阅读说明：本技术 一种多光束泵浦的光参量振荡器装置 (Optical parametric oscillator device of multi-beam pump ) 是由 尹志军 吴冰 张虞 许志城 于 2019-12-19 设计创作，主要内容包括：本申请提供一种多光束泵浦的光参量振荡器装置,包括：泵浦激光器、第一光分束器装置、及光参量振荡器；所述泵浦激光器输出泵浦光,射入所述第一光分束器装置；所述第一光分束器装置包括第一折射光学元件和第二折射光学元件；经由所述泵浦激光器输出的泵浦光射入所述第一折射光学元件进行角度分束,输出发散角不同的多束激光；所述发散角不同的多束激光射入所述第二折射光学元件进行偏折,输出平行的多束激光；所述平行的多束激光射入所述光参量振荡器振荡,输出所述多波长激光。该装置的用于光分束的结构具有零部件少,结构简单紧凑,可靠性高的优点,从而用以解决上述现有技术中光分束结构零部件多,结构复杂,可靠性低的问题。(The application provides an optical parametric oscillator device of multiple beam pumping, includes: a pump laser, a first optical beam splitter device, and an optical parametric oscillator; the pump laser outputs pump light which is emitted into the first optical beam splitter device; the first optical splitter device includes a first refractive optical element and a second refractive optical element; the pump light output by the pump laser enters the first refractive optical element for angular beam splitting, and a plurality of laser beams with different divergence angles are output; the multiple laser beams with different divergence angles enter the second refraction optical element to be deflected, and parallel laser beams are output; and the parallel multiple laser beams enter the optical parametric oscillator to oscillate, and the multi-wavelength laser is output. The structure for light beam splitting of the device has the advantages of few parts, simple and compact structure and high reliability, thereby solving the problems of more parts, complex structure and low reliability of the light beam splitting structure in the prior art.)

1. A multi-beam pumped optical parametric oscillator device, comprising: a pump laser, a first optical beam splitter device, and an optical parametric oscillator;

the pump laser outputs pump light which is emitted into the first optical beam splitter device; the first optical beam splitter device splits the incident pump light and outputs a plurality of beams of light; the optical parametric oscillator receives the multiple beams of light to oscillate and outputs multi-wavelength laser;

it is characterized in that the preparation method is characterized in that,

the first optical splitter device includes a first refractive optical element and a second refractive optical element;

the pump light output by the pump laser enters the first refractive optical element for angular beam splitting, and a plurality of laser beams with different divergence angles are output;

the multiple laser beams with different divergence angles enter the second refraction optical element to be deflected, and parallel laser beams are output;

the parallel multiple lasers are injected into the optical parametric oscillator to oscillate and output the multi-wavelength laser;

said first beam splitter means comprising an optically transparent dielectric body;

the first surface of the optical transparent medium body forms the first refractive optical element, and the second surface of the optical transparent medium body, which is arranged opposite to the first surface, forms the second refractive optical element.

2. The multi-beam pumped optical parametric oscillator device of claim 1,

the first surface is provided with a grating structure, and the grating structure comprises rectangular convex parts and rectangular concave parts which are arranged at intervals;

the grating structure forms the first refractive optical element.

3. The multi-beam pumped optical parametric oscillator device of claim 2,

diffraction efficiency of the convex grating formed by the rectangular convex part

where m is the order of diffraction and phi is the phase of the modulation.

4. The multi-beam pumped optical parametric oscillator device of claim 3,

the phase phi is given by the following equation:

wherein the content of the first and second substances,

5. The multi-beam pumped optical parametric oscillator device of claim 4,

the diffraction angle θ is given by the following equation:

wherein the content of the first and second substances,

6. The multi-beam pumped optical parametric oscillator device of claim 1,

the second surface is provided with a plurality of refraction intervals, so that a plurality of laser beams with different divergence angles are refracted through the corresponding refraction intervals respectively to form parallel light beams for outputting.

7. The multi-beam pumped optical parametric oscillator device of claim 6,

the refraction interval comprises a plane interval, an upper side refraction interval and a lower side refraction interval;

the plane section is positioned at the center and the periphery of the second surface, so that the laser beam vertical to the second surface is horizontally output through the plane section;

the upside refracts the interval and is located the interval top in plane, the interval is located in the interval below in plane in downside refracts the interval to with the laser beam that the second surface becomes suitable incident angle, via respectively corresponding the interval with the interval horizontal output of downside refracts the upside refracts.

