CN1595737A - A laser rod thermal lens effect compensation apparatus and compensation method - Google Patents
A laser rod thermal lens effect compensation apparatus and compensation method Download PDFInfo
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- CN1595737A CN1595737A CN 200410025705 CN200410025705A CN1595737A CN 1595737 A CN1595737 A CN 1595737A CN 200410025705 CN200410025705 CN 200410025705 CN 200410025705 A CN200410025705 A CN 200410025705A CN 1595737 A CN1595737 A CN 1595737A
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Abstract
Disclosed is a compensating device and compensating method for laser rod thermal lens effect. The apparatus includes a concave lens and a convex lens behind laser rod, the center of concave lens has a invariable distance to end plane of convex lens, convex lens has moving mechanism, three optical axises separately from concave lens, convex lens and laser rod are coincident. Calculate or measure focal distance of laser rod which reaches thermal equilibrium under different average powder of pumping, and acquire the distance adjusted between concave lens and convex lens, then move convex lens towards concave lens to complete compensation beam divergence angle increase of optical maser caused by thermal lens effect, damage of laser working substance caused by self - focusing effect can be avoided totally, with no large influence to output power of laser, as well as that of single pulse of output power.
Description
Technical field
The present invention relates to the thermal lensing effect of laser bar in a kind of solid state laser, especially relate to a kind of laser bar thermal lens effect compensation arrangement and compensation method.
Background technology
Existing solid state laser is the absorptive pumping light energy in operation process, except that fraction is exported with laser mode, most of energy change heat into and are deposited on makes it produce temperature rise in the working-laser material, constantly repeating under pumping and the conduction of heat, temperature gradient constantly increases in the operation material, takes away up to heating power and cooling fluid to reach heat balance when heat equates.In the operation material existence of temperature gradient make originally refractive index fully uniformly operation material become the class lens medium, light beam focuses on after by operation material, is commonly called as to be thermal self-focusing.Under the situation of symmetric pump, garden cylindricality laser bar becomes the class globe lens, and its primary flat is called thermal focal length to the distance of focus.Thermal self-focusing not only makes the laser-beam divergence angle increase sharply, and even more serious is can be in the inner real focus that produces of operation material, and it will produce laser damage at material internal.In order to alleviate the influence of thermal lensing effect, extensively adopt at present the operation material end face is worn into concave surface compensating, but can only the specific thermal lensing effect under the particular pump power be compensated Laser Devices.For this reason, people manage to seek the compensation that the ancillary relief device that adds is realized thermal lensing effect, as disclosing a kind of novel thermal insensitive cavity in No. 02266147.6 Chinese utility model patent specification that on August 27th, 2003, bulletin was authorized, between solid laser medium (being equivalent to the laser bar among the present invention) and outgoing mirror, an offset lens driven by stepper motors is set, offset lens is moved forward and backward the position of adjusting offset lens according to the size of solid laser medium power by step motor drive.The applied optical principle of this compensation arrangement is to make the distance between laser medium and the offset lens remain thermal focal length and offset lens focal length sum, even thermal lens and offset lens form Kepler telescope, reach the thermal lensing effect of compensation solid laser medium thus, make unstable cavity become stable cavity, high-power laser output has the purpose of stable preferably and beam quality.But also there is following problem in above-mentioned compensation arrangement: the compensation method of this compensation arrangement is that to make the rod and the distance of lens equal " thermal focal length and focal length of lens sum " be thermal lens and lens formation Kepler telescope, because the thermal effect of rod is the class lens, adopt the impossible full remuneration of einzel lens; This compensation arrangement has only when thermal focal length is very little, " thermal focal length and focal length of lens sum " can be the practical laser device and adopts, when thermal focal length big (as several meters), " thermal focal length and focal length of lens sum " is quite big, and being difficult to is the employing of practical laser device; In addition, add lens in the chamber after, make laser can't carry out single run.
Summary of the invention
Technical problem to be solved by this invention is to provide a kind of laser bar thermal lens effect compensation arrangement and compensation method at above-mentioned prior art present situation, can realize that the thermal self-focusing effect to the laser bar in the solid state laser is carried out full remuneration under the different pump powers.
