CN101436750A - End-face pump green light laser - Google Patents

Abstract

The invention relates to an end face pump green-light laser which comprises a V-type folding cavity, a coupling and focusing system, a pump unit, a laser crystal, a frequency doubling crystal and a Q adjusting device. The end face pump green-light laser adopts a V-type folding optical circuit structure; basic frequency light produced by a resonant cavity is subjected to frequency doubling through the frequency doubling crystal in the cavity to produce frequency doubling light; and the frequency doubling light is output. The laser has reasonable design, novel conception, a normative process, a compact structure and no pollution, is suitable for industrialized batch production, and can be widely applied to communication, precise electron and other fields.

Description

End-face pump green light laser

Technical field

The present invention relates to design a kind of new laser, particularly relate to a kind of end-face pump green light laser.

Background technology

At present, what domestic most of commercial 532nm laser adopted is line chamber and profile pump structure, though this structure is simple, can obtain bigger laser output, but, can not directly obtain beam quality laser output preferably because type dissymmetrical structure in this chamber own causes laser not export with basic mode, and since thermal lensing effect, laser output energy instability.Simultaneously, because transfer ratio is low, most of pump energy is converted to heat energy, and radiating mode can only adopt water-cooled, causes overall volume huge, and the adding of cooling water has brought hidden danger for safety again.

Summary of the invention

, energy unsettled shortcoming of poor quality for the line chamber laser output beam that overcomes profile pump, make the 532nm laser can the more extensive more stable fields such as industrial processes, manufacturing that are applied to, the present invention adopts a kind of new structure, in fold resonator, insert frequency-doubling crystal, can obtain good beam quality (near basic mode), power stability, can realize that air cooling, wavelength are the end-face pump green light laser of the laser output of 532nm.

The technical solution used in the present invention is: laser resonant cavity adopts the structure of V-type refrative cavity, and laser crystal places refrative cavity linear arm, close corner, is convenient to pump light pumping laser crystal; Frequency-doubling crystal places another arm of refrative cavity, close outgoing mirror place, is convenient to fundamental frequency light and carries out frequency multiplication generation frequency doubled light in the chamber; Adopt refrative cavity can make laser crystal be in the center of symmetrical structure, thermal lensing effect reduces half, and elongate chamber is long effectively, thereby reaches the purpose that improves beam quality, power stability output.By the coupling focus lamp, the basic mode size of resonant cavity is identical therewith in the laser crystal interior size for pump light; The coupling focus lamp adopts Collapsible structure, is convenient to regulate that pump light is with a tight waist overlaps with the basic mode position, thereby makes laser energy can concentrate on basic mode, and beam quality is improved greatly, and energy has also obtained maximum utilization.This structure can obtain higher light-light conversion efficiency, has reduced the generation of heat, thereby can adopt air-cooled structure.Concrete technology implementation scheme is as follows:

The resonant cavity of laser is a V-type refrative cavity structure, and its light path is a V-type, and angle is made of total reflective mirror 2, chamber mirror 6 and outgoing mirror 13 along optical axis 1 less than 21 degree; Laser crystal 5 is positioned on the optical axis 1 of close chamber mirror 6; Frequency-doubling crystal 14 is positioned near on the optical axis 1 of outgoing mirror 13, and the fundamental frequency light 4 that shakes in resonant cavity by frequency-doubling crystal 14 nonlinear effect takes place, and produces frequency doubled light 15, and frequency doubled light 15 is from the output of outgoing mirror 13 outputs formation laser; Adopt optical fiber 12 pumpings; Pump unit is made of optical fiber 12 and coupling focus lamp 10, and pump light 11 focuses on by coupling focus lamp 10 along optical axis 1 and incides laser crystal 5 inside from V-type refrative cavity corner chamber mirror 6; In the chamber, insert active or passive Q-adjusted device 3 on the optical axis and realize the pulse output of laser; Laser crystal 5 can be Nd-doped yttrium vanadate Nd:YVO ₄Crystal, neodymium-doped yttrium-aluminum garnet Nd:YAG crystal, neodymium-doped vanadic acid gadolinium Nd:GdVO ₄Crystal, mix laser crystals such as ytterbium yttrium-aluminium-garnet Yb:YAG crystal, neodymium-doped yttrium aluminate Nd:YAP crystal, neodymium-doped potassium-gadolinium Nd:KGW crystal, neodymium-doped yttrium-fluoride lithium Nd:YLF crystal; Frequency-doubling crystal 14 can be potassium titanium oxide phosphate KTP, nonlinear crystals such as three lithium borate LBO, barium metaborate BBO.

