CN103050871B - Laser gain rod as well as laser oscillator and laser amplifier comprising the same - Google Patents

Abstract

The invention discloses a laser gain rod used for pump homogenization, and belongs to the technical field of the laser. The cross section of the laser gain rod is non-rotationally symmetric, and side surface polishing and end surface polishing are carried out; after pump light is injected from the side surface or the end surface of the laser gain rod, total reflection is generated on the side surface of the laser gain rod; therefore, the pump light is always constrained in the laser gain rod to be transmitted; meanwhile, because the non-rotational symmetry of the side surface, the pump light unlikely forms hollow spiral light, and therefore the pump light is evener in space distribution; in addition, the laser gain rod used for the pump homogenization has a low doping density and a big cooling surface area; therefore the laser gain rod has the advantages of low heat sink density and high cooling speed; and harm caused by various types of thermal effects can be effectively avoided.

Description

A kind of laser gain rod and there is its laser oscillator and laser amplifier

Technical field

The present invention relates to field of lasers, be specifically related to a kind of laser gain for pumping homogenize rod and there is its laser oscillator and laser amplifier.

Background technology

All solid state laser has that volume is little, lightweight, efficiency is high, stable performance, good reliability, life-span are long, easy to operate, nimble, the easy intellectuality that operates, the advantage such as pollution-free, played important effect in fields such as industrial processes, information transmission, remote sensings, the market demand is very huge.

Classify by operation material shape, all solid state laser is often divided into following several: bar-shaped laser, slab laser, disk laser and fiber laser etc.They respectively have advantage, all to attract the sight of numerous researchers in recent years, and all obtain and develop rapidly.But under high pump power, this several operation material shows some limitation, wherein, bar-shaped laser due to thermal effect serious, beam quality can be caused to worsen and fevering sodium effect; Although slab laser and disk laser have good radiating effect, often adopt high doping content to improve pump absorption efficiency, this can cause concentration quenching and upper energy level transition, and infringement pump light is to the conversion efficiency of laser; Fiber laser is owing to having very large area of dissipation, low doping content and tiny core size, at running hours, can output high-power, high light beam quality laser, but, when pulsed operation, high fibre core power density often causes fiber nonlinear effect, causes the damage of optical fiber.

Photonic crystal fiber has large mould field size, effectively can suppress fiber nonlinear effect, and meanwhile, fibre core weak leads the propagation that effect only allows fundamental transverse mode, is thus particularly suitable for high power, the laser oscillator of high light beam quality and laser amplifier.2009, the photonic crystal fiber of the fibre core 40 microns that the Mobius company of the U.S. produces based on the NKT of Denmark, was proposed the pulsed ultraviolet laser of 10W level.But due to optical fiber structure and the low rate of finished products of complexity, holding at high price of photonic crystal fiber, has even accounted for more than 50% of whole laser cost, at present, only may be used for scientific research, greatly differ from each other from the application of large-scale market.

Laser bar has large cross sectional dimensions, can effectively suppress various nonlinear effect, simultaneously, laser bar also has large surface-to-volume ratio, is conducive to heat radiation, can avoid the various harm caused due to thermal effect, thus, high-power laser oscillator and laser amplifier is specially adapted to.But, in order to the convenience of processing and manufacturing, often the cross section of laser bar is designed to the shape that circle, octagon etc. have rotational symmetry, after causing pump light to propagate a segment distance in this laser bar, usually spatially present the cored screw shape distribution that weak edge, center is strong, this is also referred to as the skin effect of laser bar.

Divide according to propagation path, the pump light propagated in laser bar can be divided into meridional ray and oblique ray.So-called meridional ray be exactly those in laser bar in twice total reflection by the light of laser bar central shaft, and oblique ray to be exactly some and laser bar central shaft both not parallel, also disjoint light.These two kinds of light have different character in laser bar transmitting procedure.