8. The multi-beam pumped optical parametric oscillator device of claim 7,

the upside refracts the interval with the downside refracts the interval and all is equipped with toper bellying and the toper depressed part that the interval set up.

9. The multi-beam pumped optical parametric oscillator device of any one of claims 1 to 8,

the optical parametric oscillator device also comprises an optical shaping device, wherein the optical shaping device comprises a first shaping lens and a second shaping lens which are arranged in parallel;

the pump light emitted by the pump laser is converged by the first shaping lens;

the pump light converged by the first shaping lens is collimated by the second shaping lens.

10. The multi-beam pumped optical parametric oscillator device of any one of claims 1 to 8,

the optical parametric oscillator comprises a front cavity mirror, a multi-channel superlattice and a rear cavity mirror;

the front cavity mirror and the rear cavity mirror are arranged in parallel and are vertical to the incident beam;

the front cavity mirror and the rear cavity mirror are highly transparent to light within a first preset range and highly reflective to light within a second preset range.

11. The multi-beam pumped optical parametric oscillator device of claim 10,

the multi-channel superlattice comprises a plurality of lattice channels with the same number as that of incident light beams, so that each incident light beam is respectively input into one corresponding lattice channel.

12. The multi-beam pumped optical parametric oscillator device of any one of claims 1 to 8,

the optical parametric oscillator device further comprises a second optical beam splitter device;

the second beam splitter device comprises a third refractive optical element and a fourth refractive optical element;

the multi-wavelength laser output by the optical parametric oscillator is incident on the third refractive optical element for angular beam splitting, and a plurality of laser beams with different divergence angles are output;

a plurality of laser beams having different divergence angles and output from the third refractive optical element are incident on the fourth refractive optical element and deflected, and a plurality of parallel laser beams are output.

13. The multi-beam pumped optical parametric oscillator device of claim 12,

the optical parametric oscillator device further comprises a third shaping lens;

and the parallel light beams output by the fourth refractive optical element are collimated by the third shaping lens and then output.

Technical Field

The present application relates to the field of laser technology, and more particularly, to an optical parametric oscillator device with multiple beam pumping.

Background

An Optical Parametric Oscillator (English: Optical Parametric Oscillator) is a Parametric Oscillator that oscillates at an Optical frequency. It will input a frequency of

Is converted into two output lights (signal lights) of lower frequency by second-order nonlinear optical interaction

And an idler) The sum of the frequencies of the two output lights is equal to the input light frequency:

. For historical reasons, the two output lights are referred to as "signal light" and "idler light", which output light at a higher frequency is referred to as "signal light".

An optical superlattice is a nonlinear optical crystal with an artificial microstructure, and the basic theoretical basis is quasi-phase matching. The quasi-phase matching theory is proposed by Blemebergen in 1962, and compensates the wave vector mismatch between fundamental waves and harmonic waves caused by dispersion in the nonlinear parameter process by periodically modulating the nonlinear polarizability of the crystal, so as to obtain the effective enhancement of the nonlinear optical effect. Quasi-phase matching can only be accomplished in materials with modulated structures, often referred to as optical superlattices, since the characteristic length or period of such modulation is in the order of microns, much larger than the lattice constant of the crystal. The structural design of the optical superlattice is crucial to the performance of the optical superlattice in a nonlinear optical process, and the structural design of the optical superlattice goes through a plurality of stages such as period, quasi-period and non-period. The quasi-periodic superlattice has multiple groups of inverse lattice vectors and can efficiently complete multiple optical parametric processes at the same time. The periodic structure of the optical superlattice material may also be designed as a two-dimensional structure, such as a sector, a lattice, multiple channels, etc., which may produce different wavelength outputs when pump light is incident on different periodic structures.

