AU643716B2 - Phase-locked, fibre bundle excited, stacked slabs, laser system - Google Patents
Phase-locked, fibre bundle excited, stacked slabs, laser systemInfo
- Publication number
- AU643716B2 AU643716B2 AU66207/90A AU6620790A AU643716B2 AU 643716 B2 AU643716 B2 AU 643716B2 AU 66207/90 A AU66207/90 A AU 66207/90A AU 6620790 A AU6620790 A AU 6620790A AU 643716 B2 AU643716 B2 AU 643716B2
- Authority
- AU
- Australia
- Prior art keywords
- slabs
- laser
- slab
- phase
- locked
- 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.)
- Ceased
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- Lasers (AREA)
- Laser Surgery Devices (AREA)
Description
Phase-Locked, Fibre Bundle Excited,
Stacked Slabs, Laser System
Field of the Invention
This invention relates to a high power, phase-locked stacked, multi-slab, fluid cooled, optically fibre bundle excited coupled, laser oscillator system consisting of slabs of the laser medium stacked on top of each and spaced from each other by an amount just sufficient to allow for their fluid cooling, said closely stacked laser slabs being optically excited via a pair of their side surfaces with optical radiation of narrow spectral bandwidth which matches the absorption bands of the laser medium, conveyed from a
remotely sited optical power supply using optical fibre bundles.
Only one pair of the smaller sides of the laser medium slabs need to be optically polished to allow for the passage of the high quality laser beam. The laser beam is directed from slab to slab using a series of angled reflectors and the laser resonator is terminated by two externally positioned laser mirrors, one of which reflects the laser beam up to 100% whilst the other is semi-transparent with a reflectivity which could be as low as a few per cent in order to maximise the output beam coupling. The invention has excitation light reflectors mounted above and below the stack of slabs so as to reflect any excitation radiation which is emitted through the top and bottom slab surfaces back into said slabs. The laser beam generated within said invention can consist of a single beam of elliptical cross-section or a phase-locked array of laser beams of circular cross-section. The invention has applications in the industrial, medical and defence fields.
Summary of the Prior Art
Prior art stacked slab lasers were flashtube/arc lamp excited with said fiashtubes and arc lamps sandwiched between said slabs in said stack and their output beams were not phase-locked.
The optical excitation of said slabs in the prior art slab stack lasers was via the largest faces of the said slabs and in the case of arc lamp and flashtube excitation, the process was highly
inefficient leading to severe thermal distortion of said slab. In the case where prior art slab lasers were laser diode excited, only single slabs were used. Prior art slab stack lasers were of the oscillator-amplifier "zig-zag" configuration in an effort to cancel the effects of thermally induced gradients utilising laser beams of circular cross-section which did not fully utilise the unique advantages of the rectangular configuration of the slab which favours the use of both eliiptical cross-section laser beams whose cross-section areas far exceeds that of a single laser beam of circular cross-section through the same slab laser medium. The said large surfaces of these prior art stacked slab lasers were optically polished to allow the "zig-zag" critical angle reflections of the said laser beam being amplified.
The present invention overcomes the serious defects of prior art stacked slab lasers in that the said slabs are side excited so that the slab surfaces act as a wave guide, confining most of the excitation radiation within said slabs, via critical angle
reflections, in particular, those between the largest, unpolished faces of said slabs. The present invention also significantly reduces the heat loading on said slabs because the most prolific
heat generating light source is remotely sited with only its said matching light output being conveyed to the said slabs. A further advantage of the present invention over the prior art stacked slab laser systems is the fact that the fluid cooling space between said stacks does not contain any heat generating fiashtubes and arc lamps, significantly reducing the separation between said slabs required to cool them for a given input energy and allowing for the effective phase-locking of their output beams when each slab emits either a single laser beam of eliiptical cross-section or a series of phase-locked beams of circular cross-section. Even a further advantage of the invention over the prior art stacked slab lasers is the fact that there are no electrical leads attached to the stack itself so there is no possibility of an electrical hazard existing at the output head of the said laser system. Background of the Invention
The generation of powerful laser light using compact
oscillator and oscillator amplifier systems requires as much optically excited laser medium in as small a volume as possible.
Slab lasers offer such a solution in that stacks of laser slabs with side excitation of said slab can be over 95% laser medium per given volume, there being need for only very narrow cooling
channels between said slabs.
With the advent of high power laser diode pumping and multiple fibre bundle coupling of the stacked slabs to the remotely sited optical power supplies, the heating of the slab stacks is minimal, which in turn implies that the thermally induced distortion of the
slabs is minimal and the beam quality far superior to prior art "zigzag" slab systems, where the zig-zaging was required because of said thermally induced distortions. Once such thermally induced distortions are minimised, direct beam paths through the said slab become effective as do their phase-locking capabilities.