For the laser bar with rotational symmetry, be meridian plane by any plane of central shaft, and the light being positioned at meridian plane is exactly meridional ray.According to the reflection law of light, meridian will be positioned at a meridian plane all the time, thus can carry out in meridional plane the research of meridional ray.As shown in Figure 1, assuming that in certain meridian plane, light incides laser bar facets with incidence angle θ and is injected in laser bar again.In laser bar, the angle of this incident ray and axis is α ₀, then have at incident end face place:

n ₀sinθ=n ₁sinα ₀(1.1)

Above formula is describe the Snell's law that light reflects behavior on two medium cross-section, and the refractive index wherein in air is n ₀, the refractive index of laser bar is n ₁, and be uniform everywhere.If want light to be constrained on propagate in laser bar and be unlikely to reflect away from the side of laser bar, then must meet the total reflection condition in laser bar side, namely

$\sin \mathrm{\α}=\cos {\mathrm{\α}}_0\≥\frac{n_2}{n_1}---\left(1.2\right)$

Above formula is substituted into formula (1.1), just obtains the propagation conditions of incident meridional ray:

In above formula, when equal sign is set up, corresponding incidence angle is called maximum incident angle, with θ _maxrepresent.That is only at laser bar facets incidence angle θ≤θ _maxlight could propagate in laser bar.For laser bar, this possible maximum incidence angle is called the acceptance angle of laser bar, and only with n ₁, n ₂relevant.Traditionally, the sine value of acceptance angle is defined as the numerical aperture of laser bar, represents with N.A.

$N.A.=\sin {\mathrm{\θ}}_{\max }=\sqrt{n_1^2-n_2^2}---\left(1.4\right)$

Incide the light beam of laser bar facets except meridional ray, also have a lot of oblique ray.It is both not parallel that oblique ray is exactly some and central shaft, also disjoint light.They and central shaft are different surface beelines, so must carry out with vector method in three dimensions for the discussion of oblique ray.Because oblique ray and central shaft be not in a plane, oblique ray carries out a total reflection in laser bar, and the orientation of plane will change once, and its light path track is the spiral broken line in space.

As shown in Figure 2, direction vector is S ₀=L ₀i+M ₀j+N ₀the light of k is to the position P of laser bar facets ₀=x ₀i+y ₀j(i, j, k are unit vector).If α _mrepresent the radial vector of m secondary reflection point, and S _mfor the radiation direction vector before immediately m secondary reflection, have according to the condition that light before and after reflection is coplanar:

(S _m-S _m+1)α _m=0 (1.5)

The condition equaling angle of reflection by incidence angle again has

(S _m+S _m+1)α _m=0 (1.6)

In addition, condition total reflection occurring in laser bar side is

$S_m\frac{{\mathrm{\α}}_m}{\left|{\mathrm{\α}}_m\right|}\≤\frac{\sqrt{n_1^2-n_2^2}}{n_1}---\left(1.7\right)$

Can propagate in laser bar at which type of oblique ray of laser bar incidence end to study, we are by S ₀and P ₀substitution formula (1.7), can obtain

$n_1\frac{L_{0}x+M_{0}y}{\sqrt{x_0^2+y_0^2}}\≤\sqrt{n_1^2-n_2^2}---\left(1.8\right)$

In other words, meet the incident ray of above formula, oblique ray can be become and transmit in laser bar.

If incident ray is at x ₀=a, y ₀=0 place is incident, then

n ₁L ₀≤N.A.

This represents incident ray and M ₀irrelevant.Therefore, when pump light injects laser bar with the larger angle of divergence, L ₀be worth very little, then light will almost be locked near laser bar side, i.e. the total reflection that repeats in the side of laser bar of light, entirety is advanced in a spiral manner, and the light of central area is more weak, presents the spatial distribution that weak edge, center is strong, as shown in Figure 3.

Summary of the invention

The present invention one of is intended to solve the problems of the technologies described above at least to a certain extent or at least provides a kind of useful business to select.

The object of the invention is to propose that a kind of skin effect is little, the more uniform laser gain rod of pump light spatial distribution.

