CN106549294A - The hysteroscope of solid state laser and the resonator and solid state laser using which - Google Patents

Abstract

A cavity mirror of a solid-state laser and a resonant cavity and a solid-state laser using the same. The cavity mirror includes a rear cavity mirror and an output mirror, which are respectively located on the left and right sides of the solid-state laser resonator, and the rear cavity mirror and the output mirror face the inside of the resonator The center of the surface is coated with a high reflection film and a partial reflection film respectively, and the diameters of the high reflection film and the partial reflection film are 1 to 3mm. In the present invention, the diameter of the high reflection film and the partial reflection film is 1.2 to 2 times the diameter of the light spot on the cavity mirror when the solid laser is output at the highest power. Therefore the loss of the highest power of the laser by the solid-state laser of the present invention is extremely small; when the laser output is in the middle power section, since the spot diameter on the inner side of the cavity mirror is greater than the coating diameter, the multi-order transverse mode with a spot diameter greater than the coating diameter will be limited from vibrating , the spot size on the cavity mirror is limited to the diameter of the coating, and the reduction of the number of high-order modes will make the beam divergence angle smaller, thereby improving the beam quality in the middle power range.

Description

Cavity mirror of solid-state laser and resonant cavity and solid-state laser using it

technical field

The invention belongs to the field of laser technology, and more specifically relates to a cavity mirror of a solid laser, a resonant cavity and a solid laser using the same.

Background technique

It is extremely difficult for solid-state lasers using rod-shaped crystals as laser working materials to obtain high-power laser output through small-diameter fibers. The reason is that under high pump power, the central region of the crystal rod will form a very high temperature due to the superposition of pump light, while the surface of the crystal rod is used as a heat dissipation surface and its temperature is relatively low, so the radial direction of the crystal rod has extremely high temperature. The temperature gradient will form a very strong refractive index gradient inside the crystal, resulting in a severe thermal lens effect. At this time, the crystal rod is equivalent to a lens whose diopter becomes larger as the pump power increases. In the high-power laser resonator, a flat resonator with a symmetrical structure is mainly used. The output power has a maximum value as the thermal lens increases continuously. After that, when the focal length of the thermal lens is less than a quarter of the optical length of the resonator, the resonator Entering the unstable region leads to a sharp drop in output power, and the beam quality of the laser shows a trend of first getting worse and then getting better with the increase of the thermal lens of the crystal rod. The beam quality is excellent at the rated power of the laser and the beam quality worst quality. When the laser is coupled with the fiber, the fiber is usually selected according to the worst beam quality. Although the laser generally works near the rated power, the beam parameter product BPP value of the output light is much smaller than the BPP value of the energy-transmitting fiber. However, if the rated power If the optical fiber is selected for the beam quality at the center, the coupling loss in the middle power section is very large, and it is easy to burn the optical fiber. In order to be able to transmit energy using an optical fiber that matches the beam quality at the rated power on the premise of ensuring that the fiber is not burned, the coupling efficiency is high, and the output power is high, there is an urgent need for a method that can significantly improve the beam quality in the mid-power range. Thereby reducing the coupling loss.

Contents of the invention

Based on the above technical problems, the main purpose of the present invention is to provide a cavity mirror of a solid-state laser, a resonator and a solid-state laser using the same, to solve at least one of the above technical problems.

In order to achieve the above object, as an aspect of the present invention, the present invention proposes a cavity mirror of a solid-state laser, including a rear cavity mirror and an output mirror, which are respectively located on the left and right sides of the solid-state laser resonator, the rear cavity mirror and the output mirror The center of the surface facing the inner side of the resonant cavity is respectively coated with a high reflection film and a partial reflection film, and the diameters of the high reflection film and the partial reflection film are 1-3 mm.

Further, the diameter of the above-mentioned high reflection film and partial reflection film is 1.2 to 2 times of the spot diameter on the corresponding cavity mirror when the solid-state laser outputs the highest power.

Further, the reflectivity of the above-mentioned high reflective film is greater than 99%.