Good, the power stability of the 532nm laser beam quality that the invention has the beneficial effects as follows output, can realize air cooling, overall volume is small and exquisite, can be applied to every field such as industrial processes, scientific research, medical treatment, military affairs, be applicable to the various occasions such as laser labelling, material surface or inner engraving, retrofit, cutting, electronic welding, pumping, laser positioning, laser ranging of various material surfaces.

Description of drawings

Figure 1 shows that the laserresonator schematic diagram, among the figure, 1. optical axis, 2. total reflective mirror, 3. adjusting Q crystal, 4. fundamental frequency light, 5. laser crystal, 6. chamber mirror, 7,8,9. lens, 10. coupling focusing system, 11. pump light, 12. optical fiber, 13. outgoing mirrors, 14. frequency-doubling crystals, 15. frequency doubled lights.

Embodiment

The present invention in conjunction with the accompanying drawings 1, and be described in detail as follows to its technical scheme: total reflective mirror 2, chamber mirror 6 and outgoing mirror 13 have constituted laserresonator; Laser crystal 5 is placed on the optical axis 1 of close chamber mirror, is positioned at the structure centre of equivalent cavity; Lens 7,8,9 are formed coupling focusing system 10; Pump light 11 incides laser crystal 5 inside through overcoupling focusing system 10, produces fundamental frequency light 4; Adjusting Q crystal 3 is placed on the optical axis 1, produces pulse laser; Fundamental frequency light 4 vibrates in resonant cavity, at frequency-doubling crystal 14 nonlinear effect takes place, and frequency multiplication produces double-frequency laser 15, from outgoing mirror 13 outputs; Adopt optical fiber 12 pumpings; Pump unit is made of optical fiber 12 and coupling focus lamp 10, and pump light 11 focuses on by coupling focus lamp 10 along optical axis 1 and incides laser crystal 5 inside from V-type refrative cavity corner chamber mirror 6; In the chamber, insert active or passive Q-adjusted device 3 on the optical axis and realize the pulse output of laser; Laser crystal 5 can be Nd-doped yttrium vanadate Nd:YVO ₄Crystal, neodymium-doped yttrium-aluminum garnet Nd:YAG crystal, neodymium-doped vanadic acid gadolinium Nd:GdVO ₄Crystal, mix laser crystals such as ytterbium yttrium-aluminium-garnet Yb:YAG crystal, neodymium-doped yttrium aluminate Nd:YAP crystal, neodymium-doped potassium-gadolinium Nd:KGW crystal, neodymium-doped yttrium-fluoride lithium Nd:YLF crystal; Frequency-doubling crystal 14 can be potassium titanium oxide phosphate KTP, three lithium borate LBO or barium metaborate BBO nonlinear crystal.

The present invention utilizes the refrative cavity type to regulate the outgoing mirror position to realize that resonant cavity reduces thermal lensing effect about the symmetry of laser crystal, the basic mode that utilizes the coupling focus lamp to regulate pump light size with a tight waist and position and resonant cavity simultaneously is complementary, make most of pump energy run on basic mode, thereby obtain the laser output of good beam quality power stability.In the process that laser vibrates in resonant cavity, form various multi-form stable distributions in the light intensity on the beam cross-section. this stable distribution on beam cross-section, the transverse mode that is called laser beam, be called for short transverse mode, fundamental transverse mode position of each point on the cross section of laser beam is mutually identical, beam quality is best, is called for short basic mode.Pump light is beaten at crystals, forms heat in intracrystalline uneven distribution, and refractive index generation minor variations, the optical characteristics of crystal are equivalent to lens, are referred to as thermal lens.The thermal lens that crystal can be equivalent to a focal length in resonant cavity be f, thermal lens f and pump light ω with a tight waist square is directly proportional, promptly

$f=\frac{\mathrm{\π}{K}_c{\mathrm{\ω}}^2}{P_{\mathrm{ph}}(\mathrm{dn}/\mathrm{dT})}\·\frac{1}{1-\exp (-\mathrm{\αl})},$

