KR100396676B1 - Apparatus cooling laser solid - Google Patents

Abstract

The present invention relates to a Diode Pumped Solied State (DPSS) laser, and more particularly, to a solid state laser cooling apparatus for reducing the thermal lens effect.

Such a solid state laser cooling apparatus according to the present invention includes a reflector for changing an optical path of focused light, a laser medium for generating a resonant wavelength of the changed light, a cooling window for cooling the laser medium, and the laser medium and a cooling window. And an output coupler for forming a resonant structure with the laser medium.

Description

Apparatus cooling laser solid

The present invention relates to a Diode Pumped Solied State (DPSS) laser, and more particularly to a solid state laser cooling structure that reduces the thermal lens effect.

As is known, lasers combine the operation of optical and electronic devices with Light Amplification by Stimulated emission of Radiation (LASER).

With the development of the laser has been developed in various ways, such as industrial, medical, research. In particular, researches are now being made on the methods that can be applied to home display media, and DPSS (Diode Pumped Solid State) laser is most likely as a small size, high efficiency, and high power visible light laser for home use.

1 is a schematic diagram of a conventional DPSS laser configuration.

Referring to FIG. 1, a conventional DPSS laser includes a pumping laser diode 1, a focusing optical system 2, a first reflector 3, a laser medium 4, a second reflector 5, and a nonlinear material 6 ( Nonlinear Optical Material) and the output coupler (7).

The DPSS laser configured as described above focuses the light (eg, 808 nm) of the pumping laser diode 1 on the laser medium 4 with the focusing optical system 2, and emits light of infrared wavelength in the laser medium 4. (Eg, 1064 nm / 914 nm) is generated, and this light causes resonance by the output coupler 7.

The light having the resonant infrared wavelength passes through the nonlinear material and is converted (eg, 532 nm / 457 nm) to a wavelength of half (λ / 2) of the resonant wavelength by SHG (Second Harmonic Generation) action of the material.

2 is a view showing a change in refractive index of a material due to general heat.

Referring to FIG. 1, in the laser medium 4 and the nonlinear material 6, heat is generated by energy of pumping light or resonant light, which causes a change in refractive index of the material.

However, since the amount of energy varies between the center and the periphery of the material, a difference in refractive index between the center and the periphery occurs.

When the refractive index difference occurs in the optical material, the optical path is changed according to the degree to act as a lens, which is called a thermal lens effect.

3 is a view illustrating a lens effect due to general heat.

Referring to FIG. 3, when a is not pumped light, that is, when no thermal lens effect occurs, and b is incident to pumping light at the center, the optical path is changed to generate a lens effect. Shows that

The lower part of the figure shows a conjugated optical system which has the same effect as a phenomenon generated by heat.

In the case of the thermal lens effect, it is shown that the material in the form of a block acts as a convex lens or a concave lens depending on the material.

4 is a diagram illustrating a general stable resonance condition.

Referring to Figure 4, it shows a condition that the laser can be stably resonated,

G1 = 1-L / R1

If we set G2 = 1-L / R2,

Stable resonator conditions,

0 <G1 G2 <1

If the above resonator conditions are not satisfied, the laser cannot oscillate because resonance is not performed.

However, when the pumping light is focused at a high output in order to obtain a high output from the DPSS laser, the thermal lens effect is severely generated, and thus the laser resonance condition is broken, resulting in an unstable state as shown in FIG. 5.

6 is a view showing a solid state laser for reducing the conventional thermal lens effect.

Referring to FIG. 6, Melles Griot Patent USP5796766 is a method for reducing the thermal lens effect.

The cooling structure of the solid-state laser that reduces the thermal lens effect disperses the central heat in a short time by bonding optical materials (eg, sapphire / YAG) with excellent heat transfer rate to both sides of the laser medium causing the thermal lens effect. Alleviated the thermal lens effect.

Even when using a solid laser cooling structure that reduces the thermal lens effect, there is a disadvantage in that there is a limit in alleviating the thermal lens effect when the light conversion efficiency is low, such as the current blue laser oscillation.

Accordingly, it is an object of the present invention to provide a high power solid state laser cooling structure which reduces the thermal lens effect by achieving cooling of a material quickly in view of the problems of the prior art mentioned above.

1 is a schematic diagram of a conventional DPSS laser configuration

2 is a view showing a change in refractive index of a material due to general heat

3 is a view showing a lens effect due to general heat

4 is a diagram showing a general stable resonance condition

5 is a diagram illustrating a resonance condition due to a general thermal lens effect.

6 is a view showing a solid state laser for reducing the effect of the conventional thermal lens.

7 is a view showing a solid state laser cooling structure for reducing the thermal lens effect according to the present invention;

8 is a view showing a solid state laser cooling structure for reducing the thermal lens effect according to the present invention

Figure 9 is an exit portion of the solid state laser cooling structure to reduce the thermal lens effect according to the present invention

* Description of the symbols for the main parts of the drawings *

10: pumping laser diode 20: focusing optical system

30: reflector 40: laser medium

50: cooling window 60: metal mount

70: nonlinear material 80: output coupler

According to the structural features of the present invention for achieving the above object, a reflection mirror for changing the optical path of the focused light, a laser medium for generating a resonant wavelength of the light is changed, the cooling window for cooling the laser medium, And a metal mount for fixing the laser medium and the cooling window, and an output coupler for forming a resonance structure with the laser medium.