According to a kind of laser gain rod of the embodiment of the present invention, the cross section of described laser gain rod is rotation asymmetry, side and the section of laser gain rod described in it have all carried out polishing, wherein, be injected into the pump light in described laser gain rod, in communication process, be not easy the helical space distribution that weak edge, formation center is strong, contribute to improving the skin effect of described pump light in described laser gain rod, make described pump light spatial distribution in described laser gain rod more even.

In one embodiment of the invention, the material of described laser gain rod is be mixed with the laser crystal of thulium, laser glass, laser ceramics or laser plastic.

In one embodiment of the invention, described thulium comprises one or more the combination in neodymium (Nd), ytterbium (Yb), erbium (Er), thulium (Tm), holmium (Ho).

In one embodiment of the invention, described laser crystal comprises yag crystal (YAG), yttrium vanadate crystal (YVO ₄), gadolinium vanadate crystal (GdVO ₄), one or more combination in lithium yttrium fluoride (YLF).

In one embodiment of the invention, the external diameter of described laser gain rod is 0.05-20mm.

In one embodiment of the invention, the shape of cross section of described laser gain rod is D shape or inequilateral polygon etc.

Another object of the present invention is to propose the laser oscillator that a kind of efficiency is high, loss is few.

According to the laser oscillator of the embodiment of the present invention, there is the above-mentioned laser gain rod of the present invention.

Another object of the present invention is to propose the laser amplifier that a kind of efficiency is high, loss is few.

According to the laser amplifier of the embodiment of the present invention, there is the above-mentioned laser gain rod of the present invention.

The present invention compared with prior art, at least tool has the following advantages: (1) pump light is behind the side or end face injection of laser gain rod, total reflection is there is in the side of laser gain rod, thus be constrained in laser gain rod always and propagate, simultaneously, due to the rotation asymmetry of side, pump light is not easy to form hollow spiral light, thus more even in spatial distribution.(2) rod of the laser gain for pumping homogenize of the present invention also has low doping content and large cooling surface area, and thus, heat sink density is low, and radiating rate is fast, effectively can avoid the harm caused by various thermal effect.

Additional aspect of the present invention and advantage will part provide in the following description, and part will become obvious from the following description, or be recognized by practice of the present invention.

Accompanying drawing explanation

Above-mentioned and/or additional aspect of the present invention and advantage will become obvious and easy understand from accompanying drawing below combining to the description of embodiment, wherein:

Fig. 1 is the schematic diagram of the propagation of meridional ray in laser bar

Fig. 2 is another schematic diagram of the propagation of meridional ray in laser bar

Fig. 3 is the schematic diagram of the generation of circular laser bar inside spin light

Fig. 4 is the pump distribution figure in traditional circle, octagon, hexagonal laser gain rod

Fig. 5 is structural representation and the pump distribution figure of the laser gain rod for pumping homogenize provided by the invention.

Embodiment

Be described below in detail embodiments of the invention, the example of described embodiment is shown in the drawings, and wherein same or similar label represents same or similar element or has element that is identical or similar functions from start to finish.Be exemplary below by the embodiment be described with reference to the drawings, be intended to for explaining the present invention, and can not limitation of the present invention be interpreted as.

In describing the invention, it will be appreciated that, term " " center ", " longitudinal direction ", " transverse direction ", " length ", " width ", " thickness ", " on ", D score, " front ", " afterwards ", " left side ", " right side ", " vertically ", " level ", " top ", " end " " interior ", " outward ", " clockwise ", orientation or the position relationship of the instruction such as " counterclockwise " are based on orientation shown in the drawings or position relationship, only the present invention for convenience of description and simplified characterization, instead of indicate or imply that the device of indication or element must have specific orientation, with specific azimuth configuration and operation, therefore limitation of the present invention can not be interpreted as.

