CN113241575A

CN113241575A - Eye-safe laser structure

Info

Publication number: CN113241575A
Application number: CN202110174728.6A
Authority: CN
Inventors: 赵辉
Original assignee: Suzhou Tongren Laser Technology Co ltd
Current assignee: Suzhou Tongren Laser Technology Co ltd
Priority date: 2021-02-07
Filing date: 2021-02-07
Publication date: 2021-08-10

Abstract

The invention provides a human eye safety laser structure which can output laser with a human eye safety waveband, ensure the quality of a light beam and solve the problems of low output energy, easy damage of a laser crystal and the like of the existing laser; the erbium-doped fiber laser comprises a light source, erbium glass, a first reflector and a second reflector, wherein the first reflector and the second reflector are arranged at the light emitting end of the erbium glass, the light source is a pumping light source, pumping light emitted by the light source enters the erbium glass, the included angle between the normal line of the first reflector and the normal line of the light emitting surface of the erbium glass is a Brewster angle, and the resonant cavity formed by the first reflector, the second reflector and the erbium glass is V-shaped, so that the pumping light is in the resonant cavity and the gain is larger than the loss.

Description

Eye-safe laser structure

Technical Field

The invention relates to the technical field of laser equipment, in particular to a human eye safety laser structure.

Background

The laser technology is widely applied to the application fields of distance measurement, radar, remote sensing, medical treatment and the like, the wavelengths used by the laser in the distance measurement are 1.06 mu m, 1.5 mu m, 10.6 mu m and the like, but the 1.06 mu m and 10.6 mu m wavelengths allow the exposure of human eyes to be smaller, so that the laser easily causes great damage to the most sensitive human eyes in the moment, and particularly easily brings the risk of blindness to human personnel in battlefields and training; in addition, the existing laser technology is generally a linear cavity technology, but the main problem of the technology is that in order to reduce the influence of thermal effect on the output laser, the length of the resonant cavity is as small as possible, thus affecting the quality of the beam; meanwhile, the problems of low laser output energy, easy damage of laser crystals and the like exist, so that the research on the human eye safe waveband laser becomes very significant.

Disclosure of Invention

Aiming at the problems, the invention provides a human eye safety laser structure which can not only output laser with a safety waveband for human eyes, but also ensure the quality of light beams, and simultaneously solve the problems of low output energy, easy damage of laser crystals and the like of the existing laser.

The technical scheme is as follows: an eye-safe laser structure comprising a light source, characterized in that: the erbium-doped fiber laser comprises erbium glass, a first reflector and a second reflector, wherein the first reflector and the second reflector are arranged at the light emitting end of the erbium glass, the light source is a pumping light source, pumping light emitted by the light source enters the erbium glass, included angles between the normal lines of the first reflector and the second reflector and the normal line of the light emitting surface of the erbium glass are Brewster angles, and a resonant cavity formed by the first reflector, the second reflector and the erbium glass is V-shaped, so that the pumping light is in the resonant cavity and the gain is larger than the loss.

Further, the erbium glass has a refractive index of 1.531 at a wavelength of 1.54 um; the Brewster angle is 56.8 degrees;

further, the reflection angle of light entering into the erbium glass is larger than the critical angle, and the reflection angle is 33.1 °;

further, the laser device also comprises a Q-switched crystal which is arranged in the direction of an output light beam between the first reflecting mirror and the erbium glass;

furthermore, the Q-switched crystal adopts an active Q-switched crystal or a passive Q-switched crystal; the width-thickness ratio of the erbium glass is more than 2;

further, the wavelength of the pump light emitted by the light source is 940nm or 980 nm; the light source is emitted by a laser diode or a fiber laser;

furthermore, the first reflecting mirror and the second reflecting mirror both adopt plane reflecting mirrors or spherical reflecting mirrors; the mirror surfaces of the first reflector and the second reflector are plated with 940nm or 980nm full-reflection films and 1535nm high-reflection films;

the erbium-doped fiber laser further comprises a coupling lens with positive optical power, the light source is arranged on the side of the erbium glass, and the coupling lens is arranged between the light source and the erbium glass, so that pump light emitted by the light source enters the erbium glass from the side of the erbium glass after passing through the coupling lens;

further, the side face of the erbium glass adjacent to the coupling lens is plated with a 940nm or 980nm high-transmittance film and a 1535nm high-reflectance film;

further, the light source is arranged at one side end of the erbium glass, and the pump light emitted by the light source enters the erbium glass from the end face of the erbium glass.

