KR20160053799A

KR20160053799A - Laser system

Info

Publication number: KR20160053799A
Application number: KR1020150153344A
Authority: KR
Inventors: 김지원; 김동준
Original assignee: 한양대학교 에리카산학협력단
Priority date: 2014-10-31
Filing date: 2015-11-02
Publication date: 2016-05-13
Also published as: KR101747906B1

Abstract

The present invention relates to a laser system. The laser system according to the present embodiment includes: a pumping part for generating a pumping beam; a first resonator having a gain material that generates light by the pumping beam, and generating a first laser beam by resonating first light from the light generated from the gain material in a first light path; and a second resonator for generating a second laser beam by resonating second light from the light generated from the gain material by the pumping beam in a second light path. According to an embodiment of the present invention, a spatial mode of the laser beam (for example, fundamental Gaussian mode, Laguerre-Gaussian mode and a multi-mode that is a combination of the modes) is able to be controlled in various manners by using inexpensive optical equipment, and a high power laser beam is able to be generated by using a laser system having a simple structure.

Description

Laser system {LASER SYSTEM}

The present invention relates to a laser system, and more particularly, to a laser system capable of adjusting a spatial mode of a laser beam.

1 is a configuration diagram of a conventional solid state laser system. 1, the beam output from the diode laser 10 for a pump is made into a suitable beam shape by an optical fiber junction or lenses 20 and 30, and then a laser material 50, to which a rare earth material is added, Or pumped laterally. A Fabry-Perot resonator consisting of a high-reflection mirror 40, a partial reflection mirror 70 and a lens 60 is configured to form a laser beam from the laser material 50 by pumping do.

The spatial cross-sectional shape of the laser beam output from the resonator is determined by a spatial shape that resonates in the resonator, that is, a transverse mode. The spatial mode has a Hermite-Gaussian (HG) mode, commonly referred to as a TEM mode, and a Laguerre-Gaussian (LG) mode, referred to as a donut mode. The type of spatial mode oscillation from the laser is determined by the pumping beam and the resonator conditions. Since the beam characteristic of the laser beam is superior to that of the higher order mode in the case of the low order mode, it is necessary to oscillate the TEM00 mode of the low order mode called the fundamental Gaussian mode when the beam characteristic is important. In contrast, the primary mode (LG01) of the Laguerre-Gaussian mode has a specific intensity distribution of donut or ring shape with a beam center intensity of zero, and is capable of capturing and controlling fine nanoparticles, a high resolution image microscope, And so on.

Since each spatial mode has various application fields according to its shape, it is obvious that it is very useful if it is possible to freely convert between different spatial modes. However, in one laser system, two kinds of spatial modes It is not easy to oscillate at the same time. A typical known method for oscillating two kinds of spatial modes in one laser system is largely a method using a thermal lens and a method of adjusting a pumping beam.

In the case of a laser system using a thermal lens, the TEM00 mode, which is the fundamental mode, oscillates at a low output power of a small output beam intensity. However, if the intensity of the pumping beam is increased, The LG01 mode will oscillate. However, this method changes the spatial mode depending on the output of the beam, and can not obtain two spatial modes simultaneously under the same laser output. Also, since the heat lens effect is very sensitive to resonance conditions such as resonator length, it is very difficult to obtain a stable operating condition of the LG01 mode, which is a high power mode.

The pumping beam is controlled by independently applying a pumping beam for oscillating the TEM00 mode and a ring-shaped pumping beam for oscillating the LG01 mode, and obtaining a desired laser beam by varying pumping conditions as required. However, this method is disadvantageous in that, in order to obtain a ring-shaped pumping beam, a general diode pumping beam must be formed by passing through a special optical element such as a special optical fiber having a hollow center. In another method, a computer-adjustable spatial phase adjuster is inserted in the resonator to directly adjust the phase and loss of the entire resonance mode section to obtain a desired shaped beam. In this case, however, the manufacturing cost of the laser system is greatly increased, for example, the spatial phase adjuster used reaches tens of millions of Won, and there is a problem that it can not withstand high output due to the material characteristics of the used optical device.

It is an object of the present invention to provide a laser system capable of variously adjusting a spatial mode of a laser beam (for example, a fundamental Gaussian mode, a Laguerre-Gaussian mode, and a multimode in which these modes are mixed).

Another object of the present invention is to provide a laser system capable of generating a laser beam having various beam shapes by an inexpensive optical apparatus and generating a high output laser beam.