In addition, term " first ", " second " only for describing object, and can not be interpreted as instruction or hint relative importance or imply the quantity indicating indicated technical characteristic.Thus, be limited with " first ", the feature of " second " can express or impliedly comprise one or more these features.In describing the invention, the implication of " multiple " is two or more, unless otherwise expressly limited specifically.

In the present invention, unless otherwise clearly defined and limited, the term such as term " installation ", " being connected ", " connection ", " fixing " should be interpreted broadly, and such as, can be fixedly connected with, also can be removably connect, or connect integratedly; Can be mechanical connection, also can be electrical connection; Can be directly be connected, also indirectly can be connected by intermediary, can be the connection of two element internals.For the ordinary skill in the art, above-mentioned term concrete meaning in the present invention can be understood as the case may be.

In the present invention, unless otherwise clearly defined and limited, fisrt feature second feature it " on " or D score can comprise the first and second features and directly contact, also can comprise the first and second features and not be directly contact but by the other characterisation contact between them.And, fisrt feature second feature " on ", " top " and " above " comprise fisrt feature directly over second feature and oblique upper, or only represent that fisrt feature level height is higher than second feature.Fisrt feature second feature " under ", " below " and " below " comprise fisrt feature immediately below second feature and tiltedly below, or only represent that fisrt feature level height is less than second feature.

The object of the invention is to propose that a kind of skin effect is little, the more uniform laser gain rod of pump light spatial distribution.

According to a kind of laser gain rod of the embodiment of the present invention, the cross section of described laser gain rod is rotation asymmetry, side and the section of laser gain rod described in it have all carried out polishing, wherein, be injected into the pump light in described laser gain rod, in communication process, be not easy the helical space distribution that weak edge, formation center is strong, contribute to improving the skin effect of described pump light in described laser gain rod, make described pump light spatial distribution in described laser gain rod more even.

In one embodiment of the invention, the material of described laser gain rod is be mixed with the laser crystal of thulium, laser glass, laser ceramics or laser plastic.

In one embodiment of the invention, described thulium comprises one or more the combination in neodymium (Nd), ytterbium (Yb), erbium (Er), thulium (Tm), holmium (Ho).

In one embodiment of the invention, described laser crystal comprises yag crystal (YAG), yttrium vanadate crystal (YVO ₄), gadolinium vanadate crystal (GdVO ₄), one or more combination in lithium yttrium fluoride (YLF).

In one embodiment of the invention, the external diameter of described laser gain rod is 0.05-20mm.

In one embodiment of the invention, the shape of cross section of described laser gain rod is D shape or inequilateral polygon etc.

Another object of the present invention is to propose the laser oscillator that a kind of efficiency is high, loss is few.

According to the laser oscillator of the embodiment of the present invention, there is the above-mentioned laser gain rod of the present invention.

Another object of the present invention is to propose the laser amplifier that a kind of efficiency is high, loss is few.

According to the laser amplifier of the embodiment of the present invention, there is the above-mentioned laser gain rod of the present invention.

For making those skilled in the art understand the present invention better, existing composition graphs 4-Fig. 5 is further elaborated.

Fig. 4 (a-c) represents that existing cross section is the pump light distribution in the circle of Rotational Symmetry figure, octagon and hexagon laser gain rod respectively.Assuming that the material of laser gain rod is Nd:YAG crystal (refractive index is 1.823), the radius of cross section is 0.5mm, and length is 50mm, pump light is area source, and diameter is 0.4mm, and numerical aperture equals 0.3, wavelength is 808nm, and gross power is 1W, and the one end getting close to laser gain rod is placed.Pump light distribution on the booster (rod) cross section at selected distance light source 30mm place is as result during pump light stable transfer.From the simulation result of Fig. 4, for circle, octagon and hexagonal laser bar, after pump light transmits a segment distance wherein, the spiral Light distribation of hollow can be formed gradually, this is obviously unfavorable for the pattern matching of pump light and laser, limits the conversion efficiency of pump light to laser.

