CN105305207A - End-pumped single-pass traveling wave laser amplifier - Google Patents
End-pumped single-pass traveling wave laser amplifier Download PDFInfo
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- CN105305207A CN105305207A CN201410682288.5A CN201410682288A CN105305207A CN 105305207 A CN105305207 A CN 105305207A CN 201410682288 A CN201410682288 A CN 201410682288A CN 105305207 A CN105305207 A CN 105305207A
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Abstract
The invention discloses an end-pumped single-pass traveling wave laser amplifier, which comprises a semiconductor laser. The semiconductor laser is used for providing pumped laser, the right side of the semiconductor laser is provided with a pumped light coupling and focusing system, the upper end and the right end of the pumped light coupling and focusing system are respectively provided with an incident laser coupling and focusing system and a laser crystal which is doped and bonded in a stepped mode; and matched crystal heat sinks are arranged around the laser crystal. The end-pumped single-pass traveling wave laser amplifier has the beneficial effects that according to the laser crystal, through reasonably designing the doping concentration and the length of each section of the crystal, thermal load of the pumped light is uniformly shouldered by each section of the crystal; at the same pumped power, thermal distribution inside the laser crystal is more uniform, the highest temperature rise is lower, the thermal stress and the thermal lens effects are smaller, higher pumped power can be borne, and degradation on beam quality of the amplified laser is smaller; and the output laser power is higher, the beam quality is better, the structure is simple, and the operation is stable and reliable.
Description
Technical field
The present invention relates to technical field of solid laser, specifically, relate to a kind of end pumping one way row ripple laser amplifier.
Background technology
The solid state laser of laser diode (LD) pumping has the advantages such as volume is little, the life-span is long, energy conversion efficiency is high, pump mode is flexible, is the main flow direction of current solid Development of Laser Technology; Along with the maturation day by day of high power laser diode technology, the power output of laser diode pump solid state laser device is also more and more higher.The pump mode of laser diode is mainly divided into end pumping and profile pump, compared to profile pump, the outstanding advantages of end pumping to make pump light and laser obtain larger mode distributions overlap, thus realize high light-phototranstormation efficiency and high laser beam quality; Shortcoming is that the gain mode volume that the pump light injected from laser crystal end face activates is relatively little, and pump power density can not be too high, otherwise easily damages gain media, so the power output of end-face pump solid laser is relatively low.
In the application of some laser, as precise laser processing, often requiring that laser had both had high beam quality is TEM one by one
00mould exports (the M2 factor is little), has very high power output to be tens watts again and even goes up hectowatt; This index is only by the more difficult realization of separate unit end pump solid state laser, because the good characteristic of laser beam will be kept as beam divergence angle, monochromaticjty etc., the bore of operation material and length all should not be too large; In addition, come and go higher by the general specific power output of the power of gain media in laser resonant cavity, the fragile operation material of too high laser power density.So, generally use " master oscillation power amplification (MOPA) system " be made up of laser generation level+power-amplifier stage to realize high power, high light beam quality Laser output.In MOPA system, the power output of laser generation level can be very low, but need provide other key technical index, as wavelength, pulsewidth, and spectrum width (live width), repetition rate, beam quality etc.; As far as possible the Main Function of power-amplifier stage is amplified to desired level to laser power keeping these key indexs while.