Further, the reflectance R of the partial reflection film satisfies the condition of 20%≦R≦80%.

Further, the surface of the output mirror facing the outside of the resonant cavity is coated with an anti-reflection film, and the reflectivity of the anti-reflection film is less than 1%.

Further, the above-mentioned rear cavity mirror and output mirror have a diameter of 10-25 mm and a thickness of 3-6 mm.

In order to achieve the above object, the present invention also proposes a resonant cavity of a solid-state laser, including the above-mentioned cavity mirror of the solid-state laser.

Further, the resonant cavity of the above-mentioned solid-state laser also includes an all-solid-state laser head or a lamp-pumped solid-state laser head.

When in use, the center of the high-reflection film and the center of the partial reflection film are on the extension line of the central axis of the crystal rod in the all-solid-state laser head or the lamp-pumped solid-state laser head.

In order to achieve the above object, the present invention also proposes a solid-state laser, including the resonant cavity of the above-mentioned solid-state laser.

The cavity mirror of the solid-state laser proposed by the present invention and the resonant cavity and the solid-state laser applying it have the following beneficial effects:

1. The cavity mirror of the solid-state laser proposed by the present invention, its rear cavity mirror is coated with a high-reflection film, and the output mirror is coated with a partially reflective film. The coating diameter is determined according to the spot diameter on the cavity mirror when the laser is in the highest output state, and its size 1.2 to 2 times the spot diameter. Therefore, the loss of the highest power of the laser is extremely small. When the laser output is in the middle power range, since the diameter of the spot on the inner surface of the cavity mirror is larger than the diameter of the coating, the multi-order transverse mode that limits the diameter of the spot to be larger than the diameter of the coating will start to oscillate, and the size of the spot on the cavity mirror will be limited to the diameter of the coating. At the same time The reduction in the number of high-order modes will make the beam divergence angle smaller, thereby improving the beam quality in the mid-power range.

2. The solid-state laser proposed by the present invention improves the beam quality in the middle power section, so it is possible to select an optical fiber that matches the beam quality of the rated power, and it can maintain efficient coupling in the full power section, solving the problem of small core diameter The coupling efficiency of the optical fiber in the middle power section is low, which is a technical problem that is easy to damage the optical fiber.

Description of drawings

Fig. 1 is a structural schematic diagram of a cavity mirror of a solid-state laser proposed by an embodiment of the present invention;

Fig. 2 is an embodiment of the present invention for determining the coating diameter of the cavity mirror, and measuring the optical device diagram of the spot size on the cavity mirror;

Fig. 3 is a schematic diagram of fiber coupling of a solid-state laser proposed by an embodiment of the present invention;

FIG. 4 is a comparison diagram of the coupling efficiency of the solid-state laser proposed by an embodiment of the present invention with and without the solid-state laser cavity mirror in FIG. 1 .

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The invention discloses a cavity mirror of a solid-state laser, which comprises a rear cavity mirror and an output mirror, which are respectively located on the left and right sides of the resonant cavity of the solid-state laser. The rear cavity mirror and the output mirror are respectively coated with High reflection film and partial reflection film, the diameter of high reflection film and partial reflection film is 1-3mm.

Preferably, the diameter of the above-mentioned high-reflection film and partial reflection film is 1.2 to 2 times the diameter of the spot on the corresponding cavity mirror at the highest power output of the solid-state laser. Preferably, the diameter of the high-reflection film and partial reflection mirror is the highest power output of the solid-state laser. 1.5 times the spot diameter on the rear cavity mirror. Therefore, the loss of the rated power of the laser is extremely small; when the output of the laser is in the middle power range, since the diameter of the spot on the inner surface of the cavity mirror is larger than the diameter of the coating, the vibration of the multi-order transverse mode with a diameter of the spot larger than the diameter of the coating will be limited, and the cavity mirror will The spot size is limited to the diameter of the coating, and the reduction in the number of high-order modes will make the beam divergence angle smaller, thereby improving the beam quality in the mid-power range.