Pyrogenicity power P in the formula _PhCan be expressed as P _Ph=P _In* (1-η)=P ₀* T ₀In * (1-η) formula, P ₀Be total pump power, P _InBe the pump power of input crystal, T ₀Transmitance for coupled system; η is total slope efficiency of laser, K _cBe thermal conductivity, dn/dT is laser crystal refractive index and variation of temperature rate, and l is a crystal length, and α is the absorption coefficient of crystal; In order to reduce thermal lens, just must increase pump light size with a tight waist; But for certain resonant cavity, the big or small ω of basic mode on crystal ₀₀Be certain, concentrate on basic mode, just must make pump light size with a tight waist and basic mode size satisfy ω ≈ ω in order to make laser energy ₀₀, so pump light the size with a tight waist of crystals will be as much as possible less than and near the basic mode size.For size and the certain pumping of energy, the thermal lens f size of generation also is certain.As shown in Figure 3, according to the optical delivery matrix of lens, the thermal lens transmission matrix of refrative cavity is

$\left[\begin{array}{cc}1& 0\\ -\frac{1}{f}& 1\end{array}\right],$

And the equivalent thermal lens matrix of line chamber is

$\left[\begin{array}{cc}1& 0\\ -\frac{1}{f}& 1\end{array}\right]\×\left[\begin{array}{cc}1& 0\\ -\frac{1}{f}& 1\end{array}\right]=\left[\begin{array}{cc}1& 0\\ -\frac{2}{f}& 1\end{array}\right],$

Its equivalent thermal lens is The thermal lens of the refrative cavity of same equivalent length has only half of line chamber, and its thermal lensing effect obviously alleviates.For identical pumping, adopt refrative cavity can significantly reduce the thermal lensing effect of resonant cavity.From reproducing vibration, the transmission matrix of the equivalent cavity of refrative cavity is fundamental frequency light in resonant cavity

$\left[\begin{array}{cc}A& B\\ C& D\end{array}\right]=\left[\begin{array}{cc}1& L\\ 0& 1\end{array}\right]\×\left[\begin{array}{cc}1& 0\\ -\frac{1}{f}& 1\end{array}\right]\×\left[\begin{array}{cc}1& L\\ 0& 1\end{array}\right]\×\left[\begin{array}{cc}1& L\\ 0& 1\end{array}\right]\×\left[\begin{array}{cc}1& 0\\ -\frac{2}{f}& 1\end{array}\right]\×\left[\begin{array}{cc}1& L\\ 0& 1\end{array}\right],$

Fundamental frequency light can be described with the q parameter, $\frac{1}{q}=-z+\mathrm{\ωi},$ The q parameter of mirror place, refrative cavity chamber fundamental frequency light satisfies

$q=\frac{A+\mathrm{qB}}{C+\mathrm{qD}},$

Can calculate the basic mode size of refrative cavity thus at laser crystal 5 centers.

According to above principle, the present invention is directed to different laser output powers and actual service conditions, calculate and choose the optimized parameter of resonant cavity, make power output satisfy instructions for use not needs increase under the situation of other device, can obtain good beam quality, the stable laser of output.Concrete scheme is as follows:

(1) as shown in Figure 2, the parameter of optical fiber output is that bright dipping bore (promptly with a tight waist) is ω _Fiber=0.4mm, numerical aperture NA=0.22, by the coupling focus lamp, the optical parametric of pump light becomes ω=0.8mm with a tight waist, numerical aperture NA=0.11, adopt 3 fairly simple lens arrangements just can realize, concrete example is as follows: 3 identical f=30mm of lens parameter, put according to shown in Figure 2, the optical fiber exiting surface is a=12.45mm to the distance of lens 9, lens 9 and lens 8 are close together, light beam between lens 8 and the lens 7 is similar to directional light like this, and the change of lens 7 position on optical axis does not influence the size with a tight waist and the operating distance (the lens exiting surface is to distance with a tight waist) of bright dipping substantially, and the coupling focus lamp just can be realized focusing effect and the operating distance b=30mm of 1:2.

(2) parameter of resonant cavity is decided, and its basic mode has also been decided at the diameter of crystals.Choose suitable cavity, the basic mode size is complementary with pump light, laser energy can concentrate on basic mode.The specific design example is as follows: put laser each several part device according to Fig. 1 on optical axis, comprise total reflective mirror, chamber mirror, outgoing mirror, laser crystal and coupling focus lamp; Total reflective mirror is 150mm to the distance of germ nucleus, and the chamber mirror is 20mm to the distance of germ nucleus, and outgoing mirror is 130mm to the distance of chamber mirror, and the corner angle of v-shaped cavity is 20 degree; Coupling focus lamp light output end is apart from laser crystal center 30mm.According to the thermal lens theory, be 20W at pump power, pumping is with a tight waist under the condition of 0.8mm, and its equivalent thermal lens is f=458mm; According to beam transformation matrix, can calculate when the equivalent cavity length of refrative cavity is 300mm, basic mode is ω in the size of crystals ₀₀=0.75mm, the big or small ω at crystals is close with pump light.Under this condition, can access that output beam quality is good, 4 vibrations of the fundamental frequency light of power stability.