Optical superlattice materials are ferroelectric crystals and typically include lithium niobate (LiNbO 3, LN), lithium tantalate (LiTaO 3, LT), and potassium titanyl phosphate (KTiOPO 4, KTP), among others. These ferroelectric crystals have high nonlinear coefficient, and have the advantages of no walk-off, high efficiency, tunable wavelength and the like after the quasi-phase matching technology, so that the ferroelectric crystals are widely used in optical parametric oscillators. However, these materials have a low laser damage threshold, typically only a few hundred megawatts per square centimeter (MW/cm 2), so the input pump light cannot be too strong, which would cause crystal damage. In order to output higher power, an incident light spot needs to be enlarged, so that the power density under the same power is reduced, an oval light spot is adopted to pump a superlattice in the prior art, the oval or elongated light spot enables the transverse length of an original round light spot with the diameter less than 1mm to be increased by multiple times, and the total output power is improved. However, such a long stripe-shaped light spot causes a large thermal lens effect inside the crystal, which causes deformation and distortion of the light spot, and the conversion efficiency is severely reduced when operating at high power. For example, when the conversion efficiency of circular beam pumping is 20%, the total power of the circular beam pumping should theoretically be increased by 10 times when the beam area is increased to 10 times by increasing the beam diameter; in practice, however, the conversion efficiency is reduced due to the thermal lens effect, and the conversion efficiency may be only 5%, and the effect of the co-power boost is greatly reduced.

In another prior art, the output power is increased by splitting a circular beam and pumping the beam with multiple lasers to distribute the total power among the multiple beams. Two beams of laser are divided into four beams of laser through a semi-transparent semi-reflecting mirror and a plurality of lenses to be incident into a superlattice crystal, and high-power mid-infrared laser output of multi-beam pumping is achieved. In the other type, a beam splitter is formed by a plurality of semi-transparent semi-reflecting mirrors and prisms, 532nm laser output by a solid laser is divided into six beams, and the effect of multi-wavelength output is realized by the change of incident angles on nonlinearity. And the other method is to pump OPO by a two-wavelength or even three-wavelength pump source and obtain multi-wavelength laser output by the change of the pump wavelength.

The main problems of the above-mentioned schemes are that the multi-beam light splitting device has a complex structure, the whole system has a large volume, and the reliability of the whole system is reduced due to a plurality of optical elements. For example, the above-mentioned one prior art adopts two laser pumping sources, four lenses, eight reflectors, and three corner prisms to implement a light splitting device; another prior art uses two prisms, nine mirrors, and other optical elements to implement a beam splitting device. The distribution postures of the optical elements on the space can be deformed along with the increase of the service time, and can also be deformed along with the heat effect, so that the accuracy of the whole optical path and the stability of laser output can generate images, and the volume and the weight of the optical elements are difficult to reduce.

Binary optics is a new optical branch developed based on the light wave diffraction theory, and is a leading-edge subject formed by mutual penetration and intersection of optics and microelectronic technologies. The planar relief type binary optical device manufactured based on the computer aided design and the micron-scale processing technology has the characteristics of light weight, easiness in copying, low manufacturing cost and the like, and can realize new functions of tiny, array, integration, arbitrary wave surface transformation and the like which are difficult to finish by the traditional optics, so that the optical engineering and the optical technology show unprecedented important functions and wide application prospects in various fields of modern national defense science and technology and industry such as space technology, laser processing, computing technology and information processing, optical fiber communication, biomedicine and the like. With the rapid development of modern optical and optoelectronic technologies, optoelectronic instruments and their components have been subject to profound and enormous changes. Optical components have not been just refractive lenses, prisms, and mirrors. New optical elements such as microlens arrays, holographic lenses, diffractive optical elements, and gradient index lenses are also increasingly used in various optoelectronic instruments, making the optoelectronic instruments and their parts more compact, arrayed, and integrated. The micro-optical element is a key element for manufacturing a small-sized photoelectronic system, has the advantages of small volume, light weight, low cost and the like, and can realize new functions of micro, array, integration, imaging, wave surface conversion and the like which are difficult to realize by common optical elements.

Disclosure of Invention

Based on the above introduction, the present application provides an optical parametric oscillator device of multiple beam pumps, and the structure of the device for optical beam splitting has the advantages of few components, simple and compact structure, and high reliability, so as to solve the above-mentioned problems of many components, complex structure, and low reliability of the optical beam splitting structure in the prior art.