The problems to be solved by the present invention are not limited to the above-mentioned problems. Other technical subjects not mentioned will be apparent to those skilled in the art from the description below.

A laser system according to an aspect of the present invention includes: a pumping unit for generating a pumping beam; A first resonator including a gain material that generates light by the pumping beam, the first resonator generating a first laser beam by resonating first light in the light generated in the gain material in a first optical path; And a second resonator for generating a second laser beam by resonating the second light in the light generated in the gain material by the pumping beam in a second optical path.

The second resonator may have a laser oscillation threshold value smaller than that of the first resonator.

Wherein the first resonator comprises: a first reflector, disposed between the pumping portion and the gain material, for reflecting the first light to the first optical path at one end of the first optical path; And a second reflector reflecting the first light to the first optical path at the other end of the first optical path.

Wherein the first light comprises a first polarized beam of light emerging from the gain material and the second light comprises a second polarized beam orthogonal to the first polarized beam of light, And a polarizer provided between the second reflector and providing the first polarized beam to the first optical path and providing the second polarized beam to the second optical path.

And a stop provided between the polarizer and the second reflector.

The laser system may oscillate the first laser beam in a different spatial mode depending on the aperture size of the aperture.

The spatial mode may include a fundamental Gaussian mode, a Laguerre-Gaussian mode, and a multi-mode in which the fundamental Gaussian mode and the Laguerre-Gaussian mode are mixed.

Wherein the second resonator comprises: a gain material shared by the first resonator; The first reflector being shared with the first resonator and reflecting the second polarized beam to the polarizer at one end of the second optical path; And a third reflector for reflecting the second polarized beam from the other end of the second optical path to the second optical path.

The third reflector may have a reflectance higher than that of the second reflector.

The laser system may further include: a first lens unit disposed between the polarizer and the second mirror; And a second lens unit disposed between the polarizer and the third reflector, wherein a focal length of the first lens unit and the second lens unit is set so that the first resonator and the second resonator have different laser oscillation conditions .

The laser system may further include a diaphragm provided between the polarizer and the third reflector.

The diaphragm may block the oscillation of a laser-Gaussian mode laser beam having a donut-shaped spatial intensity distribution.

Wherein the laser system is disposed in at least one of the polarizer and the second reflector, and between the polarizer and the third reflector, and wherein the optical system adjusts the loss of at least one of the first laser beam and the second laser beam As shown in FIG.

The optical element may include at least one of an acoustooptic regulator, an electro-optic regulator, and a micro-adjustment diaphragm.

The pumping unit may generate a pumping beam of a larger size than the laser beam of the fundamental Gaussian mode.

According to another aspect of the present invention, there is provided a pumping apparatus including: a pumping unit generating a pumping beam; A gain material that generates light by the pumping beam; A first reflector disposed between the pumping portion and the gain material and transmitting the pumping beam toward the gain material; A polarizer for providing a first polarized beam of light emerging from the gain material to a first optical path and providing a second polarized beam of light to a second optical path; A second reflector provided at an end of the first optical path for reflecting the first polarized beam to the polarizer; And a third reflector, disposed at an end of the second optical path, for reflecting the second polarized beam to the polarizer.

The laser system may further include a first stop provided between the polarizer and the third reflector.

The laser system may further include a second stop provided between the polarizer and the second reflector.

Wherein the laser system further comprises an optical element provided in at least one of the polarizer and the second reflector, and between the polarizer and the third reflector, wherein the optical element is arranged between the first reflector and the second reflector, And a second laser beam that is resonated in a second optical path between the first reflector and the third reflector.

According to the embodiment of the present invention, spatial modes of the laser beam (e.g., fundamental Gaussian mode, Lagrange-Gaussian mode, multi-mode in which these modes are mixed) can be variously adjusted.

Further, according to the embodiment of the present invention, a laser beam having various beam shapes can be generated by a low-cost optical mechanism, and a high output laser beam can be generated by a laser system of simple structure.

The effects of the present invention are not limited to the effects described above. Unless stated, the effects will be apparent to those skilled in the art from the description and the accompanying drawings.