The present invention solves the problems of the technologies described above the technical scheme that is adopted: a kind of laser bar thermal lens effect compensation arrangement, it comprises concavees lens and convex lens that are arranged on behind the laser bar, the center of described concavees lens and the end face of described laser bar are a fixing distance, described convex lens are provided with position travel mechanism, and the optical axis three of the optical axis of described concavees lens, the optical axis of described convex lens and described laser bar overlaps.
The focal length value of described concavees lens is less than the focal length value of described convex lens.
The ultimate range that described convex lens move is the focal length that the focal length of described convex lens deducts described concavees lens.
Described concavees lens are thin sphere concavees lens, and described convex lens are thin spherical convex lens.
The present invention solves the problems of the technologies described above the another technical scheme that is adopted: a kind of laser bar thermal lens effect compensation method, comprise the steps, step 1: after concavees lens and convex lens are arranged on the output end face of laser bar, make the optical axis of described concavees lens and described convex lens and the optical axis coincidence of described laser rod by adjustment, the end face that makes the center of described concavees lens and described laser bar is a fixing distance, and to adjust distance between described concavees lens and the convex lens be the focal length that the focal length of described convex lens deducts described concavees lens; Step 2: determine the thermal focal length of described laser bar when different pumping average powers are issued to heat balance; Step 3: calculate the adjustment distance between described convex lens and the described concavees lens, and make described convex lens reduce direction to move described adjustment distance to two lens distance; Step 4: in the operation process of laser, move described convex lens and dynamically revise.
Thermal focal length in the described step 2 obtains by calculating according to following formula,
Adjustment distance in the described step 3 is calculated according to following formula and is obtained,
Wherein: Δ d-is the adjustment distance that convex lens move, and n-is the refractive index of laser bar, and f-is a thermal focal length, f
1-be the focal length of concavees lens, d
1-be the distance of concavees lens and laser bar output end face, L-is the length of laser bar, "-" expression reduces direction along two lens distance and regulates.
Dynamic correction in the described step 4 is to move described convex lens to make the far-field spot and the near field hot spot of laser output approaching.
Compared with prior art, the invention has the advantages that the phenomenon do compensation fully that can increase to the caused laser optical beam divergence angle of thermal lensing effect that laser bar produces under any pump power, can avoid the damage of the caused working-laser material of thermal self-focusing phenomenon fully, and can not produce big influence laser output power; And when the laser single pulse was worked, compensation arrangement was equal to a Galileo beam expanding telescope, thereby can not influence the running of laser; Concavees lens and convex lens by selection has the different focal parameter can not be subjected to the influence of thermal focal length size, realize the full remuneration to thermal lensing effect.Compensation arrangement of the present invention can be arranged in the optical resonator of laser and outside the optical resonator, also can be arranged on the back as the laser bar of amplifier.
Description of drawings
Fig. 1 is the structural representation of the embodiment of the invention one;
Fig. 2 is the structural representation of offset lens of the present invention;
Fig. 3 is the structural representation of the embodiment of the invention two.
Embodiment
Embodiment describes in further detail the present invention below in conjunction with accompanying drawing.
Embodiment one: as depicted in figs. 1 and 2, a kind of laser bar thermal lens effect compensation arrangement, comprise laser bar 1, be respectively arranged with the optical resonator of completely reflecting mirror 2 and laser output mirror 3 formation lasers at the two ends of laser bar 1, concavees lens 4 and convex lens 5 are arranged in the optical resonator behind the laser bar 1, and the end face of the center of concavees lens 4 and laser bar 1 is one fixing apart from d
1, convex lens 5 are provided with position travel mechanism, and concavees lens 4 are to have focal distance f
1Thin sphere concavees lens, convex lens 5 are to have focal distance f
2Thin spherical convex lens, the focal length value f of concavees lens 4
1Focal length value f less than convex lens 5
2, the ultimate range that convex lens 5 move is the focal distance f of convex lens 5
2Deduct the focal distance f of concavees lens 4
1, the optical axis of the optical axis of concavees lens 4, convex lens 5 and the optical axis three of laser bar 1 overlap.