Preferably, the front surface of the laser medium is bonded to the cooling window, and the back side or the periphery is surrounded by the metal mount.

The material of the reflector is sapphire having excellent heat transfer rate, and the presence, location, and angle of the reflector are changed to allow the pumping light to be incident at an arbitrary angle. Is surrounded by the metal mount.

In addition, the laser medium and the metal mount are bonded using thermal adhesive, and the output light emitted to the output coupler changes the output position by changing the coating of the reflector, the cooling window, and the laser medium.

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

7 is a view showing a solid state laser cooling structure for reducing the thermal lens effect according to the present invention.

Referring to FIG. 7, a pumping laser diode 10, which is a pumping source arranged at least one, a focusing optical system 20 for focusing light of the at least one pumping laser diode, and an optical path of the focused light is changed. A reflector 30, a laser medium 40 receiving the pumped light to generate a resonant wavelength, a cooling window 50 cooling the laser medium in front of the laser medium 40, and the cooling window 50. ) And a metal mount 60, a nonlinear material 70, and an output coupler 80 that absorb heat of the cooling window 50 and the laser medium 40, while fixing the laser medium.

The reflector is a high reflection coating for pumping light (eg, 808 nm), an anti-reflection coating for resonance light (eg, 1064 nm / 914 nm), and the material has a heat transfer rate. Sapphire etc. which are a big optical substance can be used.

The cooling window 50 is an anti-reflection coating for pumping light (eg, 808 nm), and a resonance light (eg, 1064 nm / 914 nm) is also an anti-reflection coating.

In addition, a material of the cooling window 50 uses sapphire, which is an optical material having a high heat transfer rate, and a peripheral part is connected to the metal mount 60 to transmit heat.

In addition, the front surface of the laser medium 40 is bonded to the cooling window 50 and is bonded to the rear surface or the metal mount 60 surrounding the periphery using a thermal adhesive having excellent heat transfer. The front side is anti-reflection coating for resonant light, and the back side is high reflection coating for resonant light.

In addition, the material of the metal mount 60 uses a copper (copper) having a large heat transfer rate.

Referring to the operation method of the solid state laser cooling device of the above structure is as follows.

When the pumping laser diode 10 which is the pumping source emits pumping light, the focusing lens 20 focuses the emitted pumping light. In this case, in order to focus the focused pumping light on the laser medium 40, the pump 30 converts the pumping light toward the laser medium 40.

Accordingly, the focused pumping light is redirected by the reflector 30 to the laser medium 40, and the pumping light passes through the cooling window 50 that cools the laser medium 40. The heat of this pumping light is then transferred to the metal mount 60 which is connected to the periphery.

In this case, resonant light is generated in the laser medium 40, and heat generated by the pumping light in the laser medium 40 is quickly transferred to the metal mount 60.

A cooling fan (FAN) or a TE element is attached to the metal mount 60 to cool the heat generated continuously.

The resonant light generated by the laser medium 40 is reflected from the rear surface of the laser medium 40 and travels toward the output coupler 80.

Accordingly, the back side of the laser medium 40 and the output coupler 80 form a resonant structure, and the nonlinear material 70 is oscillated with visible light by generating Second Harmonic Generation (SHG).

8 is a view showing an incident portion of a solid state laser cooling structure pumping source for reducing the thermal lens effect according to the present invention.

Referring to FIG. 8, the presence, position, and angle of the reflector 30 may be changed by allowing the pumped light to be incident at an angle other than 90 deg.

9 is a view showing the position change of the exit portion of the solid state laser cooling structure to reduce the thermal lens effect according to the present invention.

Referring to FIG. 9, the output position may be changed by changing the coating in the reflector 30, the cooling window 50, and the laser medium 40 with respect to the output light (eg, 532 nm / 457 nm).

As described above, the present invention has the effect of realizing a small high power laser, which could not be implemented due to the problem of the conventional thermal lens.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the examples, but should be defined by the claims.

Claims (6)

A reflector for changing an optical path of focused light; A laser medium for generating a resonant wavelength of the changed light path; A cooling window for cooling the laser medium; A metal mount fixing the laser medium and the cooling window; And an output coupler forming a resonant structure with the laser medium. The method of claim 1, Solid state cooling device, characterized in that the pumping light is incident at an arbitrary angle by changing the presence, location and angle of the reflector. The method of claim 2, The material of the reflector is a solid-state laser cooling device, characterized in that the heat transfer rate is excellent sapphire The method of claim 1, The laser medium is solid-state laser cooling device, characterized in that the front surface is bonded to the cooling window, the back or peripheral is surrounded by the metal mount. The method of claim 3, wherein The laser medium and the metal mount is a solid laser cooling apparatus characterized in that the bonding using a thermal adhesive (Thermal Adhesive) The method of claim 1, And output light emitted from the output coupler to the output position by changing the reflector, the cooling window, and the coating of the laser medium.