1 is a configuration diagram of a conventional solid state laser system.
2 is a configuration diagram of a laser system 100 according to an embodiment of the present invention.
3 is a configuration diagram of a laser system 100 according to another embodiment of the present invention.
FIG. 4 is an image showing a laser-Gaussian mode laser beam generated by the laser system 100 according to the embodiment of FIG.
5 is an image showing a multiple spatial mode laser beam generated by the laser system 100 according to the embodiment of FIG.
FIG. 6 is an image showing the fundamental Gaussian mode laser beam generated by the laser system 100 according to the embodiment of FIG.
FIG. 7 is a graph showing a spatial intensity distribution of a laser beam generated by the laser system 100 according to an embodiment of the present invention, in spatial mode.
8 is a configuration diagram of a laser system 100 according to another embodiment of the present invention.
9A to 9D are images showing various laser beams of various spatial modes generated according to the embodiment of FIG.

Other advantages and features of the present invention and methods of achieving them will be apparent by referring to the embodiments described hereinafter in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and the present invention is only defined by the scope of the claims. Although not defined, all terms (including technical or scientific terms) used herein have the same meaning as commonly accepted by the generic art in the prior art to which this invention belongs. A general description of known configurations may be omitted so as not to obscure the gist of the present invention. In the drawings of the present invention, the same reference numerals are used as many as possible for the same or corresponding configurations. To facilitate understanding of the present invention, some configurations in the figures may be shown somewhat exaggerated or reduced.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises", "having", or "having" are intended to specify the presence of stated features, integers, steps, operations, components, Steps, operations, elements, parts, or combinations thereof, whether or not explicitly described or implied by the accompanying claims.

The laser system according to the embodiment of the present invention is characterized in that the first light (first polarized light beam) and the second light (second polarized light beam) of the light generated in the gain material (laser material) And includes a first resonator (main resonator) and a second resonator (auxiliary resonator) for generating a first laser beam and a second laser beam by resonance. In the laser system according to this embodiment, the second resonator is configured to share a gain material with the first resonator, and the spatial gain distribution of the gain material is controlled by the second resonator, whereby the first laser oscillating in the first resonator The spatial mode of the beam is adjusted.

The fundamental Gaussian mode (low-order space mode) first oscillates in the second resonator (that is, the resonator having a low laser oscillation threshold value) in which the gain ratio of the gain material reaches the laser oscillation threshold value of the first resonator and the second resonator. Since the spatial gain factor inside the gain material is limited by the spatial mode that starts oscillating first, the center gain gain of the gain material is limited by the low-order space mode oscillated in the second resonator. Accordingly, in the other resonator (first resonator) having a high laser oscillation threshold value, the gain ratio of the low-order space mode does not exceed the laser oscillation threshold value, and in the first resonator, It oscillates from a higher spatial mode with a spatial intensity distribution.

According to this embodiment, the spatial gain distribution of the gain material is actively controlled by using a simple optical element such as diaphragm, acoustic or electro-optical element inserted in the first resonator or the second resonator, Gaussian mode (LG01) with a donut-shaped spatial intensity distribution (LG01), a multi-mode with mixed modes of these modes A laser beam can be selectively obtained.

Also, according to the present embodiment, it is possible to obtain a laser output beam having an arbitrary spatial intensity distribution by inserting an optical element (an acousto-optic controller, an electro-optical controller, a fine adjustment diaphragm or the like) capable of arbitrarily mixing different spatial modes in a resonator have. Further, according to the embodiment of the present invention, a laser beam having various beam shapes can be generated by a low-cost optical mechanism, and a high output laser beam can be generated by a laser system of simple structure.

2 is a configuration diagram of a laser system 100 according to an embodiment of the present invention. 2, a laser system 100 according to an exemplary embodiment of the present invention includes a pumping unit P, a first resonator MR (main resonator), a second resonator AR (auxiliary resonator), a polarizer 180 and a first diaphragm 200. The pumping portion P generates a pumping beam for pumping the gain material 150. In one embodiment, the pumping portion P may include a diode pumping source 110 and optical lens portions 120 and 130. In one example, the diode pumping source 110 may be provided with a diode laser that outputs a beam having a particular wavelength (e.g., 808 nm).

The beam generated by the diode pumping source 110 may be provided to the optical lens units 120 and 130 through an optical fiber. The beam generated by the diode pumping source 110 is transformed by the optical lens units 120 and 130 into a pumping beam having a magnitude suited to the laser oscillation conditions of the first resonator MR and the second resonator AR, (150). The pumping beam may be provided in a size that can oscillate both in a low spatial mode (e.g., a fundamental Gaussian mode) and a high spatial mode (e.g., a Laguerre-Gaussian mode).

