WO1991005383A1 - Diode assisted, optical pump switched solid state laser - Google Patents
Diode assisted, optical pump switched solid state laser Download PDFInfo
- Publication number
- WO1991005383A1 WO1991005383A1 PCT/AU1990/000459 AU9000459W WO9105383A1 WO 1991005383 A1 WO1991005383 A1 WO 1991005383A1 AU 9000459 W AU9000459 W AU 9000459W WO 9105383 A1 WO9105383 A1 WO 9105383A1
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- WO
- WIPO (PCT)
- Prior art keywords
- laser
- output
- rod
- medium
- light
- 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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
-
- 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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/0915—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light
- H01S3/092—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light of flash lamp
- H01S3/093—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light of flash lamp focusing or directing the excitation energy into the active medium
-
- 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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/02—Constructional details
- H01S3/04—Arrangements for thermal management
- H01S3/0407—Liquid cooling, e.g. by water
-
- 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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094049—Guiding of the pump light
- H01S3/094053—Fibre coupled pump, e.g. delivering pump light using a fibre or a fibre bundle
Definitions
- This invention relates to the high repetition rate switching of a solid state laser using low cost diode equivalent fiber coupled optical filtered outputs of gaseous discharge lamps to raise said solid state laser to its operating threshold and pulse pumping safd solid state laser above its operating threshold via the optical outputs of arrays of fiber coupled high cost diode arrays which allow for pulsed outputs from said solid state laser at the pulsed repetition rate of the said diode arrays, said invention consisting of a laser rod medium, fluid cooled and surrounded by an array of optical fiber ends, some of which convey the optically filtered outputs of discharge lamps and others the optical output of laser diode arrays for the excitation of both rod and slab lasers.
- the invention has applications in the industrial, medical, scientific and defence fields.
- the present invention overcomes the defects of prior art systems because it simultaneously uses both the diode equivalent output of gaseous discharge lamps and the rapidly pulsed output of laser diode arrays to uniformly excite a solid state laser medium, such that the optical output of the gaseous discharge lamps bring the said solid state laser medium up to its lasing threshold within a particular laser configuration and the rapidly pulsed optical output of the diode array excites said laser medium well above the operating threshold in such a manner that the resulting laser beam generated in the said laser medium is switched at the same repetition rate as the said diode pump pulse.
- the invention provides for the necessary uniformity of the pump light, high pumping efficiency within the said laser medium, minimum thermal stresses in said medium, and the control necessary to modulate the output of the said laser medium to duplicate both the profile and the repetition rate of the diode pump pulse.
- Maiman's first laser was the ultimate in simplicity consisting of a single rod of lasing material whose ends were optically polished one having, ideally, a 100% reflector at the laser wavelength whilst the other end, the output end, was coated with a partially transmitting mirror through which the output laser beam emerged.
- This first laser all one had to do was excite it with a pulse of white light to ensure that the absorption bands of the rod laser medium was well provided for. 5
- efforts to improve Maiman's first laser have resulted in ever more complex systems. In this invention we have dispensed with all of this complexity and returned to the simplicity of the first rod laser providing means to both operate at high continuous wave output powers and also high ⁇ o pulse repetition rates without the need for complex mechanical or electro-optic switches.
- This new laser or more precisely, the fully optimsed old laser of thirty years ago, utilises two types of matched excitation light sources.
- the light output of gaseous discharge lamps is 5 optically filtered (as described in a co-pending patent application) and optical fibre bundle coupled so that the output light is distributed in the form of the light profile absorbed by the laser medium being excited.
- This mode of optically exciting the laser medium provides threshold power at relatively low wall plug efficiency bearing in mind that gaseous discharge lamps are 5 invariably white light sources.
- the overall operating efficiency of the invention is increased substantially by operating above its lasing threshold using the excitation light emitted by laser diode arrays tuned to match the absorption bands of the lasing medium and fibre bundle coupled as in the case with the optically filtered output of the gaseous discharge lamps the light output of the laser diode arrays is uniformly distributed along the body of the laser medium, thus ensuring the highest possible excitation uniformity.
- the cylindrical arrangement of the fibre output ends around the rod laser medium ensuring that the excitation process can achieve a Gaussian intensity distribution of the output beam or a flat intensity distribution as the need may be.
- the invention To modulate the output of the invention, it is first of all excited to its lasing threshold, or more exactly just below its lasing threshold, with the filtered light output of the gas lamps then brought above its lasing threshold with the pulsed output of the laser diode arrays.
- the laser beam output then follows the profile of the pulsed diode array output.
- the invention can either be modulated or effectively single pulse switched the process depending only on the rate at which the laser diode array can be modulated or switched.