Embodiment two: as shown in Figure 3, a kind of laser bar thermal lens effect compensation arrangement, comprise laser bar 1, be respectively arranged with the optical resonator of completely reflecting mirror 2 and laser output mirror 3 formation lasers at the two ends of laser bar 1, concavees lens 4 and convex lens 5 are arranged on outside the optical resonator behind the laser bar 1, and the end face of the center of concavees lens 4 and laser bar 1 is one fixing apart from d
1, convex lens 5 are provided with position travel mechanism, and concavees lens 4 are to have focal distance f
1Thin sphere concavees lens, convex lens 5 are to have focal distance f
2Thin spherical convex lens, the focal length value f of concavees lens 4
1Focal length value f less than convex lens 5
2, the ultimate range that convex lens 5 move is the focal distance f of convex lens 5
2Deduct the focal distance f of concavees lens 4
1The optical axis three of the optical axis of the optical axis of concavees lens 4, convex lens 5 and laser bar 1 overlaps, be provided with second laser bar 1 ' as amplifier in the back of convex lens 5, second laser bar 1 ' the back be provided with one second concavees lens 4 ' and one second convex lens 5 ', second concavees lens 4 ' center and second laser bar 1 ' end face be one fix apart from d
1', second convex lens 5 ' be provided with position travel mechanism, second concavees lens 4 ' be to have focal distance f
1' thin sphere concavees lens, second convex lens 5 ' be to have focal distance f
2' thin spherical convex lens, second concavees lens 4 ' focal length value f
1' less than second convex lens 5 ' focal length value f
2', the ultimate range of second convex lens 5 ' move be second convex lens 5 ' focal distance f
2' deduct second concavees lens 4 ' focal distance f
1', second concavees lens 4 ' optical axis, second convex lens 5 ' optical axis and second laser bar 1 ' the optical axis three overlap.
Embodiment three: a kind of laser bar thermal lens effect compensation method, comprise the steps, step 1: after concavees lens 4 and convex lens 5 are arranged on the output end face of laser bar 1, make the optical axis of concavees lens 4 and convex lens 5 and the optical axis coincidence of laser bar 1 by being similar to the such adjusting device of four-dimensional optical adjusting frame (figure show), the output end face that makes the center of concavees lens 4 and laser bar 1 be one fix apart from d
1, and the distance of adjusting between concavees lens 4 and the convex lens 5 is the focal distance f of convex lens 5
2Deduct the focal distance f of concavees lens 4
1Step 2: according to following formula
Determine the thermal focal length f of laser bar 1 when different pumping average powers are issued to heat balance by calculating, wherein: the f-thermal focal length, the material coefficient of heat conduction of κ-laser bar 1, the material thermal refractive index coefficient of β-laser bar 1, the heating efficiency of χ-Laser Devices, be the ratio of heating power and pumping average power, Wp-unit volume working-laser material pumping average power, the length of L-laser bar 1, the stress thermo-optical coeffecient of P-working-laser material; Step 3: according to following formula
Calculate the adjustment distance, delta d between convex lens 5 and the concavees lens 4, and make convex lens 5 reduce direction to two lens distance to move and adjust distance, delta d, wherein: Δ d-is the adjustment distance that convex lens 5 move, and n-is the refractive index of laser bar 1, and f-is a thermal focal length, f
1-be the focal length of concavees lens 4, d
1-be the center of concavees lens 4 and the distance of laser bar 1 output end face, L-is the length of laser bar 1, "-" expression reduces direction along two lens distance and regulates; Step 4: mix computer, Intelligent Laser power supply and stepping motor, in the operation process of laser, the far-field spot of laser output is dynamically revised with the near field hot spot is approaching by mobile convex lens 5.