The first resonator MR may include a first reflector 140, a second reflector 170, a gain material 150, and a first lens unit 160. In one embodiment, the first resonator MR is configured to pump first light (e.g., a first polarized beam polarized by the polarizer 180) of light generated in the gain material 150 by pumping to a first reflector 140 and the second reflector 170 in the first optical path LP1, LP2. Accordingly, a first laser beam oscillating in the first resonator (MR) can be generated.

The first reflector 140 may be installed between the pumping portion P and the gain material 150. The first reflector 140 transmits the pumping beam provided from the pump unit P at one end of the first optical paths LP1 and LP2 and provides the pumping beam to the gain material 150. In the first optical path LP1 and LP2, And reflects the first polarized beam to the first optical path (LP1, LP2) so that the first polarized beam is resonated to oscillate the first laser beam. The first reflector 140 may be provided as a high reflectance mirror. For example, the first reflector 140 transmits a light having a wavelength (e.g., 808 nm) corresponding to the pumping beam at a high transmittance (e.g., a reflectance of 95% or more) , 1064 nm) can be reflected with a high reflectance (for example, a reflectance of 99.8% or more).

The second reflector 170 may reflect the first polarized beam from the other end of the first optical paths LP1 and LP2 to the first optical paths LP1 and LP2. The second reflector 170 may be provided as a partially transmissive mirror. The second reflector 170 may be provided as an output mirror that transmits a part of the first laser beam that resonates in the first optical paths LP1 and LP2. For example, the second reflector 170 reflects light of a wavelength (e.g., 1064 nm) corresponding to the first polarized beam with a first reflectance (e.g., 80% reflectance) The first laser beam can be transmitted at, for example, 20% transmittance.

The gain material 150 receives the pumping beam provided by the pump unit 110 and is pumped by the pumping beam to generate light. For example, the gain material 150 may be provided with a rare earth doped gain material (e.g., Nd: YAG), but if it is pumped by the pumping beam to generate light, It is not limited. In one example, the gain material 150 may be provided as a solid laser material, but is not limited thereto, and may be provided with other laser materials.

The polarizer 180 is installed between the gain material 150 and the second reflector 170. The polarizer 180 splits the light generated in the gain material 150 by pumping into a first polarized beam and a second polarized beam. Polarizer 180 provides a first polarized beam of light generated in gain material 150 to first optical paths LP1 and LP2 and provides a first polarized beam of light that is orthogonal to the first polarized beam of light generated in the gain material 150 And provide the second polarized beam to the second optical path (LP1, LP3) of the second resonator (AR). In one example, the polarizer 180 may transmit the first polarized beam and reflect the second polarized beam. As another example, the polarizer 180 may be provided to reflect the first polarized beam and transmit the second polarized beam. The first polarized light beam oscillates in the first optical paths LP1 and LP2 and the second polarized light beam oscillates in the second optical paths LP1 and LP3 by the polarizer 180. [

The first lens unit 160 may be installed between the polarizer 180 and the second reflector 170. The laser oscillation condition of the first resonator (MR) may be changed by the first lens unit (160). The size of the fundamental Gaussian mode laser beam of the first resonator MR can be changed according to the focal length and position of the first lens unit 160. [ In an embodiment, the first lens unit 160 may be provided as a plano-convex lens.

The second resonator AR may be provided to adjust the shape (spatial mode) of the first laser beam oscillated in the first resonator MR. A second resonator (AR) is coupled to the first resonator (MR) to share a gain material (150) with the first resonator (MR). The second resonator AR operates independently through the second optical path LP1 and LP3 different from the first resonator MR using polarization or the like to oscillate the second polarized beam, Adjust the laser gain distribution. The second resonator AR resonates the second polarized light beam, which is orthogonal to the first polarized beam of light generated in the gain material 150 by pumping, in the second optical path LP1 and LP3, Beam can be generated.

The second resonator AR includes a first reflector 140, a third reflector 210, a gain material 150, and a second lens unit 190. The second resonator AR is configured to share the gain material 150 and the first reflector 140 with the first resonator MR. The first reflector 140 reflects the second polarized beam from one end of the second optical path LP1 or LP3 to the second optical path LP2 so that the second polarized beam is resonant in the second optical paths LP1 and LP3 to oscillate the second laser beam. The light can be reflected to the light guide 180. For example, the first reflector 140 may reflect light having a wavelength (e.g., 1064 nm) corresponding to the second polarized beam at a high reflectivity (e.g., a reflectance of 99.8% or more).