Because transformer equivalent on the Excited state effect in atomic energy level transition process and Energy Transfer should, pump light for laser amplifier energy is provided while also can produce " used heat ", the laser power that MOPA system finally exports is higher, pump power required for amplifying stage is higher, and this used heat is also more.The mode that end pumping generally adopts laser crystal side to cool, this makes the central temperature of laser crystal higher than lip temperature, so crystal radial direction can produce thermal gradients.In addition, for the laser crystal of Uniform Doped, pump light is exponentially decayed after entering crystal, and the central temperature right and wrong of crystal are equally distributed---and successively decrease in the axial direction in the direction of propagation along pump light, so the front end face central temperature of pump light incidence is the highest, radial thermal gradient is also maximum.Along with the increase of injecting pump power, this thermal gradient can be increasing, and excessive thermal gradient mainly can bring two serious problems:
1. deteriorated beam quality, due to thermo-optic effect, the refractive index of laser crystal is with temperature change, and this causes the amplified laser beam light path that its center and peripheral experiences after laser crystal different, namely creates thermal lens effect.In addition, the end-face deformation that crystal front end face produces at too high a temperature also has contribution to thermal lensing effect, research shows, even can account for half (see X.Peng, A. for this contribution of some laser crystal, etal., " StudyofthemechanicalpropertiesofNd:YVO4crystalbyuseoflas erinterferometryandfiniteelementanalysis, " Appl.Opt., vol.40,1396, (2001)).Thermal lensing effect makes incident laser can be focused on consumingly after amplifying stage, and pump power density is higher, and focussing force is more obvious, and this can bring difficulty to the light path design between amplifying stage, also can reduce the spatial stability of outgoing laser beam.Moreover, this thermal lens in laser crystal is not perfect lens, only in a bit of region of both sides, center, pumped region, crystal refractive index distribution meets the parabolic type distribution of desirable thermal lens, refraction index profile outside central area can depart from parabolic type distribution, and the result that it brings is exactly that edge, pumped region can produce the higher order aberratons effects such as spherical aberration.And pump power density is higher, the temperature of germ nucleus is higher, and the region producing spherical aberration is also larger, and this can cause the laser beam be exaggerated to produce distortion, and beam quality is by serious deterioration.
2. damage laser crystal, especially to Nd:YVO
4the laser crystal that this kind of thermal conductivity is lower.Thermal gradient in laser crystal can produce thermal stress, and germ nucleus temperature is high, produces compression; Crystal on side face temperature is low, produces tangential and axial tension stress.And general crystal anti-pressure ability is far above resistance to tension, so the lens lesion majority that too high pump light causes occurs in the lateral edges near pumping incidence surface.The induced damage limit of crystal finally determines the injected pump power of laser crystal, also determines the amplifying power of laser power amplifier.
In order to solve above-mentioned two problems, this area generally uses two kinds of solutions: a kind of is use longer wavelength pumping, reduces quantum defect effect, fundamentally reduces the ratio of heating in laser energy conversion, with Nd:YVO
4crystal is example, and the laser diodes such as 880nm, 888nm and 914nm can be used as pumping source; Another kind reduces the heat load of pump light on laser crystal incident end face, thus reduce the maximum temperature of bearing germ nucleus and maximum thermal gradient.A kind of conventional method uses both-end pumping structure; 2006, LouisMcDonagh proposes to use 888nm coaxially to feed back pump technology, the remaining pump light of first pass crystal is returned along original route again absorbed by laser crystal, its essence is also that both-end pumping structure is (see LouisMcDonaghandRichardWallenstein, High-efficiency60WTEM00Nd:YVO4oscillatorpumpedat888nm, vol.31,3297, (2006)).Bear to two end faces although this method shares the heat load that pumping brings, crystal axis Temperature Distribution is upwards still very uneven---successively decrease from two end faces to center.A kind of method is also had to be that multiple laser crystal is shared in pumping heat load, thus composition multi-stage power amplifier.Although this structure finally can obtain the power output of hundreds of watts, but its bulky, complex structure, and because the thermal focal length of laser crystal changes with pump power, often need special light path design to realize the pattern matching of every one-level pump light and laser between each amplifying stage, this can increase design and debug difficulties.In addition, in recent years a kind of emerging method is the composite crystal of use one section of non-doped crystal and one section of Uniform Doped crystal bonding, the heat load of pump light at doped region incident end face can be shared in non-doped region, thus reduces maximum temperature and the end-face deformation of germ nucleus.It is even that the weak point of this method is still crystal axis temperature distributing disproportionation upwards, only has the interface place thermal gradient of non-doped region and doped region maximum.