In order to solve the above technical problem, the present application provides an optical parametric oscillator device for multi-beam pumping, comprising: a pump laser, a first optical beam splitter device, and an optical parametric oscillator;

the pump laser outputs pump light which is emitted into the first optical beam splitter device; the first optical beam splitter device splits the incident pump light and outputs a plurality of beams of light; the optical parametric oscillator receives the multiple beams of light to oscillate and outputs multi-wavelength laser;

the first optical splitter device includes a first refractive optical element and a second refractive optical element;

the pump light output by the pump laser enters the first refractive optical element for angular beam splitting, and a plurality of laser beams with different divergence angles are output;

the multiple laser beams with different divergence angles enter the second refraction optical element to be deflected, and parallel laser beams are output;

and the parallel multiple laser beams enter the optical parametric oscillator to oscillate, and the multi-wavelength laser is output.

Alternatively to this, the first and second parts may,

said first beam splitter means comprising an optically transparent dielectric body;

the first surface of the optical transparent medium body forms the first refractive optical element, and the second surface of the optical transparent medium body, which is arranged opposite to the first surface, forms the second refractive optical element.

Alternatively to this, the first and second parts may,

the first surface is provided with a grating structure, and the grating structure comprises rectangular convex parts and rectangular concave parts which are arranged at intervals;

the grating structure forms the first refractive optical element.

Alternatively to this, the first and second parts may,

diffraction efficiency of the convex grating formed by the rectangular convex part

The following equation gives:

wherein m is the order of diffraction,

is the adjusted phase.

Alternatively to this, the first and second parts may,

phase of electricity

The following equation gives:

wherein the content of the first and second substances,

the wavelength of the incident laser is 1, the refractive index of air is 1, and the refractive index of the light transparent medium body is n.

Alternatively to this, the first and second parts may,

the diffraction angle θ is given by the following equation:

wherein the content of the first and second substances,

m is the order of diffraction for the incident laser wavelength.

Alternatively to this, the first and second parts may,

the second surface is provided with a plurality of refraction intervals, so that a plurality of laser beams with different divergence angles are refracted through the corresponding refraction intervals respectively to form parallel light beams for outputting.

Alternatively to this, the first and second parts may,

the refraction interval comprises a plane interval, an upper side refraction interval and a lower side refraction interval;

the plane section is positioned at the center and the periphery of the second surface, so that the laser beam vertical to the second surface is horizontally output through the plane section;

the upside refracts the interval and is located the interval top in plane, the interval is located in the interval below in plane in downside refracts the interval to with the laser beam that the second surface becomes suitable incident angle, via respectively corresponding the interval with the interval horizontal output of downside refracts the upside refracts.

Alternatively to this, the first and second parts may,

the upside refracts the interval with the downside refracts the interval and all is equipped with toper bellying and the toper depressed part that the interval set up.

Alternatively to this, the first and second parts may,

the optical parametric oscillator device also comprises an optical shaping device, wherein the optical shaping device comprises a first shaping lens and a second shaping lens which are arranged in parallel;

the pump light emitted by the pump laser is converged by the first shaping lens;

the pump light converged by the first shaping lens is collimated by the second shaping lens.

Alternatively to this, the first and second parts may,

the optical parametric oscillator comprises a front cavity mirror, a multi-channel superlattice and a rear cavity mirror;

the front cavity mirror and the rear cavity mirror are arranged in parallel and are vertical to the incident beam;

the front cavity mirror and the rear cavity mirror are highly transparent to light within a first preset range and highly reflective to light within a second preset range.

Alternatively to this, the first and second parts may,

the multi-channel superlattice comprises a plurality of lattice channels with the same number as that of incident light beams, so that each incident light beam is respectively input into one corresponding lattice channel.

Alternatively to this, the first and second parts may,

the optical parametric oscillator device further comprises a second optical beam splitter device;

the second beam splitter device comprises a third refractive optical element and a fourth refractive optical element;

the multi-wavelength laser output by the optical parametric oscillator is incident on the third refractive optical element for angular beam splitting, and a plurality of laser beams with different divergence angles are output;

a plurality of laser beams having different divergence angles and output from the third refractive optical element are incident on the fourth refractive optical element and deflected, and a plurality of parallel laser beams are output.

Alternatively to this, the first and second parts may,

the optical parametric oscillator device further comprises a third shaping lens;

and the parallel light beams output by the fourth refractive optical element are collimated by the third shaping lens and then output.