The third reflector 210 may reflect the second polarized beam from the other end of the second optical paths LP1 and LP3 to the second optical paths LP1 and LP3. The third reflector 210 may be provided as a partially transmissive mirror. The third reflector 210 may be provided as an output mirror that transmits a part of the second laser beam resonating in the second optical paths LP1 and LP3. For example, the third reflector 210 reflects light of a wavelength (e.g., 1064 nm) corresponding to the second polarized beam at a second reflectance (e.g., 95% reflectance) The second laser beam can be transmitted at, for example, 5% transmittance.

The first resonator MR and the second resonator AR may be set to have different laser oscillation conditions (e.g., laser oscillation threshold values). For this, the third reflector 210 may have a different reflectance than the second reflector 170. In one embodiment, the third reflector 210 is provided with an output mirror having a reflectivity higher than that of the second mirror 170, in order to allow the lower resonance mode to oscillate in the second resonator AR before the first resonator MR. .

The second lens unit 190 may be installed between the polarizer 180 and the third reflector 210. The laser oscillation condition of the second resonator (AR) may be changed by the second lens unit (190). The size of the fundamental Gaussian mode laser beam of the second resonator AR may be changed according to the focal length and position of the second lens unit 190. [ In one embodiment, the second lens unit 190 may be provided as a plano-convex lens.

The first diaphragm 200 may be provided on the optical path LP3 between the polarizer 180 and the third reflector 210. [ The first diaphragm 200 may be provided with an adjustable aperture size. In order to adjust the spatial gain distribution of the gain material 150 and adjust the spatial shape of the first laser beam oscillating in the first resonator MR, the first diaphragm 200 is arranged in the second resonator (AR) 2 Gaussian mode laser beam having a high spatial mode of the laser beam, for example, a donut-like spatial intensity distribution.

The operation principle of the laser system according to the above embodiment will be described as follows. The energy absorbed by the gain material 150 by pumping raises the laser doping ions of the low energy level to a high energy level and the number of laser doping ions that are present at the high energy level in the gain material 150 gradually increases . Accordingly, energy is gradually accumulated in the gain material 150 in proportion to the number of upper laser level ions, and the laser amplification gain is gradually increased. The second laser beam is oscillated in the second resonator AR when the gain factor value of the gain material 150 reaches a condition equal to or larger than a threshold value that is larger than the loss inside the second resonator AR.

In each resonator (MR, AR), the laser oscillation threshold depends on the resonator structure, the overlap efficiency between the pumping beam and the laser beam mode, and the resonator loss including the partially transmissive reflector. In an embodiment, when the output mirror (the second reflector) 170 having a low reflectance is provided in the first resonator MR and the output mirror (the third reflector) 210 having a high reflectance is provided in the second resonator AR, The second resonator AR has a lower laser oscillation threshold value than the first resonator MR.

Therefore, when the gain material 150 is pumped, the laser oscillation threshold value of the fundamental Gaussian mode in the second resonator AR is lower than that of the first resonator MR. Therefore, in the second resonator MR, The gain of the gain material 150 exceeds the threshold value and the second laser beam oscillates. The upper energy level doped ion number within the gain material 150 that coincides with the spatial mode of the second laser beam that has started oscillating in the second resonator MR does not increase anymore even though the intensity of the pumping beam is greater, . Therefore, the first Gaussian mode can not oscillate in the first resonator (MR) even if the output becomes high. That is, since the shape of the first laser beam in the first resonator MR is limited by the spatial mode in which the spatial gain rate in the gain material 150 starts to oscillate first, It is possible to adjust the spatial intensity distribution of the laser beam.

More specifically, the shape of the pumping beam has a Gaussian or a hat-top with the highest intensity at the center of the beam, and the lower the laser mode, the lower the threshold value, so that it begins to oscillate first. If the pumping beam corresponding to the fundamental Gaussian mode (TEM00) and the Laguerre-Gaussian mode (LG01, etc.) is applied while the first diaphragm 200 is opened, the spatial mode of the laser beam oscillated in the second resonator Mode mode in which the fundamental Gaussian mode (TEM00) and the first-order Laguerre-Gaussian mode (LG01) coexist.

If the aperture size of the first diaphragm 200 is set so as not to block the fundamental Gaussian mode (TEM00) laser beam in the second resonator AR and to block the donut-shaped first laser-Gaussian mode (LG01) The gain distribution of the central portion of the gain material 150 is shifted to the resonance frequency of the second resonator AR2 as the laser beam oscillates in the fundamental Gaussian mode TEM00, ) By the spatial mode that oscillates in the second direction.