The reflectivity of the above-mentioned high-reflection film is greater than 99%, and the reflectivity R of the above-mentioned partial reflection film satisfies the condition of 20%≤R≤80%; preferably, for continuous laser output, the reflectivity of the partial reflection film is 70%, and for pulsed laser Output, the reflectivity of the partially reflective film is 20%. The surface of the output mirror facing the outside of the resonant cavity is coated with an anti-reflection film, and the reflectivity of the anti-reflection film is less than 1%. Preferably, the diameter of the anti-reflection film is not smaller than the diameter of the partial reflection film.

Preferably, the above-mentioned rear cavity mirror and output mirror have a diameter of 10-25 mm and a thickness of 3-6 mm.

Preferably, the rear cavity mirror and the output mirror are mechanically polished frosted surfaces before coating, rough surfaces marked by carbon dioxide lasers, or uncoated substrate surfaces.

Based on the above-mentioned cavity mirror of the solid-state laser, the present invention discloses a resonant cavity of the solid-state laser, including the above-mentioned cavity mirror of the solid-state laser.

The resonant cavity of the above-mentioned solid-state laser also includes a laser head, and the laser head is preferably an all-solid-state laser head or a lamp-pumped solid-state laser head.

When in use, the center of the high reflection film of the rear cavity mirror and the center of the partial reflection film of the output mirror are on the extension line of the central axis of the crystal rod in the laser head.

Based on the above-mentioned cavity mirror of the solid-state laser, the present invention also proposes a solid-state laser, including the above-mentioned cavity of the solid-state laser.

The solid-state laser can select the fiber that matches the beam quality of the rated power for fiber coupling, so as to maintain high-efficiency coupling in the full power range, and solve the problem of low coupling efficiency of the small-core fiber in the middle power range and easy damage to the fiber. technical challenge.

The cavity mirror of the solid-state laser proposed by the present invention, the resonant cavity and the solid-state laser to which it is applied are described in detail below through specific embodiments.

Example 1

As shown in Figure 1, this embodiment proposes a cavity mirror for a solid-state laser, including a rear cavity mirror 11 and an output mirror 12, and the surfaces of the rear cavity mirror 11 and the output mirror 12 facing the inner side of the resonator are respectively coated with a high reflection film. And the partial reflection film, the diameter of the high reflection film and the partial reflection film is 1.5 times of the spot diameter on the rear cavity mirror when the solid-state laser has the highest power output.

The reflectivity of the high-reflection film of the rear cavity mirror 11 to the 1064nm laser power is 99.5%, and its surface facing the outside of the resonator is not coated; the reflectivity of the partial reflection film of the output mirror 12 is 70% to the 1064nm laser power, and it faces the resonator The entire surface outside the cavity is coated with an anti-reflection film, and the reflectivity of the anti-reflection film to 1064nm laser power is 0.5%. The uncoated part of the rear cavity mirror 11 and the output mirror 12 is the surface of the lens base. The diameter of the rear cavity mirror and the output mirror is 20mm, and the thickness is 4mm.

Wherein the size of the solid-state laser spot size adopts the optical device measurement as shown in Figure 2, and this device is with common rear cavity mirror 13 (on the surface facing the laser head, the reflectivity R of 1064nm laser is plated on the high-reflection film of > 99.5%) , common output mirror 14 (on the surface facing the laser head, the high-reflection coating to the 1064nm laser reflectivity R=70% is plated, and the anti-reflection film to the 1064nm laser reflectivity R＜0.5% is plated on the surface facing away from the laser head) Together with the 1.2kW all-solid-state laser head 15, it forms a flat and symmetrical resonant cavity, and the physical cavity length of the resonant cavity is 600mm. The maximum power output by the resonator is emitted to the light absorber 17 through the 45° reflector 16, and the diameter of the laser spot on the output mirror 14 is measured by the CCD 19 with the imaging device 18, and the diameter of the spot is 1.6 mm.