We are that example is implemented a concrete scheme with Fig. 3: laser bar 1 is Nd
3+Glass laser rod, it is of a size of φ 8 * 200, and volume is 10cm
3, the laser bar 1 that the amplifier that is provided with behind laser uses ' be Nd
3+Glass laser rod, it is of a size of φ 12 * 300, and volume is 34cm
3, laser be provided with first concavees lens 4 and first convex lens 5, behind amplifier, be provided with second concavees lens 4 ' and second convex lens 5 ', the concentration of glass laser rod is 2 * 10
20/ cm
3The N3122 phosphate laser glass, its heating efficiency χ=8%, thermal refractive index coefficient β=-4.3 * 10
-6/ ℃, the stress thermo-optical coeffecient is P=5.8 * 10
-6/ ℃, the coefficient of heat conduction is κ=0.56W/m ℃.Laser system work repetition rate is 2Hz, and the every pulse pump energy of oscillator is 200J, and the pumping average power density is 40W/cm
3, calculating thermal focal length is 117cm; The every pulse pump energy of amplifier is 1000J, and the pumping average power density is 59W/cm
3, calculating its thermal focal length is 53cm.Two compensation arrangement parameters are set to the focal distance f of first concavees lens 4 respectively
1=10cm, the focal distance f of first convex lens 5
2=15cm, second concavees lens 4 ' focal distance f
1'=10cm, second convex lens 5 ' focal distance f
2'=15cm.
Regulate the optical axis of first concavees lens 4, first convex lens 5 and second concavees lens 4 ', second convex lens 5 ' optical axis and laser system optical axis coincidence, first concavees lens 4 are that the heart is apart from laser bar 1 output d
1=30cm, second concavees lens 4 ' centre-to-centre spacing amplifier laser bar 1 ' output end face d
2=5cm, when the laser system pulse turns round, d=f
2-f
1=50mm, d '=f
2'-f
1'=50mm, i.e. Δ d=0, Δ d '=0, compensation arrangement uses as beam expanding telescope, and it expands bundle multiplying power is 1.5.When laser system turns round with above-mentioned condition of work repetition rate, calculate the compensation arrangement regulated quantity and be respectively Δ d=-14.1mm and Δ d '=-35.1mm, the 50mm when promptly the lens distance of two compensation arrangements is from Galilean telescope is reduced to 35.9mm and 14.9mm respectively.Device is turned round under above-mentioned condition of work, in operation process, do dynamically fine setting, export closely, can think when far-field spot is measure-alike and realize full remuneration until oscillator and amplifier.
In the above embodiments, we also can change into mobile concavees lens with mobile convex lens, do corresponding the adjustment but tackle computing formula this moment, and it calculates the situation that is not so good as mobile convex lens and comes easyly.
The present invention is applicable to the solid state laser of various different medium materials, comprises continuously or the YAG laser of high repetition frequency, also is applicable in " laser generation-amplification system " of more complicated simultaneously.
Claims (8)
1, a kind of laser bar thermal lens effect compensation arrangement, it is characterized in that it comprises concavees lens and convex lens that are arranged on behind the laser bar, the center of described concavees lens and the end face of described laser bar are a fixing distance, described convex lens are provided with position travel mechanism, and the optical axis three of the optical axis of described concavees lens, the optical axis of described convex lens and described laser bar overlaps.
2, a kind of laser bar thermal lens effect compensation arrangement as claimed in claim 1 is characterized in that the focal length value of the focal length value of described concavees lens less than described convex lens.
3, a kind of laser bar thermal lens effect compensation arrangement as claimed in claim 2 is characterized in that ultimate range that described convex lens move is the focal length that the focal length of described convex lens deducts described concavees lens.
4, a kind of laser bar thermal lens effect compensation arrangement as claimed in claim 1 is characterized in that described concavees lens are thin sphere concavees lens, and described convex lens are thin spherical convex lens.
5, a kind of laser bar thermal lens effect compensation method, comprise the steps, step 1: after concavees lens and convex lens are arranged on the output end face of laser bar, make the optical axis of described concavees lens and described convex lens and the optical axis coincidence of described laser bar by adjustment, the end face that makes the center of described concavees lens and described laser bar is a fixing distance, and to adjust distance between described concavees lens and the convex lens be the focal length that the focal length of described convex lens deducts described concavees lens; Step 2: determine the thermal focal length of described laser bar when different pumping average powers are issued to heat balance; Step 3: calculate the adjustment distance between described convex lens and the described concavees lens, and make described convex lens reduce direction to move described adjustment distance to two lens distance; Step 4: in the operation process of laser, move described convex lens and dynamically revise.