(3) insert frequency-doubling crystal 14 near outgoing mirror 13 places on optical axis 1, nonlinear effect takes place by frequency-doubling crystal in the fundamental frequency light 4 that shakes in resonant cavity, produces frequency doubled light 15, and frequency doubled light is from the output of outgoing mirror 13 outputs formation laser.

(4) according to practical application, need in the chamber, add other optics, for example, in the chamber, increase Q-switching device 3 in order to obtain pulse laser.

(5) according to practical application, laser crystal 5 can be Nd-doped yttrium vanadate Nd:YVO ₄Crystal, neodymium-doped yttrium-aluminum garnet Nd:YAG crystal, neodymium-doped vanadic acid gadolinium Nd:GdVO ₄Crystal, mix ytterbium yttrium-aluminium-garnet Yb:YAG crystal, neodymium-doped yttrium aluminate Nd:YAP crystal, neodymium-doped potassium-gadolinium Nd:KGW crystal, neodymium-doped yttrium-fluoride lithium Nd:YLF crystal laser crystal.

(6) according to practical application, frequency-doubling crystal 14 can be potassium titanium oxide phosphate KTP, three lithium borate LBO, barium metaborate BBO nonlinear crystal.

Claims (7)

1. novel end-face pump green light laser, constitute by resonant cavity, laser crystal, frequency-doubling crystal and pump unit, it is characterized in that: the resonant cavity of laser is a V-type refrative cavity structure, its light path is a V-type, angle is made of total reflective mirror (2), chamber mirror (6) and outgoing mirror (13) along optical axis (1) less than 21 degree; Laser crystal (5) is positioned near on the optical axis (1) of chamber mirror (6); Frequency-doubling crystal (14) is positioned near on the optical axis (1) of outgoing mirror (13), the fundamental frequency light (4) that shakes in resonant cavity is by frequency-doubling crystal (14), nonlinear effect takes place, produce frequency doubled light (15), frequency doubled light (15) forms laser output from outgoing mirror (13) output; Adopt optical fiber (12) pumping; Pump unit is made of optical fiber (12) and coupling focus lamp (10), and pump light (11) focuses on by coupling focus lamp (10) along optical axis (1) and incides laser crystal (5) inside from V-type refrative cavity corner chamber mirror (6); In the chamber, insert active or passive Q-adjusted device (3) on the optical axis and realize the pulse output of laser.

2. end-face pump green light laser according to claim 1 is characterized in that, laser crystal (5) is positioned on the optical axis (1) near the chamber mirror, is positioned at the structure centre of equivalent cavity, according to suitable deviation structure center, practical application crystal position.

3. end-face pump green light laser according to claim 1 is characterized in that, adopts the pumping coupling focus lamp (10) of the structure of 3 two groups of combination of lensess; First set of contact lenses is close to by two lens (8) (9) and is formed, and effect collimates pump light (11); Second set of contact lenses has only a slice lens (7), and effect is that the pump light behind the collimation is focused on; Distance is adjustable between two groups of lens, and operating distance and focusing effect are constant.

4. end-face pump green light laser according to claim 1, it is characterized in that laser crystal (5) can be Nd-doped yttrium vanadate crystal, neodymium-doped yttrium-aluminum garnet crystal, neodymium-doped vanadic acid gadolinium crystal, yttrium aluminum garnet crystal with ytterbium doping, neodymium-doped yttrium aluminate crystal, neodymium-doped potassium-gadolinium crystal or neodymium-doped yttrium-fluoride crystalline lithium laser crystal.

5. end-face pump green light laser according to claim 1 is characterized in that, frequency-doubling crystal (14) can be potassium titanium oxide phosphate, three lithium borates or barium metaborate nonlinear crystal.

6. end-face pump green light laser according to claim 1 is characterized in that, chamber mirror (6) minute surface normal and optical axis (1) angle are 10 degree; The angle of V-type light path is 2 times of above-mentioned angle.

7. end-face pump green light laser according to claim 1 is characterized in that, Q-switching device (3) can be active or passive Q-adjusted device.

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