For the problem in correlation technique, at present effective solution is not yet proposed.
Summary of the invention
The object of this invention is to provide a kind of end pumping one way row ripple laser amplifier, higher end pumping power and unlikely damage laser crystal can have been born on the one hand; On the other hand, this device under same pump power thermal lensing effect and thermic aberration effect less, the power amplifier before being conducive to avoiding is to the deterioration of incident laser beam quality; In addition, this apparatus structure is simple, volume ratio both-end pumping structure and multistage structure for amplifying less, can effectively overcome currently available technology above shortcomings.
The object of the invention is to be achieved through the following technical solutions:
A kind of end pumping one way row ripple laser amplifier, comprise semiconductor laser, described semiconductor laser is used for providing pumping laser, the right side of described semiconductor laser is provided with coupling pump light focusing system, the upper end of described coupling pump light focusing system and right-hand member are respectively equipped with the laser crystal of incident laser coupling focusing system and piece-wise step doping bonding, and it is heat sink that the surrounding of described laser crystal is provided with the crystal matched.
Further, described coupling pump light focusing system comprises the planoconvex spotlight one, planoconvex spotlight two, planoconvex spotlight three and the level crossing that are set in turn on the right side of described semiconductor laser, described planoconvex spotlight one is identical with the direction of propagation of pumping laser with the convex surface of planoconvex spotlight two, and the convex surface of described planoconvex spotlight three is relative with the convex surface of described planoconvex spotlight two.
Further, described level crossing is the dichroic mirror horizontal by 45 ° of angles.
Further, the front and rear surfaces of described level crossing is coated with the anti-reflection film of 880nm, and the rear surface of described level crossing is coated with the high-reflecting film of 1064nm.
Further, described incident laser coupling focusing system comprise be arranged at level crossing upper end and with the planoconvex spotlight four of plane-parallel and planoconvex spotlight five, the upper end of described planoconvex spotlight five is provided with incident light source, wherein, the convex surface of described planoconvex spotlight five is identical with the direction of propagation of incident light, and the convex surface of described planoconvex spotlight four is relative with the convex surface of described planoconvex spotlight five.
Further, described laser crystal is enclosed with the indium foil that one deck and laser crystal match.
Further, described laser crystal is the piece-wise step doping bonding laser crystal be made up of some sections of laser crystals one, and along pump light transmission direction, the doping content of described laser crystal one increases gradually and first section of laser crystal one undopes.
Further, form laser crystal some sections of laser crystals one length between equal or unequal.
Further, described laser crystal comprises isotropic medium and anisotropic medium, and described isotropic medium includes but not limited to: neodymium-doped yttrium-aluminum garnet Nd:YAG; Described anisotropic medium includes but not limited to: Nd-doped yttrium vanadate crystal Nd:YVO
4, neodymium-doped gadolinium vanadate monocrystalline Nd:GdVO
4.
Further, described semiconductor laser continuous power output is more than 100W, wavelength 880nm, its tail optical fiber core diameter 400 μm, and numerical aperture is 0.22.
Beneficial effect of the present invention is: this apparatus structure is simple, easily operates, and adopt end pumping mode, laser crystal is formed by laser crystal one bonding of multistage Uniform Doped; By reasonably designing doping content and the length of every section of crystal, pump light heat load is on average shared in each section of laser crystal one; Under identical pump power, laser crystal in the present invention than generic homogeneous doping laser crystal internal heat be more evenly distributed, maximum temperaturerise is lower, thermic stress and thermal lensing effect less, thus higher pump power can be born, simultaneously less to the beam quality deterioration of exaggerated laser; On the other hand, the coupling focusing system of pump light and incident laser can realize the mould field coupling of the two, and improve amplification efficiency, compared with conventional laser amplifier, Output of laser power of the present invention is higher, and beam quality is better, and structure is simple, and working stability is reliable.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is the principle schematic of a kind of end pumping one way row ripple laser amplifier according to the embodiment of the present invention;
Fig. 2 is five sections of Doping bonding Nd:YVO of a kind of end pumping one way row ripple laser amplifier described in specific embodiments of the invention
4crystals temperature distributing analog figure;
Fig. 3 is five sections of Doping bonding Nd:YVO of a kind of end pumping one way row ripple laser amplifier described in specific embodiments of the invention
4germ nucleus temperature genesis analysis simulation drawing;
Fig. 4 is absorbing under identical pump power condition, generic homogeneous doping Nd:YVO
4crystals temperature distributing analog figure;
Fig. 5 is absorbing under identical pump power condition, generic homogeneous doping Nd:YVO
4germ nucleus temperature genesis analysis simulation drawing.