The invention has the advantages that because the included angles between the normal lines of the first reflector and the second reflector and the normal line of the light-emitting surface of the erbium glass are Brewster angles, laser can be transmitted in the erbium glass through zigzag light paths, at the moment, different parts of light beams experience each region of temperature distribution in the same way in the thickness direction of the erbium glass, so the heat effect caused in the thickness direction is eliminated, the quality of the generated light beams is close to that of a TEM00 film, and meanwhile, the temperature adaptability is stronger; and the resonant cavity formed by the first reflector, the second reflector and the erbium glass is V-shaped, so that the miniaturization of the laser can be kept while the cavity length is increased, and the divergence angle of the light beam can be compressed when the cavity length is increased, so that the laser with a safe waveband for human eyes can be output, the quality of the light beam can be ensured, the problems that the existing laser is low in output energy, the laser crystal is easy to damage and the like are solved, and the laser has better economic use value.

Drawings

FIG. 1 is a schematic structural diagram of a first embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a second embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly or indirectly secured to the other element. When an element is referred to as being "connected to" another element, it can be directly or indirectly connected to the other element. The terms "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positions based on the orientations or positions shown in the drawings, and are for convenience of description only and not to be construed as limiting the technical solution. The terms "first", "second" and "first" are used merely for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "plurality" is two or more unless specifically limited otherwise.

In order to explain the technical solution of the present invention, the following detailed description is made with reference to the specific drawings and examples.

Example one

As shown in FIG. 1, the laser structure for human eye safety of the present invention comprises a light source, an erbium glass 5, and a first reflector 6 and a second reflector 7 disposed at the light-emitting end of the erbium glass 5, the erbium-doped fiber laser also comprises a coupling lens with positive focal power, the coupling lens can focus pump light at the middle position of erbium glass 5, the number of the coupling lens is two, the coupling lens is divided into a first coupling lens 3 and a second coupling lens 4, the light source is a pump light source, the number of the light source is two, the coupling lens is divided into a first light source 1 and a second light source 2, the light source is arranged at the side part of the erbium glass 5, the coupling lens is arranged between the light source and the erbium glass 5, so that the pump light emitted by the light source enters the erbium glass 5 from the side of the erbium glass 5 after passing through the coupling lens, namely, the first coupling lens 3 is arranged between the first light source 1 and the erbium glass 5, and the second coupling lens 4 is arranged between the second light source 2 and the erbium glass 5; the light source sends out pump light and gets into erbium glass 5, and the contained angle between the normal of first speculum 6, second speculum 7 and the normal of erbium glass 5 plain noodles is brewster angle 9, and the resonant cavity that first speculum 6, second speculum 7 and erbium glass 5 three formed is the V type, and makes pump light satisfy gain in the resonant cavity and be greater than the loss.

The refractive index of the erbium glass 5 at the wavelength of 1.54um is 1.531; brewster angle 9 is 56.8 °;

the reflection angle 10 and the reflection angle 11 of the light entering the erbium glass 5 are both larger than the critical angle, and the reflection angle 10 and the reflection angle 11 are both 33.1 °.

The laser device also comprises a Q-switched crystal 8, wherein the Q-switched crystal 8 is arranged in the direction of an output light beam between the first reflector 6 and the erbium glass 5; the generated laser is pulse laser by adding the Q-switched crystal 8; the Q-switched crystal 8 adopts an active Q-switched crystal 8 or a passive Q-switched crystal 8.

The width to thickness ratio of the erbium glass 5 is greater than 2, the preferred size of the erbium glass 5 is 2mm by 1mm by 8 mm.

The wavelength of pump light emitted by the light source is 940nm or 980 nm; the light source is emitted by a laser diode or a fiber laser.

The first reflector 6 and the second reflector 7 both adopt plane reflectors or spherical reflectors; the mirror surfaces of the first reflecting mirror 6 and the second reflecting mirror 7 are plated with 940nm or 980nm total reflection films and 1535nm high reflection films.

The side face of the erbium glass 5 adjacent to the coupling lens is plated with a 940nm or 980nm high-transmittance film and a 1535nm part high-reflection film so as to output laser.

Erbium glass 5 can be conductively heat-dissipated by bonding to copper or copper base with gallium adhesive or indium foil.

In the first embodiment, the pump light enters the erbium glass 5 from the side through the coupling lens, the erbium glass 5 undergoes energy level transition, and in an optical resonant cavity formed by the first reflector 6, the second reflector 7 and the erbium glass 5, when the gain is greater than the loss, laser light can be generated.

Preferably, the coupling lens is a cylindrical lens, and the cylindrical lens is preferably made of quartz glass.

The distance L1 between the light emitting surface of the pump light source and the coupling lens and the distance L2 between the coupling lens and the center of the erbium glass 5 are recorded, after the pump light source passes through the coupling lens, light spots are focused at the center of the erbium glass, and the numerical value of L1 and the radius of the coupling lens are reasonably designed according to the size and the divergence angle of the light emitting surface, so that the light spots at the center of the erbium glass are as small as possible, and light beams are coupled in as much as possible.

