicates the substrate onto which the groups of diode arrays, indicated by numeral 2 are positioned.
- Numeral 3 indicates the rows of laser diodes which optically couple diode array groups 2 to enhance their mutual phase-locking.
- numeral 4 indicates an output window which reflects small amounts of laser light indicated by numeral 5 from diode array groups 2 back into said groups producing an optical coupling means for their coherent phase-locking in the format of ⁇ o multiple output beams indicated by numeral 6 into the single output beam indicated by numeral 7.
- numeral 8 indicates a Fabry-Perot etalon which has partially transmitting mirrors on its two faces, indicated by numeral 9 and 10 respectively, allowing light indicated by numeral
- numeral 12 indicates a telescope used to reduce the cross-section of output beam 7 of the invention to increase its
- Numeral 13 indicates the frequency converting crystal whilst numeral 14 indicates the frequency converted laser beam.
- the Invention has applications in the industrial, medical and defence fields particularly in areas where frequency tuneable
- the invention can be temperature tuned at the diode output wavelength by over 0.25 nanometers per degree centigrade. Normally, such diodes can operate over relatively wide
- Computer controlled switching of the diode arrays of the invention can control the phases of the emitted laser beams to ensure the precise steering of the final phase-locked output laser beam of the invention.
- the invention can operate either in a continuous wave or pulsed mode at high repetition rates.
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Semiconductor Lasers (AREA)
Abstract
The invention relates to a phase-locked diode array laser which consists of a group of phase-locked, optically coupled laser diode arrays (2), such that the arrays of phase locked output beams (6) are themselves phase locked to produce effectively a single beam output (7). Inter diode array optical coupling may be provided by extra rows of laser diodes linking the arrays or by optical fibres. Also claimed is steering of the phase-locked output by emission of light from one end of a group of diode arrays before light is emitted from the opposite end.
Description
Grouped, Phase-Locked, Diode Arrays
Field of the Invention
This invention relates to a phase-locked, diode array laser consisting of groups of coherently phase-locked arrays emitting diffraction limited laser beams which themselves phase-lock to produce a larger diameter laser beam, itself being diffraction limited. The invention has applications in industrial, medical and defence fields.
Summary of the Prior Art
Prior art, phase-locked, diode laser arrays are well known in the art. However, they have a major defect in that they are not coherently phase-locked, large arrays tending to phase-lock in pockets, a characteristic which leads to multi-lobed outputs. Another defect of prior art diode laser arrays arises from the fact that approximately 60% of the electrical input power into the array appears as heat within the array itself. As these prior art diode arrays are scaled to higher power levels by increasing the number of diodes within the array, the effects of the thermal problems becomes more severe leading to defective phase-locking of the array as a whole. To ensure the coherent phase-locking of a prior art diode array it is necessary to position each of the diodes within about ten microns (10-3 cms) of each other within the array so that they can be optically coupled to each other, a process referred to as evanescent coupling of the diodes within the array.
SUBSTITUTE SHE
The present invention overcomes the defects of prior art systems by limiting the cross-sectional area of the laser diode array on a given substrate so that each such diode array emits a diffraction limited laser beam which in turn phase-locks with its neighbours to produce groups of phase-locked diffraction limited laser beams which in turn combine together to form a single phase- locked, diffraction limited laser output beam from said system. To achieve such operation of groups of diode arrays, they have to be separated for optimum cooling, but collectively coupled for ι o optimum phase-locking, two contradictory requirements which have to be balanced in this invention. To effectively cool the arrays, a given array has to be of a size that provides good phase-locking resulting in a single lobed output beam and experience indicates that the optimum size for such arrays lies in the 100 - 1 ,000 diode
15 range depending on the type of diode lasers involved. For example, a 1 ,000 diode array would have a circular cross-sectional area of about 300 microns (3 x 10-2 cms) in diameter. By interlacing such arrays with diode bars, the whole array can then be phase-locked without introducing optical waveguide couplers, for example, single
2o mode optiqal fibre inter-connections. Alternative phase-locking techniques include a partially reflective output window which reflects the light output from one diode array group to the others, or a Fabry-Perot etalon window which also allows the light from various diodes to be transferred amongst each other. On the face of
25 tliό said Fabry-Perot etalon can be in the form of a micro lens array whilst the other face is mirrored to partially transmit the laser beam.