The application provides an optical parametric oscillator device comprising: a pump laser, a first optical beam splitter device, and an optical parametric oscillator; the pump laser outputs pump light which is emitted into the first optical beam splitter device; the first optical beam splitter device splits the incident pump light and outputs a plurality of beams of light; the optical parametric oscillator receives the multiple beams of light to oscillate and outputs multi-wavelength laser; the first optical splitter device includes a first refractive optical element and a second refractive optical element; the pump light output by the pump laser enters the first refractive optical element for angular beam splitting, and a plurality of laser beams with different divergence angles are output; the multiple laser beams with different divergence angles enter the second refraction optical element to be deflected, and parallel laser beams are output; and the parallel multiple laser beams enter the optical parametric oscillator to oscillate, and the multi-wavelength laser is output.

In the above structural design, the present application provides a light splitting structure, that is, a first light splitter device, including a first refractive optical element and a second refractive optical element; the pump light output by the pump laser enters the first refractive optical element for angular beam splitting, and a plurality of laser beams with different divergence angles are output; the multiple laser beams with different divergence angles enter the second refraction optical element to be deflected, and parallel laser beams are output; and the parallel multiple laser beams enter the optical parametric oscillator to oscillate, and the multi-wavelength laser is output. It follows that the light is split by two components. Compared with the structure design of adopting a plurality of prisms and reflectors in the prior art, the structure is greatly simplified, and meanwhile, the reliability is obviously improved.

Drawings

FIG. 1 is a functional block diagram of a multiple beam pumped optical parametric oscillator device in an exemplary embodiment of the present application;

FIG. 2 is a functional block diagram of a first optical splitter device in an exemplary embodiment of the present application;

FIG. 3 is a schematic diagram of a first optical beam splitter device in an exemplary embodiment of the present application;

FIG. 4 is a schematic diagram of light rays from a second refractive element of a first optical beam splitter device in an exemplary embodiment of the present application;

FIG. 5 is a schematic diagram of an optical parametric oscillator in an exemplary embodiment of the present application;

fig. 6 is a schematic diagram of a multi-beam pumped optical parametric oscillator device in an exemplary embodiment of the present application.

Wherein, the corresponding relation between the parts in the figure and the reference numbers is as follows:

a pump laser 1;

a first optical splitter device 2; a first refractive optical element 201; a rectangular boss 2011; a rectangular recessed portion; 2012; a second refractive optical element 202; a planar section 2021; an upper refractive zone 2022; a conical boss; 2022 a; a conical depression 2022 b; lower refractive zone 2023;

an optical parametric oscillator 3; a front cavity mirror 301; a rear cavity mirror 302; a multi-channel superlattice; 303; a lattice channel 3031;

a first shaping lens 401; a second shaping lens 402;

a second optical splitter device 5;

and a third shaping lens 6.

Detailed Description

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following examples do not represent all embodiments consistent with the present application. But merely as exemplifications of systems and methods consistent with certain aspects of the application, as recited in the claims.

As shown in fig. 1, 2 and 3, fig. 1 is a functional block diagram of a multi-beam pumped optical parametric oscillator device in an exemplary embodiment of the present application; FIG. 2 is a functional block diagram of a first optical splitter device in an exemplary embodiment of the present application; fig. 3 is a schematic structural diagram of a first optical splitter device in an exemplary embodiment of the present application.

As shown in fig. 1, in one embodiment of the present application, the optical parametric oscillator 3 device of the multi-beam pumping includes a pump laser 1, a first optical beam splitter device 2, and an optical parametric oscillator 3; the pump laser 1 outputs pump light, and the pump light is injected into the first optical beam splitter device 2; the first optical beam splitter device 2 splits the incident pump light and outputs a plurality of beams of light; the optical parametric oscillator 3 receives the plurality of beams of light to oscillate and outputs a multi-wavelength laser.

On the basis of the above-described structure, as shown in fig. 2 and 3, the first optical beam splitter device 2 includes a first refractive optical element 201 and a second refractive optical element 202; the pump light output from the pump laser 1 enters the first refractive optical element 201 to be split angularly, and a plurality of laser beams having different divergence angles are output; a plurality of laser beams with different divergence angles enter the second refraction optical element 202 to be deflected, and a plurality of parallel laser beams are output; the parallel plural laser beams are incident on the optical parametric oscillator 3 and oscillated, and a multi-wavelength laser is output.