At this time, if the pumping is continued to the gain material 150, the gain ratio is not fixed to the oscillation threshold value at a position (center portion) coinciding with the shape of the fundamental Gaussian mode in the gain material 150, Gaussian mode (for example, LG01 mode) in which the beam gain is relatively large and the shape is different from that of the fundamental Gaussian mode (n is an integer of 1 or more) The gain rate of the pump increases continuously with the pumping output.

Accordingly, in the first resonator (MR), the ring-shaped higher-order mode, which differs greatly in shape from the fundamental Gaussian mode, can have a pumping value exceeding a threshold value. In the first resonator (MR), a fundamental Gaussian mode But the laser beam of the first-order Lager-Gaussian mode (LG01) having a donut-shaped spatial distribution is oscillated. When the diameter of the first diaphragm 200 inserted in the second resonator AR is regulated to prevent the oscillation of the higher spatial mode in the second resonator AR, the second resonator AR is operated in the fundamental Gaussian mode And the gain distribution of the gain material 150 has a ring shape.

If the pumping beam is pumped to the gain material 150 at a size larger than the fundamental Gaussian mode laser beam with the first diaphragm 200 fully closed to prevent the laser from oscillating in the second resonator AR, In the resonator MR, a multi-mode laser beam is generated in which the high-order modes such as the fundamental Gaussian mode (TEM00) and the first-order Lager-Gaussian mode (LG01) oscillate simultaneously.

3 is a configuration diagram of a laser system 100 according to another embodiment of the present invention. In the description of the embodiment of FIG. 3, the same elements as those of the embodiment of FIG. 2 or the corresponding elements may be omitted. The laser system 100 according to the embodiment of FIG. 3 differs from the embodiment of FIG. 2 in that the second diaphragm 220 is provided in the first resonator MR. The second aperture stop 220 may be installed in the first optical path LP2 between the polarizer 180 and the second reflector 170. [ The second diaphragm 220 can adjust the shape of the first laser beam oscillated in the first resonator MR. For example, the second diaphragm 220 may block the higher order mode beam depending on the aperture size.

FIG. 4 is an image showing a laser-Gaussian mode laser beam generated by the laser system 100 according to the embodiment of FIG. 5 is an image showing a multiple spatial mode laser beam generated by the laser system 100 according to the embodiment of FIG. FIG. 6 is an image showing the fundamental Gaussian mode laser beam generated by the laser system 100 according to the embodiment of FIG. FIG. 7 is a graph showing a spatial intensity distribution of a laser beam generated by the laser system 100 according to an embodiment of the present invention, in spatial mode.

Referring to FIGS. 3-7, as described in the embodiment of FIG. 2, the first diaphragm 200 is partially closed to block the high spatial mode at the second resonator AR to pumping the gain material 150 The first Gaussian mode TEM00 oscillates in the second resonator AR and the first resonator MR oscillates in the higher order space of the Luger-Gaussian mode LG01 having a donut shape as shown in FIGS. Mode oscillates. In Fig. 7, the abscissa represents the displacement from the center of the laser beam, and the ordinate represents the value obtained by normalizing the intensity of the laser beam.

At this time, when the first diaphragm 200 is completely closed and the second diaphragm 220 is completely opened so as to prevent the laser from oscillating in the second resonator AR, A multimode laser beam is generated in which a high spatial spatial mode such as a primary Gaussian mode (TEM00) and a primary Laguer-Gaussian mode (LG01) oscillate simultaneously. The diameter of the second diaphragm 220 provided in the first resonator MR is regulated (partially opened) and the oscillation of the high-spatial-mode mode is performed by adjusting the diameter of the second diaphragm 220 installed in the first resonator MR, The first resonator MR oscillates in the fundamental Gaussian mode TEM00 having a large output at the central portion as shown in Figs. 6 and 7.

Therefore, according to the present embodiment, the opening and closing of the two diaphragms 200 and 220 inserted into the resonators MR and AR and the size of the opening are adjusted without changing the other conditions, MR) can be freely adjusted in the fundamental Gaussian mode (TEM00), the first-order Laguerre-Gaussian mode (LG01), or a mixed spatial mode in which they are mixed.

