KR20120122605A - Small size high power solid-state laser generator that have high quality beam that use laser diode - Google Patents

Abstract

PURPOSE: A micro type solid-state laser generator for generating a high quality beam using a laser diode is provided to effectively remove heat from the laser diode using a laser diode cooling pin with high efficiency. CONSTITUTION: A laser diode(4) excites a laser gain medium(8). An appropriately sized entrance port(3) passes through beams which comes out of the laser diode. A reflector(9) reflects laser diode beams having an oscillation line width less than 1 mm. Both end blocks(2) fix the reflector. A laser diode cooling module(6) cools the laser diode having the oscillation line width less than 1 mm. A groove is carved on the surface of a laser gain medium. A host medium(10) does not include the gain medium in both sides. A laser gain medium supporter(1) directly fixes the laser gain medium.

Description

Small size high power solid-state laser generator that have high quality beam that use laser diode}

  The present invention relates to a laser diode excited solid state laser generator. Solid lasers that pump the laser diode to excite the active material contained in the laser crystal include Nd: YAG, Nd: YVO4, Nd: GdVO4, Nd: YLF, and Er: YAG.

  The solid state laser has a lamp pumping method and a laser diode pumping method according to the efficient aspect in which the active material contained in the laser crystal is excited, and there are pulse oscillation type and continuous oscillation type. In the case of the continuous oscillation type, the ramping is replaced by the laser diode method. In the case of the pulse oscillation type, the lamp pumping method enables the pumping of relatively high optical density, while the laser diode method has only the peak output of about twice the continuous oscillation output value. Since the pump can not be pumped, the oscillation of the pulse type laser of about microseconds or milliseconds (msec) has not replaced the lamp method.

  The present invention relates to a laser diode excited solid state laser generator. Solid lasers that pump the laser diode to excite the active material contained in the laser crystal include Nd: YAG, Nd: YVO4, Nd: GdVO4, Nd: YLF, and Er: YAG. The excitation method using a lamp has an energy conversion efficiency of about 2.5% and the excitation method using a laser diode having an oscillation line width of about 3nm is about 30%.

  The solid state laser has a lamp pumping method and a laser diode pumping method according to the efficient aspect in which the active material contained in the laser crystal is excited, and there are pulse oscillation type and continuous oscillation type. In the case of the continuous oscillation type, the ramping is replaced by the laser diode method. In the case of the pulse oscillation type, the lamp pumping method enables the pumping of relatively high optical density, while the laser diode method has only the peak output of about twice the continuous oscillation output value. Since the pumping is not possible, the pulse type laser oscillation of about microseconds or milliseconds (msec) does not replace the lamp method.

   The shape of the gain medium has a circular rod shape and a plate shape. In the case of the circular rod shape, a groove is formed on the surface of the gain medium to increase the contact area with the cooling water, thereby reducing the thermal lens effect, and the crystal having difficulty in contact with the cooling water for support. Both ends are bonded with a crystal that does not contain an active material to improve beam quality and conversion efficiency (patented by China DJ-laser).

As a method of focusing the laser diode light on the gain medium, the laser diode light is focused on the optical fiber and the transmitted beam is transmitted to the gain medium (US Patent 5,548,608). (D. Golla et al. 62-W CW TEM00 Nd: YAG laser side-pumped by fiber coupled diode laser, Opt. Lett., Vol. 21, 210 (1996)), and The method of reaching the vicinity of the gain medium through the waveguide path in which the laser diode light is formed directly on the reflector, except the thin entrance part through which the laser diode light must pass outside the cylindrical glass tube through which the coolant flows for cooling the gain medium, i.e., the reflection The part that needs to be applied is total reflection silver coating, which directly transmits the laser diode light directly to the laser gain medium (Louis Cabaret et al., Rod la). ser with optical pumping from a source having a narrow emitting area, US Patent, 5,033,058), and the method according to the inventor's prior art (Patent, 10-0348998, 0519226).

  The present invention utilizes the characteristics of a laser diode to excite a solid gain medium using a laser diode to generate a laser by high efficiency excitation.

 For this purpose, a reflector was used to enable uniform pumping of the laser gain medium by using the prior art of the inventor (0519226). The laser diode was brought close to the entrance port with the antireflective coating of the reflector so that light was absorbed directly through the entrance hole and absorbed by the gain medium. The pumping wavelength was selected in consideration of the concentration and light absorption of neodymium (Nd). By optimizing the direct and indirect absorption of the pumped light in the gain medium by controlling the distance between the crystal and the laser diode, the gain medium.

However, the oscillation line width of the pumping laser diode of the present inventors prior art (0519226) is wider to 3 nm, so that the conversion efficiency is lowered, and the thermal lens effect is increased and birefringence is high, which hinders beam quality. In addition, in order to maintain a stable center wavelength at high power due to the movement of the center wavelength according to the temperature of the laser diode, a cooling module having a special cooling fin and a high temperature controlled large capacity cooler are required. In addition, the thermal lens effect at both ends of the gain medium, that is, the part which is not in contact with the cooling water, changes depending on the external humidity and temperature, thus acting as an instability factor of the laser output. The higher the output, the lower the concentration of the gain medium, which has its limitations. For Nd: YAG, 0.6W% is the limit.