Specifically, as shown in fig. 1, a pump laser 1 outputs a high-power pump light, the pump light is split by a first optical splitter device 2, the first optical splitter device may be a refractive binary optical element (ROE), the split pump light enters an optical parametric oscillator 3(OPO) for oscillation, and a multi-wavelength laser is output under an optical nonlinear effect.

Specifically, the pump laser 1 may be a solid laser, a gas laser, a fiber laser, a semiconductor laser, or the like. The spot output was in the shape of a circular single transverse mode (TEM 00). The laser beam is collimated to form an approximately parallel beam, and enters an ROE beam splitting. The ROE has the effect of splitting a beam of parallel incident laser light. The ROE consists of two ROE elements, wherein the first ROE carries out angle beam splitting on one laser beam and divides the laser beam into a plurality of laser beams with different divergence angles; the second ROE deflects these lasers with different divergence angles so that the output laser beams remain parallel to each other. Note that, in the present application, the first ROE is also referred to as a first refractive optical element 201, and the second ROE is also referred to as a second refractive optical element 202.

In the above structural design, the present application provides a light splitting structure, that is, the first optical splitter device 2, including a first refractive optical element 201 and a second refractive optical element 202; the pump light output from the pump laser 1 enters the first refractive optical element 201 to be split angularly, and a plurality of laser beams having different divergence angles are output; a plurality of laser beams with different divergence angles enter the second refraction optical element 202 to be deflected, and a plurality of parallel laser beams are output; the parallel plural laser beams are incident on the optical parametric oscillator 3 and oscillated, and a multi-wavelength laser is output. It follows that the light is split by two components. Compared with the structure design of adopting a plurality of prisms and reflectors in the prior art, the structure is greatly simplified, and meanwhile, the reliability is obviously improved.

In the above structural design, the structure of the first and second refractive optical elements 201 and 202 can be further explained. For example, as shown in FIGS. 2 and 3, the first beam splitter device 2 includes an optically transparent dielectric body; a first surface of the optically transparent dielectric body forms a first refractive optical element 201 and a second surface of the optically transparent dielectric body, which is arranged opposite the first surface, forms a second refractive optical element 202.

The structure design enables one optical medium body to realize the integrated design of two optical elements, thereby further reducing the number of parts, leading the structure to be more compact and leading the reliability to be higher.

Further, as shown in fig. 3, the first surface is provided with a grating structure, and the grating structure includes rectangular protrusions 2011 and rectangular recesses 2012 arranged at intervals; the grating structure forms a first refractive optical element 201.

As shown in fig. 3 in particular, the first refractive optical element 201 and the second refractive optical element 202 phase-modulate the outgoing light by changing the surface type or the refractive index in the body.

As shown in fig. 3, the first refractive optical element 201 and the second refractive optical element 202 modulate the phase of light by changing the surface topography, resulting in splitting and deflecting effects, generally a splitting effect into a plurality of parallel lights. The substrate material of the optically transparent dielectric body may be a variety of transparent media such as glass, polymer, or crystal. As shown in fig. 3, two ROE units are formed by changing the plane shapes of two parallel planes of a single optically transparent medium body, and two ROE effects can be achieved by using a single medium, that is, the first refractive optical element 201 and the second refractive optical element 202 of the present application are formed.

More specifically, the surface of the first refractive optical element 201 is constituted by a grating-type rectangular protrusion 2011 and a rectangular depression 2012, the grating period Λ of which is aligned in the beam splitting angle dispersion direction in the plane of the paper, and the relative height difference d between the rectangular protrusion 2011 and the rectangular depression 2012 determines the phase of the modulation

. When the refractive index of the substrate material is n, the phase is determined by the following formula:

wherein the wavelength of the incident laser isThe refractive index of air is 1. Diffraction angle according to the grating equation

Is determined by the following formula:

where m is the order of diffraction.

Diffraction efficiency of rectangular raised grating

Is determined by the following formula:

when in useWhen the diffraction efficiency reaches 81%, two beams of light splitting effects are formed. When in use

When the diffraction intensities of +1, 0 and-1 orders are the highest and equal, the diffraction efficiency of the third order is 87%, and a three-beam light splitting effect is formed. When the surface morphology is modulated into other configurations, similar or better effects can be obtained, and the specific design method can be calculated by adopting a Monte Carlo method or an annealing simulation algorithm.