8 is a configuration diagram of a laser system 100 according to another embodiment of the present invention. FIGS. 9A to 9D are diagrams showing laser beams of various multiple spatial modes generated according to the embodiment of FIG. 8. FIG. In the following description of the embodiment of FIG. 8, the same or similar elements as those of the above-described embodiments may be omitted. The laser system according to the embodiment of FIG. 8 differs from the previously described embodiment in that an optical element 230 for adjusting the loss of the second laser beam is provided in the second resonator AR.

The optical element 230 is disposed between the first diaphragm 200 and the third reflector 210 but the optical element 230 may be disposed between the polarizer 180 and the second lens unit 190. The optical element 230 actively adjusts the intensity or loss (resonator loss) of the second laser beam to finely adjust the difference in the laser oscillation threshold value of the fundamental mode of the first resonator MR and the second resonator AR . In one embodiment, the optical element 230 may be provided as an acousto-optic modulator, an electro-optic modulator, or a micro-adjustment aperture capable of finely adjusting the aperture size.

If the difference between the laser oscillation threshold values of the first resonator MR and the second resonator AR is finely adjusted by the optical element 230, even if the fundamental Gaussian mode oscillates in the second resonator AR, ) Can cause the underlying Gaussian mode to oscillate. At this time, the ratio of the intensities of the fundamental Gaussian mode and the lagger-Gaussian mode of the laser beam oscillated in the first resonator (MR) is determined by the difference of the laser oscillation threshold values of the two resonators (MR, AR). 9A to 9D, a beam shape in which the fundamental Gaussian mode (TEM00) and the first-order Laguerre-Gaussian mode (LG01) are mixed at a desired ratio is generated in the first resonator MR by the optical element 230 .

The laser beam having a proper ratio of the two spatial modes is advantageously amplified at a high output through an output amplifier which is not shown. In other words, the amplification factor of the laser beam increases as the intensity of light increases. In the Gaussian beam, the center output is the highest, so that the amplification in the middle portion becomes larger and the amplification rate becomes smaller as the end becomes smaller. It will fall out. In addition, the intensity of the center portion increases too quickly, causing damage to the laser crystal before amplifying sufficient energy.

However, according to the present embodiment, in the case of a laser beam in which the fundamental Gaussian mode (TEM00) and the Laguer-Gaussian mode (LG01) are mixed at a desired ratio and the spatial distribution is appropriately made, And the intensity of the amplified beam is spatially uniform so that more energy can be obtained until damage due to high light intensity occurs.

8, the optical element 230 is inserted into the second resonator AR, but in another embodiment, the optical element 230 may be coupled to the first resonator MR, i.e., the polarizer 180, It is also possible to adjust the difference between the laser oscillation threshold values of the first resonator MR and the second resonator AR by adjusting the intensity or loss (first resonator loss) of the first laser beam by inserting it between the first resonator MR and the second resonator 170 Do.

The oscillation mode of the first resonator MR is controlled to oscillate to the n-th order higher-order mode, and the first diaphragm (220) is controlled to oscillate in the second resonator (AR) in the first Gaussian mode and the first Lager- It is also possible to cause only the n-th order Lagrange-Gaussian mode to be oscillated in the first resonator AR by making all of the spatial modes of the (n-1) -th order or less to be oscillated. Although not shown, it is also possible to control the spatial characteristics, temporal characteristics, and output characteristics of the laser beam by inserting another optical device (for example, Q-switch or the like) into the resonator.

As described above, according to this embodiment, the spatial gain distribution of the gain material is actively controlled by using a simple optical element such as diaphragm, acoustic or electro-optical element in the resonator, Simple and freely adjustable, the spatial mode of the laser beam can be divided into a fundamental Gaussian mode (TEM00) with a high center output, a Laguerre-Gaussian mode with a donut-shaped spatial intensity distribution (LG01) It can be adjusted freely.

Also, according to the present embodiment, by increasing the size of the pumping beam and the aperture of the first diaphragm 200 inserted in the second resonator AR to a size corresponding to the (n-1) -th spatial mode, It is possible to easily generate the n-th order Laguerre-Gaussian mode from the first resonator MR. Further, according to this embodiment, it is possible to freely select the spatial mode (beam shape) of the laser beam by using a simple laser system using low-cost optical instruments (aperture, polarizer, reflector) have.