The oscillation line width of the pumping laser diode according to the prior art (0519226) of the present inventors is widened to 3 nm to reduce the conversion efficiency, as well as to increase the thermal lens effect and increase the birefringence to solve the problem of impairing the beam quality. In addition, in order to maintain a stable center wavelength at high power due to the movement of the center wavelength according to the temperature of the laser diode, a cooling module having a special cooling fin and a high temperature controlled large capacity cooler are required. In addition, the thermal lens effect at both ends of the gain medium, that is, the part which is not in contact with the cooling water, changes depending on the external humidity and temperature, thus acting as an instability factor of the laser output. The higher the output, the lower the concentration of the gain medium, which has its limitations. For Nd: YAG, 0.6W% is the limit.

As described above, the present invention can achieve a simple laser beam transmission without using an optical system and uniform laser gain medium excitation by using a method of exciting a laser diode in the reflector through a laser diode through an inlet. In addition, by effectively removing the heat of the laser diode using a high-efficiency laser diode cooling fins, a high-efficiency high-performance laser generator capable of generating a laser stably for a long time despite the change in the coolant temperature is possible.

Overall scale structure diagram of laser generator

According to the present invention, several laser diodes 4 having a long straight shape are arranged on the concentric circumference of the laser gain medium 8 in the longitudinal direction of the medium to excite the laser gain medium 8 from the side to oscillate the laser. The device is described.

   The laser diode 4 has a narrow and long linear light emitting surface and has a characteristic of spreading with a very large divergence angle of about 40 ° in the short axis direction and about 10 ° in the major axis direction. The present invention efficiently transmits the laser beam having such a large divergence angle to the laser gain medium 8 having a cylindrical structure in the reflector 9 to uniformly excite the laser gain medium 8 to achieve high efficiency. A spatially uniform laser beam distribution is obtained. And using the cooling fins to prevent the damage caused by the fluctuation caused by the temperature change of the laser diode (4) and excessive temperature rise of each part.

The laser diode is therefore attached to the chiller module 6 which is cooled with water. In the cooling device module 6, cooling fins having various shapes of cross sections are extended in the longitudinal direction in which the cooling water flows, thereby effectively transferring heat generated from the laser diode 4 to the cooling water. The material for the cooling fins is made of oxygen-free copper, which has good thermal conductivity, and the surface has an anti-corrosion coating. The laser diode beam is absorbed into the laser gain medium 8 through the entrance port 3, the coolant pipe 12, and the coolant 7. The shape of the entrance hole 3 is a long rectangle similar to the output surface of the laser diode, and the width and length of the entrance hole 3 are the minimum dimensions that do not interfere with the progress of the laser diode light in consideration of the beam spread of the laser diode. Lengthen. When the width dimension of the entrance hole 3 is too large, the reflecting area is reduced to reduce the efficiency, so that the distance between the entrance hole 3 and the laser diode emitting surface is appropriately taken into consideration. The beam that has not been absorbed by the laser gain medium 8 and has passed through or passed through the laser gain medium 8 is scattered in the plane of the reflector 9. The scattered laser beam is again absorbed in the laser gain medium 8 or reflected once again in another diffuse reflection plane and then in the laser gain medium 8. An integrated variable reflector is used for reflection.

The internal structure of the reflector 9 device is of cylindrical symmetry. The laser medium is located at the center of the structure inside the reflector 9 and absorbed directly. The laser diode 4 and the beam reflected from the diffuse reflection surface are absorbed symmetrically. In addition, the ratio of directly absorbed beams and non-reflected beams is adequate so that uniform excitation occurs over the front face of the laser gain medium 8. Uniform excitation distribution is necessary to minimize the thermal lens effect and the birefringence effect due to heat.

In the present invention, the use of the reflector 9 is an important process for inducing an excited state with a uniform distribution. In the diffuse reflection process, the laser diode beam loses its initial direction and is directed in an arbitrary direction. In the direct absorption process, since the beam is absorbed by a beam having a predetermined direction, it is not evenly absorbed over the front end surface of the laser gain medium 8. Therefore, the distribution of the absorbed beam is in a state where the gain medium toward the excitation direction is further excited to directly reflect the effect of the distribution of the excitation laser diode beam. If the cooling modules having several laser diodes attached in a line in the longitudinal direction of the gain medium are divided at regular angles on the circumference of the gain medium and increased in various directions, the excitation uniformity by direct absorption increases with an increase in the excitation direction.