SUBSTITUTE SHEET
Background of the Invention
Laser diodes provide a most effective way of converting electrical energy into laser beam energy with conversion efficiencies of over 30% being achievable. Laser diodes have been developed along two avenues, namely, laser diodes which emit their output beams parallel to the substrate on which the diodes have been deposited and diodes which emit their output beam perpen¬ dicular to their substrate. In the former case, the emitted laser beam has a rectangular cross-section whilst in the latter case the ι o emitted laser beam can be of any practical cross-sectional configuration including circular cross-section.
Brief Description of the Drawings
A better understanding of the invention may be obtained from the following considerations taken in conjunction with the is drawings which are not meant to limit the scope of the invention in any way.
Figure 1 shows a schematic layout of the diode arrays of the invention with the grouping of the diodes such as to balance their cooling and optical coupling requirements. 20 Figure 2 shows the use of an output window to reflect light from one diode array group to another.
Figure 3 shows the use of an output etalon to couple the light from one diode group to another.
Figure 4 shows the manner in which the output of the invention 25 can be frequency shifted using non-linear optical crystals.
SUBSTITUTE SHEET
Detailed Description of the Invention
In Figure 1, numeral 1 indicates the substrate onto which the groups of diode arrays, indicated by numeral 2 are positioned.
Numeral 3 indicates the rows of laser diodes which optically couple diode array groups 2 to enhance their mutual phase-locking.
In Figure 2, numeral 4 indicates an output window which reflects small amounts of laser light indicated by numeral 5 from diode array groups 2 back into said groups producing an optical coupling means for their coherent phase-locking in the format of ι o multiple output beams indicated by numeral 6 into the single output beam indicated by numeral 7.
In Figure 3, numeral 8 indicates a Fabry-Perot etalon which has partially transmitting mirrors on its two faces, indicated by numeral 9 and 10 respectively, allowing light indicated by numeral
15 11 from a particular diode array to be coupled into its neighbours, a process allowing for the coherent phase-locking of all the said groups of diode arrays.
In Figure 4, numeral 12 indicates a telescope used to reduce the cross-section of output beam 7 of the invention to increase its
2o intensity to a level where its frequency conversion becomes efficient. Numeral 13 indicates the frequency converting crystal whilst numeral 14 indicates the frequency converted laser beam.
The Invention has applications in the industrial, medical and defence fields particularly in areas where frequency tuneable
25 outputs are required. The invention can be temperature tuned at the diode output wavelength by over 0.25 nanometers per degree centigrade. Normally, such diodes can operate over relatively wide
SUBSTITUTE SHEET
temperature ranges, for example -15°C to +70°C. This implies that the frequency doubled outputs can also be tuned. However, to achieve higher frequency conversion efficiency, the output beam of the invention has to be concentrated using a reversal telescope in order to achieve the required beam intensities.
Computer controlled switching of the diode arrays of the invention can control the phases of the emitted laser beams to ensure the precise steering of the final phase-locked output laser beam of the invention. The invention can operate either in a continuous wave or pulsed mode at high repetition rates.
SUBSTITUTE SHEET
Claims
1. A coherently phase-locked laser diode array consisting of a group of laser diode arrays, themselves phase-locked, and optically coupled to each other, such that the arrays of phase-locked output beams from said group of phase-locked arrays are themselves phase- locked to produce what is effectively a single beam output.
2. A system as claimed in Claim 1 where the inter array optical coupling is provided by rows of laser diodes identical to the laser diodes forming said arrays. ι o
3. A system as claimed in Claim 1 where the inter array optical coupling is provided by optical fibres.
4. A system as claimed in Claim 1 where the laser diode arrays are grouped together in groups, each sub group being phase-locked with respect to each other.
15 5. A system as claimed in Claim 1 where the laser light emitted by the laser diode arrays at the end of a given diameter of a group of said arrays is emitted before the light from the diode arrays at the opposite end of said diameter of said group of arrays, leading to the steering of said phase-locked output of said array.
2o 6. A system as claimed in Claim 1 where all of the laser diodes forming said arrays have a conversion, partially transmitting mirror.
7. A system as claimed in Claim 1 where the diode arrays are grouped in a haxagonal pattern such that each of the individual
25 arrays are equidistant from each other.
8. A system as claimed in Claim 1 where the phase-locking of the
SUBSTITUTE SHEE said diode arrays are achieved by fibre bundle coupling the rear faces of said diode arrays.