This new art of stacked slab lasers allows for the generation of powerful laser beams, phase-locked together at the high power levels, to produce the largest possible laser beam energy from the smallest possible value of laser medium. Summary of the Invention
It is an object of the invention to provide a large volume of laser medium in the smallest possible volume of the invention by stacking laser slabs on top of each other so that the cooling channels between them is as small as possible and the opfcal excitation of said slabs is achieved via two, opposite unpolished side faces by coupling them to remotely sited optical power supplies via bund.es of optical fibres. The laser beam path, passing through the other pair of optically polished side surfaces, being defined by reflecting the said beam through each slab from top to bottom of the said slab stack using 45º turning mirrors which then form part of the optical resonator cavity which is terminated by a 100% laser beam reflector at one end and a partially transmitting laser beam reflector at the output end.
Another object of the invention is to trap the excitation light within said slab stack by placing a 100% reflecting mirror at the pump wavelength above and below said stack.
It is an object of the invention, to minimise the heating of the slabs from heat generated by the diode pumps, to remotely site said laser diode pumps and couple their narrow band optical outputs to the said unpolished side faces of said slabs using bundles of optical fibres.
Another object of the invention is to incur minimum thermal distortion of said slabs so that the laser beams being generated can be propagated directly through the said slabs without themselves being distorted by passing through distorted laser media as was the case with prior art systems due to the excessive thermal heating of said slabs during the excitation process.
A further object of the invention is to generate a laser beam of elliptical cross-section within the resonator of the invention thus providing a good match for the elongated, rectangular cross-section of a typical slab laser medium.
Yet a further object of the invention is to generate a series of laser beams of circular cross-section within the invention so that said beams can provide a good match for the elongated, rectangular cross-section of a typical slab laser medium.
It is also an object of the invention to provide an oscillator- amplifier configuration, whereby a laser beam of a circular cross- section emitted by the oscillator is split by a beam splitter array with the multiple beam output of said beamsplitter array being directed into the said slab stacks where it is amplified.
Another object of the invention is to provide for the phase- locking of the laser beam array output emitted by the stacked slab array, the said phase-locking resulting from the fact that the output laser beam array has a common origin in a master oscillator or by the fact that they are coupled to each other as they are
generated within the invention.
Brief Description of the Drawings
A better understanding of the invention may be obtained from the following considerations taken in conjunction with the
accompanying drawings which are not meant to limit the scope of the invention in any way.
Figure 1 shows a layout of the invention with the slabs stacked on top of each other and separated by a cooling fluid passage. The laser resonator cavity is a folded path cavity terminated by one fully reflective and one partially transmissive mirror at the laser wavelength positioned near to the respective input and output ends of the top and bottom slabs respectively. The laser resonator cavity is folded using 45° reflecting mirrors of up to 100%
reflectivity at the laser wavelength which direct the generated laser beam from slab to slab from the top to the bottom of the said stack of laser slabs.
Figure 2 shows the layout of the cross-section of the invention looking downwards from the top.
Figure 3 shows the configuration of the invention with its output consisting of a series of phase-locked laser beams of circular cross-section.
Figure 4 shows the oscillator configuration of the invention with phase-locked output beams which may be in the form of a single laser beam of elliptical cross-section or an array of laser beams of circular cross-section emitted by each slab.
Figure 5 shows the oscillator amplifier configuration of the invention with phase-locked output beams.
Detailed Description of the Drawings
In Figure 1 , numeral 1 indicates the laser slab whilst numeral 2 indicates the anti-reflection coated end faces of said slabs 1. Numeral 3 indicates the partially transmitting output mirror of elliptical cross-section whilst numeral 4 indicates the beam turning mirrors of rectangular cross-section used to direct the laser beam being generated from slab to slab with the stack of said slab Numeral 5 indicates the second resonator mirror which is 100% reacting at the laser wavelength, and is of elliptical cross- section.
In Figure 1 , numeral 6 indicates the high power, high quality laser output beam of elliptical cross-section generated by the invention. Numeral 7 indicates the fluid used to cool said slab whilst numeral 8 indicates a reflector to reflect any escaping excitation light back into said stack of slab.
In Figure 2, numeral 9 indicates a bundle of optical fibres used to convey the narrow spectral bandwidth excitation light from a remotely sited optical power supply (not shown) into said slab via the largest side face which need not be optically polished for this purpose.
ln Figure 3, numeral 10 indicates an array of phase-locked laser beams of circular cross-section being amplified in a slab of the invention.
In Figure 4, numeral 11 indicates phase-locked laser beams being amplified in the invention which now has two end mirrors indicated by numeral 12 and 13 respectively, numeral 12 being 100% reflective at the lasing wavelength whilst numeral 13 is partially transmissive to emit the phase-locked output beam indicated by numeral 14.