In an embodiment of the present application, an exemplary description may also be made of the structure of the second refractive optical element 202. For example, as shown in fig. 3, the second surface is provided with a plurality of refraction sections, so that a plurality of laser beams with different divergence angles are refracted through the corresponding refraction sections to form parallel beam outputs.

Further, the refraction section includes a plane section 2021, an upper side refraction section 2022, and a lower side refraction section 2023; the plane section 2021 is located at the center and the periphery of the second surface, so that the laser beam perpendicular to the second surface is horizontally output through the plane section 2021.

The upper refraction section 2022 is located above the plane section 2021, and the lower refraction section 2023 is located below the plane section 2021, so that the laser beam having a proper incident angle with the second surface is horizontally outputted through the corresponding upper refraction section 2022 and lower refraction section 2023.

Further, as shown in fig. 3, the upper refraction section 2022 and the lower refraction section 2023 are provided with a conical convex portion 2022a and a conical concave portion 2022b which are arranged at intervals.

We can further explain the principle of the above structural design. Specifically, as shown in fig. 4, fig. 4 is a schematic diagram of light rays of the second refraction element of the first light splitting device in an exemplary embodiment of the present application.

Taking the three beam splitting as an example, the second refractive optical element 202 is designed to use a zone-division refraction method, so that lights with different incident angles are emitted in a parallel manner.

As shown in fig. 4, the two incident light beams are transmitted in the medium and respectively incident on the interface at different angles. The interface has a relative angle difference with the light beam according to the position of the light beam when the light beam is incidentWhen the beam is vertical to the surface of the medium, the direction of the emergent beam is not changed; when the angle of the incident beam is not perpendicular to the medium, the angle is deflected

Given according to snell's formula:

for example, when the angle between the interface and the horizontal is θ, the incident beam is inclined to the horizontal

In degrees, the medium refractive index n =1.5, and the angular relationship in fig. 4 has the following formula:

the transcendental equation above, two solutions are obtained:

degree and

and (4) degree. Thus, parallel beam emergence can be obtained with both angles. The light beam can be bent in a mode of covering a plane, and the structure mode of the light beam can also be similar to a Fresnel lens. The multiple planes shown for the second refractive optical element 202 cause it to bend.

In one embodiment of the present application, further exemplary description may be made of the structure of the optical parametric oscillator device. Specifically, as shown in fig. 5 and 6, fig. 5 is a schematic structural diagram of an optical parametric oscillator in an exemplary embodiment of the present application; fig. 6 is a schematic diagram of a multi-beam pumped optical parametric oscillator device in an exemplary embodiment of the present application.

As shown in fig. 6, the optical parametric oscillator 3 device further includes an optical shaping device, which includes two first shaping lenses 401 and a second shaping lens 402 arranged in parallel; the pump light emitted by the pump laser 1 is converged by the first shaping lens 401; the pump light condensed by the first shaping lens 401 is collimated by the second shaping lens 402.

As shown in fig. 5, the optical parametric oscillator 3 includes a front cavity mirror 301, a multi-channel superlattice 303, and a back cavity mirror 302;

the front cavity mirror 301 and the rear cavity mirror 302 are arranged in parallel and perpendicular to the incident light beam; the front cavity mirror 301 and the rear cavity mirror 302 are both highly transparent to light within a first preset range and highly reflective to light within a second preset range. The multi-channel superlattice 303 includes a plurality of lattice channels 3031 in an amount equal to the number of incident light beams, such that each incident light beam is input into a corresponding one of the lattice channels 3031.

As shown in fig. 6, the optical parametric oscillator 3 device further includes a second optical beam splitter device 5;

the second beam splitter device 5 comprises a third and a fourth refractive optical element; the multi-wavelength laser output from the optical parametric oscillator 3 is incident on a third refractive optical element to perform angular beam splitting, and a plurality of laser beams having different divergence angles are output; a plurality of laser beams having different divergence angles output from the third refractive optical element are incident on the fourth refractive optical element and deflected, and a plurality of parallel laser beams are output.