Then the diameter of the partial reflection film coated on the surface of the output mirror 12 facing the inner side of the resonant cavity is 1.6×1.5=2.4mm. Because it is a symmetrical cavity, the diameter of the high reflection film plated on the surface center of the rear cavity mirror 11 towards the inner side of the cavity is also 2.4mm.

Using the cavity mirror of the above-mentioned solid laser, this embodiment also proposes a resonant cavity of the solid laser, the laser head of the resonant cavity adopts an all-solid-state laser head, and the center of the high reflection film of the rear cavity mirror 11, and the part of the reflective film of the output mirror 12 The center is on the extension line of the central axis of the crystal rod in the laser head.

Example 2

Based on the resonant cavity of the solid-state laser in Embodiment 1, this embodiment proposes a solid-state laser, using the optical device shown in Figure 2, wherein the ordinary rear cavity mirror 13 is replaced by the rear cavity mirror 11 in Embodiment 1, and the The common output mirror 14 is replaced by the output mirror 12 in Embodiment 1, and the corresponding optical element for measuring the light spot in FIG. 2 is removed.

As shown in Figure 3, it is an example diagram of the application of the solid-state laser proposed in this embodiment. A collimation and focusing system 20 is added to the solid-state laser. The device can be used in the laser welding process of metal parts such as kitchen hardware production and automobile body-in-white welding.

In order to illustrate the advantages of the solid-state laser proposed in this embodiment compared with the existing solid-state laser, the coupling efficiency of the optical device in Fig. 3 is measured as a function of the output power; and the rear cavity mirror 11 and the output mirror 12 in Fig. Cavity mirror 13 and ordinary output mirror 14, measure the coupling efficiency of the optical device in Fig. 3 with the change of output power when using common back cavity mirror 13 and common output mirror 14, and the coupling efficiency under two kinds of situations changes with output power By comparison, the comparison diagram shown in Figure 4 is obtained. As can be seen from Figure 4, the common rear cavity mirror 13 and the common output mirror 14 are replaced by the rear cavity mirror 11 and the output mirror adopted by the solid-state laser proposed in this embodiment 12. When the coupling efficiency is greatly improved, the beam quality of the solid-state laser proposed in this embodiment is significantly improved, and at the same time, a higher output power can be guaranteed.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (9)

1. A cavity mirror of a solid-state laser, comprising a rear cavity mirror and an output mirror, which are respectively located on the left and right sides of the solid-state laser resonator, characterized in that: the rear cavity mirror and the output mirror are towards the inside of the resonator The center of the surface is coated with a high reflection film and a partial reflection film respectively, and the diameters of the high reflection film and the partial reflection film are 1-3mm. 2 . The cavity mirror of a solid-state laser according to claim 1 , wherein the diameters of the high-reflection film and the partially-reflection film are 1.2 to 2 times the spot diameter on the cavity mirror at the highest power output of the solid-state laser. 3. The cavity mirror of a solid-state laser as claimed in claim 1, wherein the reflectivity of the high reflective film is greater than 99%. 4. The cavity mirror of a solid-state laser according to claim 1, wherein the reflectance R of the partially reflecting film satisfies the condition of 20%≤R≤80%. 5 . The cavity mirror of a solid-state laser according to claim 1 , wherein the surface of the output mirror facing the outside of the resonator is coated with an anti-reflection coating, and the reflectivity of the anti-reflection coating is less than 1%. 6. The cavity mirror of a solid-state laser according to claim 1, wherein the rear cavity mirror and the output mirror have a diameter of 10-25mm and a thickness of 3-6mm. 7. A resonant cavity of a solid-state laser, characterized by comprising the cavity mirror of a solid-state laser according to any one of claims 1-6. 8. The resonant cavity of the solid-state laser according to claim 7, wherein the resonant cavity of the solid-state laser further comprises an all-solid-state laser head or a lamp-pumped solid-state laser head. 9. A solid-state laser, characterized by comprising the resonant cavity of the solid-state laser as claimed in claim 8.