In Figure 5, numeral 15 indicates the input laser beam to be amplified by the invention after being split into an array of phase- locked laser beams by the adjustable beam splitter array indicated in part by numeral 16 with numeral 17 being the terminal 100% reflection mirror of the beam splitter array 16. Input beam 15 may be composed of a single laser beam of eliiptical cross-section or an array of laser beams of circular cross-section.
The array of phase-locked input beams in the invention is indicated by numeral 18. Numeral 19 indicates the amplified phase- locked output beam.
The invention has applications in the industrial, medical and defence fields demanding high laser beam powers.
When the high power laser output beam of the invention has an elliptical cross-section, it is a relatively simple process to optically convert such a beam into one of circular cross-section whenever the need arises.
It should be noted that since the thickness of the slab greatly exceeds the spacing between them used to flow the cooling fluid, it
is possible to dispense with the turning mirrors 4 and phase-lock the outputs of the individual slab sectors when either suitable resonator mirrors are placed either side of said stack of slab or when they are fed with a series of coherent laser beams each of which is amplified in its own particular slab.
Claims (6)
1. A stacked slab laser oscillator system consisting of:
(a) Slabs of a laser medium stacked on top of each other, their largest, unpolished faces being positioned as close as possible to each other with sufficient space between each of the said slabs to allow for effective coolant flow across said large surfaces.
(b) Two side faces of said slabs, being on opposite ends of each of the said slab, being optically polished to allow undistorted passage of laser beam being generated through said slabs, said optically polished side faces of said slabs being positioned in the same manner for each slab in said stack.
(c) A laser resonator defined by a 100% reflecting mirror, a
partially transmitting mirror and a series of 100% mirrors orientated at 45° with respect to the plane through said slabs perpendicular to their optically polished side faces such that a laser beam is generated as it is reflected through said slabs in a continuous path between said 100% mirror and said partial transmitting output mirror.
(d) The optical excitation means whereby the excitation light enters each of said slabs via the remaining pair of side faces after being generated at a remote site and conveyed via bundles of optical fibres to said faces.
2. A system as claimed in Claim 1 where the generated laser beam is of elliptical cross-section providing a good match for the elongated rectangular cross-section of said slabs.
3. A system as claimed in Claim 1 where the generated laser beam is composed of a series of laser beams of circular cross- section, said series of beams providing a good match for the elongated rectangular cross-section of said slabs.
4. A system as claimed in Claim 3 where the laser beams are phase-locked.
5. A system with a stack of slabs as claimed in Claim 1 but with the mirrors replaced by one 100% mirror and one partially
transmitting output mirror, the phase-locked output beams from all slabs combining to form a single output beam.
6. A stacked slab array as claimed in Claim 1 acting as a laser amplifier, amplifying the output beam of a single laser oscillator after it has been split by a beam splitter array, such that each of the said split beam portions passes through a particular slab in said stacked slab amplifier, the output beam array being phase- locked.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU66207/90A AU643716B2 (en) | 1989-10-25 | 1990-10-25 | Phase-locked, fibre bundle excited, stacked slabs, laser system |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AUPJ703389 | 1989-10-25 | ||
AUPJ7033 | 1989-10-25 | ||
AU66207/90A AU643716B2 (en) | 1989-10-25 | 1990-10-25 | Phase-locked, fibre bundle excited, stacked slabs, laser system |
Publications (2)
Publication Number | Publication Date |
---|---|
AU6620790A AU6620790A (en) | 1991-05-31 |
AU643716B2 true AU643716B2 (en) | 1993-11-25 |
Family
ID=25635060
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
AU66207/90A Ceased AU643716B2 (en) | 1989-10-25 | 1990-10-25 | Phase-locked, fibre bundle excited, stacked slabs, laser system |
Country Status (1)
Country | Link |
---|---|
AU (1) | AU643716B2 (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4713822A (en) * | 1985-05-24 | 1987-12-15 | Amada Engineering & Service Co., Inc. | Laser device |
US4757268A (en) * | 1985-05-22 | 1988-07-12 | Hughes Aircraft Company | Energy scalable laser amplifier |
AU583029B2 (en) * | 1984-02-15 | 1989-04-20 | Laser Holdings Limited | Composite laser oscillator |
-
1990
- 1990-10-25 AU AU66207/90A patent/AU643716B2/en not_active Ceased
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AU583029B2 (en) * | 1984-02-15 | 1989-04-20 | Laser Holdings Limited | Composite laser oscillator |
US4757268A (en) * | 1985-05-22 | 1988-07-12 | Hughes Aircraft Company | Energy scalable laser amplifier |
US4713822A (en) * | 1985-05-24 | 1987-12-15 | Amada Engineering & Service Co., Inc. | Laser device |
Also Published As
Publication number | Publication date |
---|---|
AU6620790A (en) | 1991-05-31 |
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