As shown in fig. 6, the optical parametric oscillator 3 device further includes a third shaping lens 6; the parallel light beams output by the fourth refractive optical element are collimated by the third shaping lens 6 and then output.

In the above structural design, we can further explain the working principle and working process.

Specifically, as shown in fig. 6, the pump light is coupled in by an optical fiber, and the pump laser 1 may be a solid, gas, optical fiber, or semiconductor laser. In the embodiment, a 1064nm optical fiber laser is used as a pumping source, the output power is 50W, the output pulse length is 100ns, and the repetition frequency is 100 KHz. The laser output by the pump laser 1 is guided into the device through the optical fiber and is diffused through the optical fiber ferrule fixed in the device.

As shown in fig. 6, the diverging pump light is beam-shaped by passing through two shaping lenses, i.e., a first shaping lens 401 and a second shaping lens 402. The first shaping lens 401 is a convex lens and converges laser light; the second shaping lens 402 is a concave lens, and collimates the converged laser light. The pump light forms a circular beam with a spot diameter of 1mm before entering the first ROE, also referred to herein as the first optical counter device. The first ROE is formed by quartz crystals, the front surface and the rear surface of the first ROE are provided with refractive index grating structures, the specific structure of the first ROE is designed through binary diffraction optics, and pumping light spots are divided into 5 beams of laser with equal power after passing through the first surface of the first ROE and are distributed in a fan shape on a plane; after passing through the second face of the ROE, the 5 fan-shaped diverging beams are shaped as 5 beams of light that are parallel to each other.

As shown in fig. 6, 5 parallel pump lights are incident into the optical parametric oscillator 3. The front cavity mirror 301 of the OPO (namely the optical parametric oscillator 3) is made of calcium fluoride material, and has high transmittance to 1064nm and high reflectance to 1400-2000 nm; the rear cavity mirror 302 of the OPO is highly transmissive to 1064nm and highly reflective to 1400-2000 nm. Another cavity mirror configuration is: the rear cavity mirror 302 of the OPO has high transmittance to 1064nm and has a reflectivity of 50-70% to 1400-2000 nm. The front cavity mirror 301 and the back cavity mirror 302 are placed in parallel, perpendicular to the incident beam. The multi-channel superlattice 303 is formed by Periodically Poled Lithium Niobate (PPLN), and has 5 lattice channels 3031, wherein each lattice channel 3031 has a width of 1mm, and the distance between the lattice channels 3031 is 1 mm. 5 beams of pump light are respectively incident from the 5 lattice channels 3031 and pass through the centers of the lattice channels 3031. The front end face and the rear end face of the PPLN are polished and coated with films, and the films are highly transparent to 1064nm and 1400nm-2000 nm. The polarization periods of the 5 lattice channels 3031 of PPLN are respectively: 31.5um, 31um, 30.5um, 30um and 29.5um, the mid infrared laser (idler) wavelength of outgoing is respectively at room temperature: 3020nm, 3271nm, 3472nm, 3665nm and 3839 nm. The polarization period may also have other values, covering the interval 2000nm-5000 nm. The temperature of the superlattice is controlled by a temperature control furnace, the temperature control range is from room temperature to 250 ℃, and the output wavelength can be adjusted by adjusting the temperature of the superlattice. The single beam power of 5 beams of pump light is 10W, the shape of the light spot is circular, the light beams are not affected with each other, and the high conversion efficiency is kept, which is about 15%. After OPO conversion, the average single beam output power is 1.5W, and the total output power is 7.5W.

The optical beam output from the OPO is split into parallel beams by another ROE (also referred to herein as a second beam splitter device 5). The diameter of the mid-infrared laser emitted by the OPO is similar to that of the pump light, but the divergence angle of the mid-infrared laser is larger due to the thermal lens effect, the emitted light beams are separated by the ROE and then collimated by a shaping lens (namely, a third shaping lens 6 in the text), and the collimated light beams are 2mm in diameter and are emitted in parallel. At the last output end of the device, a window mirror with calcium fluoride is isolated from the external environment, so that the pollution of dust and water vapor is avoided.

The embodiments provided in the present application are only a few examples of the general concept of the present application, and do not limit the scope of the present application. Any other embodiments extended according to the scheme of the present application without inventive efforts will be within the scope of protection of the present application for a person skilled in the art.