In figure:
1, semiconductor laser; 2, planoconvex spotlight one; 3, planoconvex spotlight two; 4, planoconvex spotlight three; 5, level crossing; 6, laser crystal; 7, crystal is heat sink; 8, indium foil; 9, planoconvex spotlight four; 10, planoconvex spotlight five.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain, all belongs to the scope of protection of the invention.
As Figure 1-5, according to a kind of end pumping one way row ripple laser amplifier of the embodiment of the present invention, comprise semiconductor laser 1, described semiconductor laser 1 is for providing pumping laser, the right side of described semiconductor laser 1 is provided with coupling pump light focusing system, the upper end of described coupling pump light focusing system and right-hand member are respectively equipped with the laser crystal 6 of incident laser coupling focusing system and piece-wise step doping bonding, and the surrounding of described laser crystal 6 is provided with the crystal matched heat sink 7.
Described coupling pump light focusing system comprises the planoconvex spotlight 1, planoconvex spotlight 23, planoconvex spotlight 34 and the level crossing 5 that are set in turn on the right side of described semiconductor laser 1, described planoconvex spotlight 1 is identical with the direction of propagation of pumping laser with the convex surface of planoconvex spotlight 23, and the convex surface of described planoconvex spotlight 34 is relative with the convex surface of described planoconvex spotlight 23.
Described level crossing 5 is the dichroic mirror horizontal by 45 ° of angles; The front and rear surfaces of described level crossing 5 is coated with the anti-reflection film of 880nm, and the rear surface of described level crossing 5 is coated with the high-reflecting film of 1064nm; System only uses a stage power amplifier, adopt end pumping mode, pump light enters coupling pump light focusing system by optical fiber or beam shaping system, incident high light beam quality laser to be coupled focusing system through flashlight, reflected by 45 ° of dichroic mirrors, in the same way, coaxially enter in described laser crystal 6 with pump light, its spot size size to be girdled the waist size close to pump light.
Described incident laser coupling focusing system comprise be arranged at level crossing 5 upper end and with the planoconvex spotlight 49 of plane-parallel and planoconvex spotlight 5 10, the upper end of described planoconvex spotlight 5 10 is provided with incident light source, wherein, the convex surface of described planoconvex spotlight 5 10 is identical with the direction of propagation of incident light, and the convex surface of described planoconvex spotlight 49 is relative with the convex surface of described planoconvex spotlight 5 10.
Described laser crystal 6 is enclosed with the indium foil 8 that one deck and laser crystal 6 match; Described laser crystal 6 is the piece-wise step doping bonding laser crystals be made up of some sections of laser crystals one, and along pump light transmission direction, the doping content of described laser crystal one increases gradually and first section of laser crystal one undopes.
Equal or unequal between some sections of laser crystals one length of formation laser crystal 6.
Described laser crystal 6 comprises isotropic medium and anisotropic medium, and described isotropic medium includes but not limited to: neodymium-doped yttrium-aluminum garnet Nd:YAG; Described anisotropic medium includes but not limited to: Nd-doped yttrium vanadate crystal Nd:YVO
4, neodymium-doped gadolinium vanadate monocrystalline Nd:GdVO
4.
Described semiconductor laser 1 continuous power output is more than 100W, wavelength 880nm, its tail optical fiber core diameter 400 μm, and numerical aperture is 0.22.