  Depending on the diameter of the laser medium and the concentration of the active substance, the diameter of the internal reflecting surface of the reflector 9 is slightly different. Therefore, it has been proved that high efficiency is possible even with a simple structure as in the present invention. In addition, even if the device was operated for several hundred hours or more, the oscillation of the output was very stable, within 2%.

There are additional devices and functions that achieve high efficiency in the present invention. Bonding to both sides of the crystal 10 without the laser gain medium reduces the thermal lens effect.

 One of the important devices that have obtained stable output is the structure that does not use sleeves at both ends of the block, which directly supports the laser gain medium (8) to prevent fine vibration of the laser gain medium (8) due to the coolant flow and thus oscillation of the laser beam. Minimization of path shaking. In the present invention, a block at both ends directly supports the laser gain medium 8, and has a very stable structure.

The blocks 2 at both ends also serve to distribute the cooling water at the same time. Since the coolant 7 flows along the laser gain medium support 1 in which the inlet is gradually narrowed, the coolant 7 flows to the surface of the laser gain medium 8 very quickly and causes an increase in pressure. It also creates turbulence on the surface of the laser gain medium 8 to induce effective cooling.

Cooling water can be introduced into one or both ends of the block 2 at both ends, so that the cooling water can be connected and flowed very easily.

The middle block mechanically and firmly supports both blocks and the laser diode cooling module, while simultaneously sealing them to protect the interior from external influences.

In addition, the blocks at both ends are invented so that the cooling water can flow simultaneously not only in the laser gain medium 8 but also in the laser diode cooling module 6. Cooling fins having various cross-sections were attached to the cooling module of the laser diode in parallel with the direction in which the cooling water flows. As a result, the flow of the cooling water is smoothed so that the cooling can be efficiently performed without any pressure drop. In this way it is possible to provide a very simple and simple cooling water connection passage to effectively cool the entire apparatus.

In addition, the blocks (2) at both ends are made of titanium, stainless steel, engineering plastics, acrylics, etc., which can minimize the contamination of optical elements. Was applied.

The base block 14 fixes the blocks 2 in parallel, and serves to change the direction of the inlet 11 and the outlet 16 of the coolant and the mechanical and electrical components for coupling with other devices. 13) is arranged, and a space is provided inside the base block to insert an electronic circuit to give usage records and self-management functions.

(1) supports (2) blocks on both ends (3) laser diode light entrance
(4) laser diodes (5) coolant flow tubes (6) laser diode cooling modules
(7) cooling water (8) crystals with gain medium (9) reflectors
(10) Crystals without gain medium (11) Coolant inlet and outlet
(12) Flow tube fixtures (13) Electric / electronic lines (14) Foundation blocks
(15) Protective case cover (16) Cooling water inlet and outlet

Claims (2)

In an apparatus for exciting a laser gain medium 8 using a laser diode 4 having an oscillation line width of 1 nm or less, a plurality of oscillation line widths positioned in the direction of the laser optical axis length on the same circumference as a light source for exciting the laser gain medium 8. A laser diode 4 of 1 nm or less, an entrance hole 3 of suitable size for passing a beam from the laser diode 4 of 1 nm or less in oscillation line, a laser diode 4 of 1 nm or less in oscillation line width, and A reflector 9 for reflecting a laser diode 4 beam having an oscillation line width emitted through the light incidence hole 3 of 1 nm or less,
Both ends of the block 2 for fixing the reflector 9, cooling fins having a cross section of various shapes for cooling the laser diode 4 having the oscillation line width of 1 nm or less, and a laser diode cooling module 6 forming a body ), And bonding the host medium 10 having the grooves engraved on the surface of the laser gain medium 8 and not including the gain medium on both sides thereof, and a laser gain medium support 1 for directly fixing the oscillation. A stainless steel that simultaneously supports and fixes the laser diode cooling module 6 and the cooling module and the protective cover 15 simultaneously allowing the cooling water for cooling the laser diode having a line width of 1 nm or less to flow in the direction of the laser gain medium and the cooling fins of various cross-sections. A laser die provided to cool the blocks 2 at both ends, the reflector 9, and the laser diode 4 having an oscillation line width of 1 nm or less in titanium. A laser diode having a plurality of oscillation line widths of 1 nm or less arranged in concentric circles is characterized by the structure in which the cooling module 6, the block 2 at both ends, the protective cover 15, and the base block 14 are integrally formed. Solid state laser generator using. The material of the cylindrical reflector 9 is a gold-coated material having a high reflectance, a silver-coated material, a spectralon, a ceramic material, as well as an integral variable reflector, and the base block 14 fixes both blocks 2 in parallel. In addition, a mechanical element and an electro-electric element 13 for arranging the direction of the inlet 11 and the outlet 16 of the coolant and coupling with other devices are arranged, and the electronic circuit is provided by providing a space inside the base block. Solid-state laser generator using a laser diode (4) having a plurality of oscillation line widths of 1 nm or less arranged on the concentric circumference to give a record of use, self-management function by inserting a.

Images