Fig. 5 (a) represents the light transmition example in a kind of D type transverse cross section laser gain rod.The cross section of D shape destroys the rotational symmetry of laser bar significantly, thus, in the transmitting procedure of light, cannot form the spiral light being close to laser bar side, more be conducive to realizing being uniformly distributed of pump light.Fig. 5 (b) is depicted as the simulation result of D shape laser gain rod inside-pumping distribution.The radius b getting circular portion in laser bar is the bond length a of 0.5mm, D shape part is 0.25mm, and the length of laser bar is 50mm; Pump light is area source, and diameter is 0.4mm, and numerical aperture equals 0.3, and wavelength is 808nm, and gross power is 1W, and the one end getting close to booster (rod) is equally placed.Pump light distribution on the booster (rod) cross section at same selected distance light source 30mm place is as result during pump light stable transfer.From simulation result, in the laser bar of D shape cross section, pump light is more easily spatially formed and distributes comparatively uniformly, is thus conducive to the pattern matching realizing pump light and laser, contributes to promoting the conversion efficiency of pump light to laser.Similarly, in the laser gain rod of other inequilateral polygonal crosssection, be not easy equally to form spiral light, be therefore conducive to the raising with conversion efficiency that is uniformly distributed realizing pump light.

The present invention compared with prior art, at least tool has the following advantages: (1) pump light is behind the side or end face injection of laser gain rod, total reflection is there is in the side of laser gain rod, thus be constrained in laser gain rod always and propagate, simultaneously, due to the rotation asymmetry of side, pump light is not easy to form hollow spiral light, thus more even in spatial distribution.(2) rod of the laser gain for pumping homogenize of the present invention also has low doping content and large cooling surface area, and thus, heat sink density is low, and radiating rate is fast, effectively can avoid the harm caused by various thermal effect.

In the description of this specification, specific features, structure, material or feature that the description of reference term " embodiment ", " some embodiments ", " example ", " concrete example " or " some examples " etc. means to describe in conjunction with this embodiment or example are contained at least one embodiment of the present invention or example.In this manual, identical embodiment or example are not necessarily referred to the schematic representation of above-mentioned term.And the specific features of description, structure, material or feature can combine in an appropriate manner in any one or more embodiment or example.

Although illustrate and describe embodiments of the invention above, be understandable that, above-described embodiment is exemplary, can not be interpreted as limitation of the present invention, those of ordinary skill in the art can change above-described embodiment within the scope of the invention when not departing from principle of the present invention and aim, revising, replacing and modification.

Claims (8)

1. a laser gain rod, it is characterized in that, the shape of cross section of described laser gain rod is D type cross section or the inequilateral polygonal crosssection of rotation asymmetry, side and the end face of described laser gain rod have all carried out polishing, pump light injects from the side of laser gain rod or end face, total reflection is there is in the side of described laser gain rod, wherein, be injected into the pump light in described laser gain rod, the helical space distribution that weak edge, formation center is strong is not easy in communication process, contribute to improving the skin effect of described pump light in described laser gain rod, make described pump light spatial distribution in described laser gain rod more even.

2. laser gain rod as claimed in claim 1, is characterized in that, the material of described laser gain rod is be mixed with the laser crystal of thulium, laser glass, laser ceramics or laser plastic.

3. laser gain rod as claimed in claim 2, it is characterized in that, described thulium comprises one or more the combination in neodymium, ytterbium, erbium, thulium, holmium.

4. laser gain rod as claimed in claim 2, it is characterized in that, described laser crystal comprises one or more the combination in yag crystal, yttrium vanadate crystal, gadolinium vanadate crystal, lithium yttrium fluoride.

5. laser gain rod as claimed in claim 1, it is characterized in that, the external diameter of described laser gain rod is 0.05-20mm.

6. laser gain rod as claimed in claim 1, it is characterized in that, the shape of cross section of described laser gain rod is D shape or inequilateral polygon.

7. a laser oscillator, is characterized in that, has the laser gain rod described in any one of claim 1-5.

8. a laser amplifier, is characterized in that, has the laser gain rod described in any one of claim 1-5.