During concrete use, in order to better understand the technical scheme of the application, with a kind of high power of compact conformation, high light beam quality end pumping one way row ripple laser amplifier for specific embodiment, its structure as shown in Figure 1, comprising:
The semiconductor laser 1 that optical fiber exports, maximum more than continuous power output 100W, wavelength 880nm, its tail optical fiber core diameter 400 μm, numerical aperture NA=0.22, the advantage using the pumping of 880nm wavelength is can Nd
3+directly be energized into the upper energy level of laser from ground state, effectively reduce Excited state effect, fundamentally reduction pumping luminous energy is converted into the ratio shared by heat energy.
The pump light that described semiconductor laser 1 sends is collimated after planoconvex spotlight 1 and planoconvex spotlight 23, focused on by planoconvex spotlight 34 afterwards, through the two-sided level crossing 5 being coated with 880nm anti-reflection film, at the focus spot diameter 1.2 ~ 1.4mm of laser crystal 6 inside; In this coupling pump light system, described planoconvex spotlight 1 is identical with the direction of propagation of pump light with the convex surface of planoconvex spotlight 23; The convex surface of planoconvex spotlight 34 is relative with the convex surface of planoconvex spotlight 23, and this arrangement can reduce the transmission aberration of pump light.
Wherein, described laser crystal 6 adopts five sections of Doping bonding Nd:YVO
4the gain media of crystal is formed, and a axle cuts, and front/rear end is coated with 880nm/1064nm anti-reflection film, and one of them surface band angle of wedge is used for preventing parasitic oscillation, is of a size of 4 × 4 × 30mm
3; Nd:YVO
4crystal has that upper level lifetime is short, stimulated emission cross section is large and the advantage such as natural birefringence, is particularly suitable for the amplification to high repetition frequency, linear polarization pulse laser; But Nd:YVO
4the thermal property of crystal is relatively poor, easily damages under high power pumping condition, so how to improve Nd:YVO
4the power output of laser/amplifier is one of study hotspot of domestic and international association area always, and this is also the problem that the present invention is focused on solving.
In the present embodiment, first section of crystal of gain media does not adulterate, and does not absorb, length 2mm to pump light; The absorption coefficient of second segment crystal to pump light is about 0.045mm
-1, length 6.5mm; The absorption coefficient of 3rd section of crystal to pump light is about 0.06mm
-1, length 6mm; The absorption coefficient of 4th section of crystal to pump light is about 0.09mm
-1, length 7.5mm; The absorption coefficient of 5th section of crystal to pump light is about 0.2mm
-1, length 8mm.For the laser crystal one of every section of Uniform Doped, if crystal length is L, be α to the absorption coefficient of pump light, then in crystal, the light distribution of z place is
I(z)＝I
0exp(-αz)(1)
If ignore the change of pump light beam diameter, the absorbed power of every section of laser crystal a pair pump light is
P
abs＝P
0[1-exp(-αL)](2)
According to above formula, if incident pump power is 100W, the absorbed power of each section of doping laser crystal a pair pump light in this specific embodiment can be calculated all at about 25W; It is worthy of note, the doping content corresponding to absorption coefficient of each section of laser crystal a pair 880nm pump light given by this example is all easily obtain in the manufacturing process of laser crystal one; Although first section of non-doped crystal not absorptive pumping light, but may be used for sharing the pumping heat transmitted from second segment laser crystal one, and the thermal conductivity of laser crystal is far above air, so it significantly can reduce maximum temperature and the thermal stress of doped crystal end face, thus reduce crystal damage risk; Crystal end-face deformation can be reduced again and reduce thermal lensing effect simultaneously, improving beam quality.