SUBSTITUTE SHEET
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPJ5123 | 1989-07-06 | ||
| AUPJ512389 | 1989-07-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1991001057A1 true WO1991001057A1 (en) | 1991-01-24 |
Family
ID=3774043
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/AU1990/000294 WO1991001057A1 (en) | 1989-07-06 | 1990-07-06 | Grouped, phase-locked, diode arrays |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO1991001057A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1992003862A1 (en) * | 1990-08-22 | 1992-03-05 | Massachusetts Institute Of Technology | Microchip laser array |
| DE4301689A1 (en) * | 1993-01-22 | 1994-07-28 | Deutsche Forsch Luft Raumfahrt | Power controlled fractal laser system |
| DE4490251B4 (en) * | 1993-01-22 | 2004-04-22 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Phase-controlled fractal laser system |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU5351479A (en) * | 1978-12-08 | 1980-06-26 | Ajoy Kumar Ghatak | Phased array optical scanning |
| US4764095A (en) * | 1985-12-04 | 1988-08-16 | Fickelscher Kurt G | Rotary slide compressor with thin-walled, deformable sleeve |
| US4813762A (en) * | 1988-02-11 | 1989-03-21 | Massachusetts Institute Of Technology | Coherent beam combining of lasers using microlenses and diffractive coupling |
| WO1989012923A1 (en) * | 1988-06-16 | 1989-12-28 | Austral Asian Lasers Pty. Ltd. | Hybrid laser |
| EP0363076A2 (en) * | 1988-10-07 | 1990-04-11 | Trw Inc. | Semiconductor laser array having high power and high beam quality |
-
1990
- 1990-07-06 WO PCT/AU1990/000294 patent/WO1991001057A1/en unknown
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU5351479A (en) * | 1978-12-08 | 1980-06-26 | Ajoy Kumar Ghatak | Phased array optical scanning |
| US4764095A (en) * | 1985-12-04 | 1988-08-16 | Fickelscher Kurt G | Rotary slide compressor with thin-walled, deformable sleeve |
| US4813762A (en) * | 1988-02-11 | 1989-03-21 | Massachusetts Institute Of Technology | Coherent beam combining of lasers using microlenses and diffractive coupling |
| WO1989012923A1 (en) * | 1988-06-16 | 1989-12-28 | Austral Asian Lasers Pty. Ltd. | Hybrid laser |
| EP0363076A2 (en) * | 1988-10-07 | 1990-04-11 | Trw Inc. | Semiconductor laser array having high power and high beam quality |
Non-Patent Citations (5)
| Title |
|---|
| APPLIED PHYSICS LETTERS, Volume 41, No. 2, 15 July 1982, SCIFRES et al., "High Power Coupled Multiple Stripe Qauntum Well Injection Lasers", see pages 118 to 120. * |
| APPLIED PHYSICS LETTERS, Volume 43, No. 6, 15 September 1983, KATZ et al., "Phase-Locked Semiconductor Laser Array with Separate Contacts", see pages 521 to 523. * |
| APPLIED PHYSICS LETTERS, Volume 48, No. 26, 30 June 1986, WANG et al., "In-Phase Locking in Diffraction Coupled Phased-Array Diode Lasers", see pages 1770 to 1772. * |
| APPLIED PHYSICS LETTERS, Volume 49, No. 24, 15 December 1986, WELCH et al., "High-Power (cw) in-Phase Locked 'y' Coupled Laser Arrays", see pages 1632 to 1634. * |
| APPLIED PHYSICS LETTERS, Volume 52, No. 21, 23 May 1988, LEGER et al., "Coherent Addition of AlgaAs Lasers Using Microlenses and Diffractive Coupling"; & US,A,4 813 762 (LEGER et al.), 21 March 1989, see pages 1771 to 1773. * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1992003862A1 (en) * | 1990-08-22 | 1992-03-05 | Massachusetts Institute Of Technology | Microchip laser array |
| DE4301689A1 (en) * | 1993-01-22 | 1994-07-28 | Deutsche Forsch Luft Raumfahrt | Power controlled fractal laser system |
| DE4490251B4 (en) * | 1993-01-22 | 2004-04-22 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Phase-controlled fractal laser system |
| DE4490252B4 (en) * | 1993-01-22 | 2005-07-28 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Power driven fractal laser system - controls individual semiconductor units to illuminate different target surface elements with different intensities |
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