- the invention for the first time in the 30 year history of lasers, provides for full optimisation of Maiman's original rod laser whilst maintaining its extreme simplicity.
- Another object of the invention is to provide multiple absorption band optical pumping of the rod laser medium to its operating threshold via fibre bundle coupled, optically filtered output of gaseous discharge lamps.
- Another object of the invention is to single pulse switch the laser output beam in the same pulse format as the diode array can be single pulse switched.
- Figure 1 is a schematic layout of the laser mode medium uniformly coupled to both an array of gas discFfarge tubes and an array of laser diodes.
- Figure 2 we show another cross-section of the invention with the mirrored rod laser medium forming a laser oscillator, excited to its operating threshold via the diode equivalent optical output of gas discharge lamps and well above the operating 5 threshold via the pulsed optical outputs of laser diode arrays. It should be noted that the invention also allows for continuous wave outputs from such a solid state laser media.
- numeral 1 indicates an array of gas discharge ⁇ o lamps.
- Numeral 2 indicates the optical filters used to filter out all wavelengths of lamp array 1 which do not match the absorption bands of the laser medium as is the one with laser diode pumps.
- Numeral 3 indicates the optical fibers whose cores are of much greater diameter than the thickness of their cladding, allowing for
- Numeral 6 indicates a stack of pulsed laser diodes which emits these narrow bandwidth pump light indicated by numeral 7, directly into the
- the invention provides a cost effective avenue for the production of high quality, pulsed laser beam output from solid ⁇ o state lasers in a manner not previously possible, when completely random oscillators of such optically excited laser resonators was the order of the day.
- the invention has applications in the industrial, medical, defence and optical communication fields. It should be noted that 5 the diode array output pulse can be emitted in a travelling wave formation to excite the said laser medium 4.
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Lasers (AREA)
Abstract
This invention relates to a solid state laser system where the optical output of an array of gas discharge lamps (1) are optically filtered (2) and the resultant optical output fibre bundle (3) coupled into a laser rod medium (4) which is fluid cooled (5). Above its lasing threshold, laser rod (4) is excited by the output of the laser diode array (6) via optical fibre bundle (7). In this manner, the optically filtered output of the gas discharge lamps (1) is used to bring the laser rod (4) up to lasing threshold at relatively low overall efficiency whilst above threshold excitation is achieved with the light output of laser diode array (6) which can either be modulated or single pulse switched.
Description
Diode Assisted, Optical Pump Switched Solid State Laser
Field of the Invention
This invention relates to the high repetition rate switching of a solid state laser using low cost diode equivalent fiber coupled optical filtered outputs of gaseous discharge lamps to raise said solid state laser to its operating threshold and pulse pumping safd solid state laser above its operating threshold via the optical outputs of arrays of fiber coupled high cost diode arrays which allow for pulsed outputs from said solid state laser at the pulsed repetition rate of the said diode arrays, said invention consisting of a laser rod medium, fluid cooled and surrounded by an array of optical fiber ends, some of which convey the optically filtered outputs of discharge lamps and others the optical output of laser diode arrays for the excitation of both rod and slab lasers. The invention has applications in the industrial, medical, scientific and defence fields.
Summary of the Prior Art
The present invention overcomes the defects of prior art systems because it simultaneously uses both the diode equivalent output of gaseous discharge lamps and the rapidly pulsed output of laser diode arrays to uniformly excite a solid state laser medium, such that the optical output of the gaseous discharge lamps bring the said solid state laser medium up to its lasing threshold within a particular laser configuration and the rapidly pulsed optical output of the diode array excites said laser medium well above the operating threshold in such a manner that the resulting laser beam
generated in the said laser medium is switched at the same repetition rate as the said diode pump pulse. The invention provides for the necessary uniformity of the pump light, high pumping efficiency within the said laser medium, minimum thermal stresses in said medium, and the control necessary to modulate the output of the said laser medium to duplicate both the profile and the repetition rate of the diode pump pulse.
Optical excitation switching of solid state lasers could not be achieved until the advent of diode array pumping. On the other hand, the very high cost of said diode arrays prohibit the commercialisation of this new optical excitation switching of solid state lasers unless the diode equivalent output of gas discharge lamps are uniformity coupled to the laser medium as in the present invention. Prior art solid state lasers or prior art teachings for the excitation of solid state lasers could not achieve the single mode, optically switched output beams of the present invention, in fact, the invention allows the full optimisation of Maiman's original laser, in a manner not possible in the prior art, providing for both diffraction limited .continuous wave and pulsed outputs.