Whole Nd:YVO
4crystal 6 side wrap the indium foil 8 of thin layer, be placed in the good fine copper hot and cold water sink 7 of heat conductivility inner, can think the side ambient temperature constant of laser crystal 6, be set to 25 DEG C, the air that former and later two end faces of described laser crystal 6 are poor with thermal conductivity contacts, and can think and be in adiabatci condition; If 20% of pump power is converted into heat energy, finite element method can be used to simulate and to obtain cloth temperature profile in crystal, as shown in Figure 2; Fig. 3 is the genesis analysis simulation drawing of germ nucleus temperature, can see, under the pump power of 100W, 880nm, the maximum temperature of described laser crystal 6 inside only has 71 DEG C; The local maximum temperature of laser crystal 6 appears at the center of the interface of different doped region, has benefited from the doping content of every section of crystal and the appropriate design of length, and the maximum temperature of every section of crystal is all at about 70 DEG C.
Due to longitudinal conductive force of crystal, the Axial Temperature Distribution of described laser crystal 6 is more even, as the germ nucleus temperature within the scope of 2mm ~ 25.2mm in z-axis is all between 60 ~ 71 DEG C, and the germ nucleus temperature in z-axis within the scope of 3mm ~ 17.3mm is all between 65 ~ 71 DEG C especially, this just takes full advantage of the cooling surface area of crystal heat sink 7, make each section of laser crystal one almost evenly share pumping heat load, thus effectively reduce the thermal gradient of laser crystal 6 inside; This not only can reduce the damage risk of laser crystal 6, also can weaken thermal lens, hot-bulb difference effect, make the thermal lens effect of laser crystal 6 closer to perfect lens, thus be conducive to the beam quality keeping exaggerated laser.
On the other hand, first section of non-doped crystal not only effectively reduces the end face maximum temperature of first paragraph doped crystal, and as can be seen from Figure 2, now there is no head face hump effect, this will significantly reduce the thermal lensing effect of whole crystal, thus ensure that the beam quality of exaggerated laser, as a comparison, if it is 0.1mm that the laser crystal 6 of five sections of Doping bondings that this example is provided changes as doping content
-1generic homogeneous doping Nd:YVO
4crystal, the crystal that it provides the absorption efficiency of pump light and this example is identical, makes other condition all constant, can simulate the genesis analysis figure of temperature profile and the germ nucleus temperature obtaining now crystals, respectively as shown in Figure 4 and Figure 5.
Can see, under high power pump effect, heat mainly concentrates on crystal front end, internal temperature exponentially successively decreases to back end from front end face, such crystal is heat sink 7 most of cooling surface area be not just fully utilized, crystal maximum temperature appears at the front end face center that pump light enters crystal, this temperatures as high 131 DEG C, and crystal lateral edges chilling temperature only has 25 DEG C, so large temperature gradient must cause crystal front end face to damage.Even if do not consider crystal damage, Fig. 4 shows now also have obvious end-face deformation effect, and this will significantly strengthen the thermal lensing effect of laser crystal, and incident laser will be focused on consumingly, simultaneously also by with strong spherical aberration effect, and deteriorated beam quality; So no matter be improve laser amplifier power, still keep high beam quality, five sections of Doping bonded crystals of the present embodiment scheme are all more superior than generic homogeneous doping laser crystal performance.
The essence of the present embodiment scheme is that the heat load brought by pump light is on average shared in the laser crystal 6 of multiple Uniform Doped as much as possible, more makes full use of the side cooling surface area of crystal heat sink 7.In theory, the crystal hop count of Doping is more, and this advantage is more obvious; But consider current bonded crystals Manufacturing Techniques level and cost, the scheme that this example provides has more actuality.By comparison diagram 2, Fig. 3 and Fig. 4, Fig. 5, can find out compared to conventional laser amplifier schema, scheme in use the present embodiment can significantly improve the Maximum pumping that laser crystal can bear, thus improve the laser output power of one-stage amplifier, and keep high laser beam quality.