6, a kind of laser bar thermal lens effect compensation method as claimed in claim 5 is characterized in that the thermal focal length in the described step 2 obtains by calculating according to following formula,
Wherein: the f-thermal focal length, the coefficient of heat conduction of κ-laser material, the thermal refractive index coefficient of β-laser material, the heating efficiency of x-Laser Devices, be the ratio of heating power and pumping average power, Wp-unit volume working-laser material pumping average power, the length of L-laser bar, the stress thermo-optical coeffecient of P-working-laser material.
7, a kind of laser bar thermal lens effect compensation method as claimed in claim 5 is characterized in that the adjustment distance in the described step 3 is calculated acquisition according to following formula,
Wherein: Δ d-is the adjustment distance that convex lens move, and n-is the refractive index of laser bar, and f-is a thermal focal length, f
1-be the focal length of concavees lens, d
1-be the distance of concavees lens and laser bar output end face, L-is the length of laser bar, "-" expression reduces direction along two lens distance and regulates.
8, a kind of laser bar thermal lens effect compensation method as claimed in claim 5 is characterized in that the dynamic correction in the described step 4 is to move described convex lens to make the far-field spot and the near field hot spot of laser output approaching.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105514775A (en) * | 2016-01-06 | 2016-04-20 | 中国科学院上海光学精密机械研究所 | High-energy Ti sapphire multipass amplifier thermal lens effect inhibition method |
| CN109683306A (en) * | 2019-01-31 | 2019-04-26 | 中国工程物理研究院激光聚变研究中心 | It is a kind of for overcoming the wavefront control method of thermal lensing effect |
| CN113432837A (en) * | 2021-06-07 | 2021-09-24 | 中国科学院上海光学精密机械研究所 | Device and method for measuring focal length of crystal thermal lens |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101414727B (en) * | 2008-12-05 | 2010-06-02 | 长春理工大学 | Self-adaptive equalization thermal lens laser resonant cavity for crystal lens |
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| DE3164024D1 (en) * | 1980-01-21 | 1984-07-19 | Commw Of Australia | Birefringence coupled high average power laser |
| GB8912765D0 (en) * | 1989-06-02 | 1989-07-19 | Lumonics Ltd | A laser |
| JP2917413B2 (en) * | 1990-05-23 | 1999-07-12 | ソニー株式会社 | Solid state laser oscillator |
| JP4613272B2 (en) * | 2000-05-10 | 2011-01-12 | 独立行政法人理化学研究所 | Laser resonator and adjustment method thereof |
| EP1168532A1 (en) * | 2000-06-23 | 2002-01-02 | Universität Bern | Method for compensating thermo-optic effects |
| CN2482750Y (en) * | 2001-05-31 | 2002-03-20 | 北京工业大学 | Large power semi-conductor laser longitudinal pumping solid laser |
| CN2569375Y (en) * | 2002-08-08 | 2003-08-27 | 上海市激光技术研究所 | New thermal stable chamber |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105514775A (en) * | 2016-01-06 | 2016-04-20 | 中国科学院上海光学精密机械研究所 | High-energy Ti sapphire multipass amplifier thermal lens effect inhibition method |
| CN105514775B (en) * | 2016-01-06 | 2018-06-19 | 中国科学院上海光学精密机械研究所 | The suppressing method of high energy Ti∶Sapphire laser multi-pass amplifier thermal lensing effect |
| CN109683306A (en) * | 2019-01-31 | 2019-04-26 | 中国工程物理研究院激光聚变研究中心 | It is a kind of for overcoming the wavefront control method of thermal lensing effect |
| CN113432837A (en) * | 2021-06-07 | 2021-09-24 | 中国科学院上海光学精密机械研究所 | Device and method for measuring focal length of crystal thermal lens |
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