Example two

As shown in fig. 2, a second embodiment of the present invention is different from the first embodiment in that it is an end-pumping type, that is, a light source and a coupling lens are disposed at one end of an erbium glass 5, and pump light emitted from the light source enters the erbium glass 5 from the end face of the erbium glass 5 after passing through the coupling lens; in fig. 2, two right rectangular bars are a light source and a coupling lens from right to left; preferably, the coupling lens is a cylindrical lens, and the cylindrical lens is preferably made of quartz glass.

The second embodiment only illustrates the difference from the first embodiment, and the rest of the elements are arranged in the same way as the first embodiment.

In summary, compared with the prior art, because the included angles between the normals of the first reflector 6 and the second reflector 7 and the normal of the light-emitting surface of the erbium glass 5 are all the brewster angle 9, the laser can be transmitted in the erbium glass 5 through the zigzag optical path, at the moment, different parts of the light beam experience each region of the temperature distribution in the same way in the thickness direction, so that the heat effect caused in the thickness direction is eliminated, the light beam quality of the laser is close to that of a TEM00 film, and meanwhile, the temperature adaptability is stronger;

the resonant cavity structure is V-shaped, the miniaturization of the laser can be kept while the cavity length is increased, and the divergence angle of the light beam can be compressed when the cavity length is increased; in the prior art, in order to compress the beam divergence angle, the cavity length needs to be increased, however, the increase of the cavity length causes the thermal effect of the erbium glass 5 to be more obvious, and the laser output quality is seriously influenced; compared with the prior art, the invention adopts a side pumping mode, greatly enhances the output power of the laser through a V-shaped cavity structure, can reach about 50mJ, and compresses the divergence angle of the laser.

The laser output of the invention can be set as double output or single output according to the situation, and only by changing the reflectivity of the reflector, thereby bringing the beneficial effect that in the heterodyne measurement optical system, one path of light can be set as local oscillator light and the other path as signal light without adopting a light beam splitter.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. An eye-safe laser structure comprising a light source, characterized in that: the erbium-doped fiber laser comprises erbium glass, a first reflector and a second reflector, wherein the first reflector and the second reflector are arranged at the light emitting end of the erbium glass, the light source is a pumping light source, pumping light emitted by the light source enters the erbium glass, included angles between the normal lines of the first reflector and the second reflector and the normal line of the light emitting surface of the erbium glass are Brewster angles, and a resonant cavity formed by the first reflector, the second reflector and the erbium glass is V-shaped, so that the pumping light is in the resonant cavity and the gain is larger than the loss.

2. An eye-safe laser structure as claimed in claim 1, wherein: the refractive index of the erbium glass at the wavelength of 1.54um is 1.531; the brewster angle is 56.8 °.

3. An eye-safe laser structure as claimed in claim 2, characterized in that: the reflection angle of light entering the erbium glass is larger than the critical angle, and the reflection angle is 33.1 °.

4. An eye-safe laser structure as claimed in claim 1, wherein: the erbium-doped fiber laser further comprises a Q-switched crystal, wherein the Q-switched crystal is arranged in the direction of an output light beam between the first reflecting mirror and the erbium glass.

5. An eye-safe laser structure as claimed in claim 4, characterized in that: the Q-switched crystal adopts an active Q-switched crystal or a passive Q-switched crystal; the width-thickness ratio of the erbium glass is more than 2.

6. An eye-safe laser structure as claimed in claim 1, wherein: the wavelength of the pump light emitted by the light source is 940nm or 980 nm; the light source is emitted by a laser diode or a fiber laser.

7. An eye-safe laser structure as claimed in claim 1, wherein: the first reflector and the second reflector both adopt plane reflectors or spherical reflectors; the first reflector and the second reflector are both plated with 940nm or 980nm total reflection films and 1535nm high reflection films.

8. An eye-safe laser structure as claimed in any one of claims 1 to 7, wherein: the erbium-doped fiber laser further comprises a coupling lens with positive optical power, the light source is arranged on the side of the erbium glass, and the coupling lens is arranged between the light source and the erbium glass, so that pump light emitted by the light source enters the erbium glass from the side surface of the erbium glass after passing through the coupling lens.

9. An eye-safe laser structure as claimed in claim 8, wherein: the side face of the erbium glass adjacent to the coupling lens is plated with a 940nm or 980nm high-transmittance film and a 1535nm high-reflectance film.

10. An eye-safe laser structure as claimed in any one of claims 1 to 7, wherein: the light source is arranged at one side end of the erbium glass, and pump light emitted by the light source enters the erbium glass from the end face of the erbium glass.