The general pump light beam quality sent by LD is poor, and the angle of divergence at beam waist place is very large; But this angle of divergence can reduce along with the increase of hot spot with a tight waist.In the present embodiment, if the center being in crystal with a tight waist of pump light, spot size with a tight waist is 1.35mm, so the pump spot size of former and later two end faces is 1.65mm, think that the propagation of pump light in laser crystal 6 is collimation if so just can be similar to---use high brightness LD, collimation can be better; Higher pump beam collimation ensure that the validity of analog computation above on the one hand, and the mould field being conducive to increasing pump light and laser is on the one hand overlapping, thus improves energy extraction efficiency.
Incident laser expands through planoconvex spotlight 5 10, and the level crossing 5 being then coated with 1064nm high-reflecting film through planoconvex spotlight 49 and rear surface reflects that to enter laser crystal 6 coaxially, in the same way with pump light inner; Because incident laser beam is of high quality, the angle of divergence is very little, can think directional light when propagating in laser crystal 6.By designing focal length and its distance apart from laser crystal 6 of planoconvex spotlight 49, make the spot diameter size of incident laser in laser crystal 6 at 1.0 ~ 1.2mm, more smaller than pump light hot spot of girdling the waist, this can realize the overlapping to greatest extent of mode of laser field and pumping optical mode field, improves the energy extraction efficiency of laser amplifier.If incident laser directly enters laser crystal 6 without the mode first expanding refocusing, because mould field Duplication is low, high extraction efficiency cannot be obtained.In addition, planoconvex spotlight 49 is relative with the convex surface of planoconvex spotlight 5 10 is conducive to the transmission aberration reducing laser.
In sum, the present embodiment uses high-power LD end pumping five sections of Doping Nd:YVO
4crystal, every section of doped crystal absorbs identical pump power, this heat load that pump light is brought is shared equably to four crystal end-faces, significantly improves the Maximum pumping that laser crystal 6 can bear, and reduces the adverse effect such as thermal lens, thermal aberration simultaneously; By appropriate design, the coupled system regulating pump light and incident laser, the two is made to realize best pattern matching in laser crystal 6 inside, thus raising energy extraction efficiency, finally can realize a kind of high power, the single-pass of high light beam quality, single-stage solid laser amplifier.
The invention provides a kind of high power of compact conformation, high light beam quality end pumping one way row ripple laser amplifier, mainly comprise high-power semiconductor laser diode; Its pump light sent focuses on end face or the inside of laser crystal doped region after collimation, focusing through the dichroic mirror grown tall to pumping wave, the Size-dependent of hot spot with a tight waist is in the design of collimation, focusing system, and position with a tight waist can regulate front and back; Described laser crystal 6 is made up of gain media, and described gain media is formed by the crystal bonding of N section different levels of doping, N >=3, and wherein, first paragraph crystal does not adulterate, all the other every section crystal Uniform Doped, and doping content increases gradually along the pump light direction of propagation; By doping content and the length of appropriate design every section crystal, make each section of doped crystal as far as possible equal with thermal focal length to the absorbed power of pump light; The incident laser of nearly diffraction limit coaxially, in the same way enters laser crystal with pump light after expanding, focusing on, and its spot size in laser crystal is slightly less than pump light and girdles the waist size.High power after amplifying, high light beam quality laser export from the opposite side of crystal.
After pump light enters the laser crystal of above-mentioned design, each section of doped crystal is equal to the absorbed power along pump light, if ignore the change of spot size when pump light is propagated in laser crystal, can think that the central temperature of each section of doped crystal incident end face is equal with thermal gradient distribution.Compared to the traditional scheme that pumping heat load is only born by an end face or two end faces, pumping heat load is shared multiple end face and is born by the present invention equably, more takes full advantage of the cooling surface area of crystal on side face.Under identical pump power, in this programme, the central temperature of each section of crystal incident end face and thermal gradient are minimized, this substantially increases the pump power and unlikely damage laser crystal that can inject on the one hand, also significantly reduce the adverse effect such as thermal aberration, thermal lens on the other hand, make laser still keep high beam quality and spatial stability after high power amplifies.Compared to multi-stage power amplifier scheme, volume of the present invention is less, and structure is simpler, and reliability is higher.