Background of the Invention
With the advent of the laser in 1960 a source of light of an entirely new type became available for the first time. Maiman's first laser was the ultimate in simplicity consisting of a single rod of lasing material whose ends were optically polished one having, ideally, a 100% reflector at the laser wavelength whilst the other end, the output end, was coated with a partially transmitting
mirror through which the output laser beam emerged. To operate this first laser, all one had to do was excite it with a pulse of white light to ensure that the absorption bands of the rod laser medium was well provided for. 5 Over the past thirty years, efforts to improve Maiman's first laser have resulted in ever more complex systems. In this invention we have dispensed with all of this complexity and returned to the simplicity of the first rod laser providing means to both operate at high continuous wave output powers and also high ι o pulse repetition rates without the need for complex mechanical or electro-optic switches.
This new laser, or more precisely, the fully optimsed old laser of thirty years ago, utilises two types of matched excitation light sources. Firstly, the light output of gaseous discharge lamps is 5 optically filtered (as described in a co-pending patent application) and optical fibre bundle coupled so that the output light is distributed in the form of the light profile absorbed by the laser medium being excited. In this way, only light that can be absorbed by the laser medium which can be effective in the actual lasing 0 process is allowed into the body of said medium thus minimising any spurious heating of said medium and maximising the efficiency of the actual lasing process. This mode of optically exciting the laser medium provides threshold power at relatively low wall plug efficiency bearing in mind that gaseous discharge lamps are 5 invariably white light sources.
The overall operating efficiency of the invention is increased substantially by operating above its lasing threshold using the
excitation light emitted by laser diode arrays tuned to match the absorption bands of the lasing medium and fibre bundle coupled as in the case with the optically filtered output of the gaseous discharge lamps the light output of the laser diode arrays is uniformly distributed along the body of the laser medium, thus ensuring the highest possible excitation uniformity. The cylindrical arrangement of the fibre output ends around the rod laser medium ensuring that the excitation process can achieve a Gaussian intensity distribution of the output beam or a flat intensity distribution as the need may be.
To modulate the output of the invention, it is first of all excited to its lasing threshold, or more exactly just below its lasing threshold, with the filtered light output of the gas lamps then brought above its lasing threshold with the pulsed output of the laser diode arrays. The laser beam output then follows the profile of the pulsed diode array output. In this way, the invention can either be modulated or effectively single pulse switched the process depending only on the rate at which the laser diode array can be modulated or switched. In this way, the invention, for the first time in the 30 year history of lasers, provides for full optimisation of Maiman's original rod laser whilst maintaining its extreme simplicity.
Summary of the Invention
It is an object of the invention to fully optimise Maiman's original rod laser so that it retains its extreme simplicity whilst emitting powerful, continuous wave, modulated or pulsed output
beams.
Another object of the invention is to provide multiple absorption band optical pumping of the rod laser medium to its operating threshold via fibre bundle coupled, optically filtered output of gaseous discharge lamps.
It is an object of the invention to provide a single band optical pumping of the rod laser medium above operating threshold with fibre bundle coupled output of a wavelength tuned diode laser array. Another object of the invention is to provide for the output ends of the fibres forming the output face of the fibre bundle delivery system to be arranged around the rod laser medium to be excited so that the output laser beam from said medium will possess a Gaussian intensity profile.
It is ^an object of the invention to modulate the laser output beam at the same rate as the diode array pump source.
Another object of the invention is to single pulse switch the laser output beam in the same pulse format as the diode array can be single pulse switched.
Brief Description of the Drawings A better understanding of the invention may be obtained from the following considerations in conjunction with the accompanying drawings which are not meant to limit the scope of the invention in any way.
Figure 1 is a schematic layout of the laser mode medium uniformly coupled to both an array of gas discFfarge tubes and an array of laser diodes.
In Figure 2, we show another cross-section of the invention with the mirrored rod laser medium forming a laser oscillator, excited to its operating threshold via the diode equivalent optical output of gas discharge lamps and well above the operating 5 threshold via the pulsed optical outputs of laser diode arrays. It should be noted that the invention also allows for continuous wave outputs from such a solid state laser media.
Detailed Description of the Invention in Figure 1 , numeral 1 indicates an array of gas discharge ι o lamps. Numeral 2 indicates the optical filters used to filter out all wavelengths of lamp array 1 which do not match the absorption bands of the laser medium as is the one with laser diode pumps. Numeral 3 indicates the optical fibers whose cores are of much greater diameter than the thickness of their cladding, allowing for
15 maximum light collection from fiber 2, and equally effective and highly uniform excitation of the laser medium indicated by numeral 4, through the cooling fluids indicated by numeral 5. Numeral 6 indicates a stack of pulsed laser diodes which emits these narrow bandwidth pump light indicated by numeral 7, directly into the
2o array of ends of part of the fiber bundle 3. This pulse excitation light uniformly excited laser medium 4 well above operating threshold at high efficiency and high repetition rates.
In Figure 2, numeral 8 indicated the fluid cooled fiber ends surrounding fluid cooled laser medium 4. One optically polished end
25 of laser medium 4 is minimised for 100% reflectivity at the lasing wavelength, whilst the other optically polished end is partially
. 7 .
mirrored as indicated by numeral 10 at the lasing wavelength allowing the emission of the single mode laser output beam indicated by numeral 11.
The pulsed light output of the diode array symmetrically 5 illuminating said medium 4 as indicated by numeral 12 gives rise to the pulsed output indicated by numeral 13, which is a high quality clone of the diode pump pulse produced at the same repetitive rate. The invention provides a cost effective avenue for the production of high quality, pulsed laser beam output from solid ι o state lasers in a manner not previously possible, when completely random oscillators of such optically excited laser resonators was the order of the day.
The invention has applications in the industrial, medical, defence and optical communication fields. It should be noted that 5 the diode array output pulse can be emitted in a travelling wave formation to excite the said laser medium 4.
Claims
1. An optically modulated rod laser system excited to its lasing threshold via fibre bundle coupled, optically filtered output of gaseous discharge lamps and then modulated above its lasing threshold via fibre bundle coupled output of wavelength tuned laser diode arrays, said system consisting of: a) A laser rod whose ends are optically polished, one of the said ends being mirrored to reflect 100% of the laser light generated within said rod whilst the other end is mirrored to partially reflect and to partially transmit the said laser light. b) An optically filtered gaseous discharge lamp surrounded by the input ends of optical fibres which convey said optically filtered light output of said lamp to the said laser rod. c) A wavelength tuned laser diode array surrounded by the input ends of optical fibres which convey the light output of the said array to the laser rod. d) An array of the output ends of a fibre bundle coupler used to convey wavelength tuned light, placed around said rod laser medium so as to allow for the optical excitation of said medium.
2. A system as claimed in claim 1 where an array of gaseous discharge lamps are used to increase the excitation power of the laser rod.
3. A system as claimed in claim 1 where the laser diode array emits its light output in a single phase.
4. A system as claimed in claim 1 where the rod laser medium is fluid cooled by flowing said cooling fluid between the outer surface of said rod and the surface formed by the output ends of said fibre bundle coupler.
5. A system as claimed in claim 1 where the laser rod is excited in a travelling wave of laser diode output light.
6. A system as claimed in claim 1 where the laser rod medium Is replaced with an identical laser slab medium.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPJ657789 | 1989-09-27 | ||
| AUPJ6577 | 1989-09-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1991005383A1 true WO1991005383A1 (en) | 1991-04-18 |
Family
ID=3774232
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/AU1990/000459 WO1991005383A1 (en) | 1989-09-27 | 1990-09-28 | Diode assisted, optical pump switched solid state laser |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO1991005383A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1850427A1 (en) * | 2006-04-29 | 2007-10-31 | Technomedica AG | Seeding of a gas laser with incoherent light for frequency stabilisation |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2495777A (en) * | 1976-05-13 | 1978-11-09 | Leonard Hughes John | Laser excitation system |
| JPS5624989A (en) * | 1979-08-09 | 1981-03-10 | Nippon Telegr & Teleph Corp <Ntt> | Solid state laser device |
| US4383318A (en) * | 1980-12-15 | 1983-05-10 | Hughes Aircraft Company | Laser pumping system |
| US4713822A (en) * | 1985-05-24 | 1987-12-15 | Amada Engineering & Service Co., Inc. | Laser device |
-
1990
- 1990-09-28 WO PCT/AU1990/000459 patent/WO1991005383A1/en unknown
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2495777A (en) * | 1976-05-13 | 1978-11-09 | Leonard Hughes John | Laser excitation system |
| JPS5624989A (en) * | 1979-08-09 | 1981-03-10 | Nippon Telegr & Teleph Corp <Ntt> | Solid state laser device |
| US4383318A (en) * | 1980-12-15 | 1983-05-10 | Hughes Aircraft Company | Laser pumping system |
| US4713822A (en) * | 1985-05-24 | 1987-12-15 | Amada Engineering & Service Co., Inc. | Laser device |
Non-Patent Citations (1)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN, E-58, page 12; & JP,A,56 024 989 (NIPPON DENSHIN DENNA KOSHA), 3 October 1981. * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1850427A1 (en) * | 2006-04-29 | 2007-10-31 | Technomedica AG | Seeding of a gas laser with incoherent light for frequency stabilisation |
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