Moreover, incident laser spot size after expanding, focus on and entering laser crystal be slightly less than pump light girdle the waist size be conducive to realize and exaggerated laser and pump light spatial model coupling, thus improve energy extraction efficiency.
The foregoing is only preferred embodiment of the present invention; not in order to limit the present invention; within the spirit and principles in the present invention all; any amendment of doing, equivalent replacement, improvement etc.; as used other wavelength; the pump light of other power, uses gain media of other shape, size, Doping hop count, doping content or Doped ions type etc., all should be included within protection scope of the present invention.
Claims (10)
1. an end pumping one way row ripple laser amplifier, comprise semiconductor laser (1), it is characterized in that, described semiconductor laser (1) is for providing pumping laser, the right side of described semiconductor laser (1) is provided with coupling pump light focusing system, the upper end of described coupling pump light focusing system and right-hand member are respectively equipped with the laser crystal (6) of incident laser coupling focusing system and piece-wise step doping bonding, and the surrounding of described laser crystal (6) is provided with the crystal matched heat sink (7).
2. end pumping one way row ripple laser amplifier according to claim 1, it is characterized in that, described coupling pump light focusing system comprises the planoconvex spotlight one (2), planoconvex spotlight two (3), planoconvex spotlight three (4) and the level crossing (5) that are set in turn in described semiconductor laser (1) right side, described planoconvex spotlight one (2) is identical with the direction of propagation of pumping laser with the convex surface of planoconvex spotlight two (3), and the convex surface of described planoconvex spotlight three (4) is relative with the convex surface of described planoconvex spotlight two (3).
3. end pumping one way row ripple laser amplifier according to claim 2, it is characterized in that, described level crossing (5) is the dichroic mirror horizontal by 45 ° of angles.
4. end pumping one way row ripple laser amplifier according to claim 3, it is characterized in that, the front and rear surfaces of described level crossing (5) is coated with the anti-reflection film of 880nm, and the rear surface of described level crossing (5) is coated with the high-reflecting film of 1064nm.
5. end pumping one way row ripple laser amplifier according to claim 4, it is characterized in that, described incident laser coupling focusing system comprise be arranged at level crossing (5) upper end and with the planoconvex spotlight four (9) of plane-parallel and planoconvex spotlight five (10), the upper end of described planoconvex spotlight five (10) is provided with incident light source, wherein, the convex surface of described planoconvex spotlight five (10) is identical with the direction of propagation of incident light, and the convex surface of described planoconvex spotlight four (9) is relative with the convex surface of described planoconvex spotlight five (10).
6. end pumping one way row ripple laser amplifier according to claim 5, is characterized in that, described laser crystal (6) is enclosed with the indium foil (8) that one deck and laser crystal (6) match.
7. end pumping one way row ripple laser amplifier according to claim 6, it is characterized in that, described laser crystal (6) is the piece-wise step doping bonding laser crystal be made up of some sections of laser crystals one, along pump light transmission direction, the doping content of described laser crystal one increases gradually and first section of laser crystal one undopes.
8. end pumping one way row ripple laser amplifier according to claim 7, is characterized in that, equal or unequal between some sections of laser crystals one length of formation laser crystal (6).
9. end pumping one way row ripple laser amplifier according to claim 8, it is characterized in that, described laser crystal (6) comprises isotropic medium and anisotropic medium, and described isotropic medium includes but not limited to: neodymium-doped yttrium-aluminum garnet Nd:YAG; Described anisotropic medium includes but not limited to: Nd-doped yttrium vanadate crystal Nd:YVO
4, neodymium-doped gadolinium vanadate monocrystalline Nd:GdVO
4.
10. end pumping one way row ripple laser amplifier as claimed in any of claims 1 to 9, it is characterized in that, described semiconductor laser (1) continuous power output is more than 100W, wavelength 880nm, its tail optical fiber core diameter 400 μm, numerical aperture is 0.22.
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Application publication date: 20160203 |