Further, according to this embodiment, by inserting an optical element (for example, an acousto-optic modulator or the like) capable of adjusting the resonator loss in the resonator and arbitrarily mixing beams of different spatial modes, the fundamental Gaussian mode and the first- A laser output beam having an arbitrary spatial intensity distribution in which the mode is mixed at a desired ratio can be obtained. In addition, when a laser beam having an appropriate spatial intensity distribution is incident on a high output laser amplifier, not only the amplification rate of the beam can be made uniform spatially, but also the intensity of the amplified beam is spatially uniform, It is possible to obtain more energy until the damage caused by the laser beam is generated. Thus, a high-output laser beam can be generated by a simple structure laser system. Also, optical elements such as spatial phase adjusters can not be used for high power laser operation due to the very low laser damage threshold due to the nature of the materials used, but the optical components used in this embodiment have very high laser damage thresholds, There is no.

It is to be understood that the above-described embodiments are provided to facilitate understanding of the present invention, and do not limit the scope of the present invention, and it is to be understood that various modifications are possible within the scope of the present invention. It is to be understood that the technical scope of the present invention should be determined by the technical idea of the claims and the technical scope of protection of the present invention is not limited to the literary description of the claims, To the invention of the invention.

P: Pumping section
MR: first resonator
AR: second resonator
LP1, LP2: the first light path
LP1, LP3: Second optical path
110: Diode pumping source
120, 130: Optical lens
140: first reflector
150: Gain material
160: first lens unit
170: second reflector
180: Polarizer
190: second lens portion
200: 1st aperture
220: Second stop
230: Optical element

Claims

A pumping unit generating a pumping beam;
A first resonator including a gain material that generates light by the pumping beam, the first resonator generating a first laser beam by resonating first light in the light generated in the gain material in a first optical path; And
And a second resonator for generating a second laser beam by resonating the second light in the light generated in the gain material by the pumping beam in a second optical path.

The method according to claim 1,
Wherein the second resonator has a laser oscillation threshold value that is less than the first resonator.

The method according to claim 1,
Wherein the first resonator comprises:
A first reflector, disposed between the pumping unit and the gain material, for reflecting the first light to the first optical path at one end of the first optical path; And
And a second reflector for reflecting the first light to the first optical path at the other end of the first optical path.

The method of claim 3,
Wherein the first light comprises a first polarized beam of light emerging from the gain material,
Wherein the second light comprises a second polarized beam that is orthogonal to the first polarized beam in the light,
A polarizer disposed between the gain material and the second reflector and providing the first polarized beam to the first optical path and providing the second polarized beam to the second optical path.

5. The method of claim 4,
And a diaphragm provided between the polarizer and the second reflector.

6. The method of claim 5,
Wherein the first laser beam of different spatial modes is oscillated according to the aperture size of the aperture.

The method according to claim 6,
Wherein the spatial mode includes a fundamental Gaussian mode, a Laguerre-Gaussian mode, and a multi-mode in which the fundamental Gaussian mode and the Laguerre-Gaussian mode are mixed.

5. The method of claim 4,
The second resonator includes:
The gain material being shared with the first resonator;
The first reflector being shared with the first resonator and reflecting the second polarized beam to the polarizer at one end of the second optical path; And
And a third reflector for reflecting the second polarized beam to the second optical path at the other end of the second optical path.

9. The method of claim 8,
And the third reflector has a higher reflectance than the second reflector.

9. The method of claim 8,
A first lens unit disposed between the polarizer and the second reflector; And
And a second lens unit provided between the polarizer and the third reflector,
Wherein the focal lengths of the first lens unit and the second lens unit are set so that the first resonator and the second resonator have different laser oscillation conditions.

9. The method of claim 8,
And a diaphragm provided between the polarizer and the third reflector.

12. The method of claim 11,
Wherein the diaphragm interrupts oscillation of a laser-Gaussian mode laser beam having a donut-like spatial intensity distribution.

9. The method of claim 8,
Further comprising an optical element provided in at least one of the polarizer and the second reflector and between the polarizer and the third reflector and adjusting the loss of at least one of the first laser beam and the second laser beam Laser system.

14. The method of claim 13,
Wherein the optical element comprises at least one of an acoustooptic regulator, an electro-optic regulator, and a micro-adjustment diaphragm.

The method according to claim 1,
Wherein the pumping section generates a pumping beam of a larger magnitude than the laser beam of the fundamental Gaussian mode.

A pumping unit generating a pumping beam;
A gain material that generates light by the pumping beam;
A first reflector disposed between the pumping portion and the gain material and transmitting the pumping beam toward the gain material;
A polarizer for providing a first polarized beam of light emerging from the gain material to a first optical path and providing a second polarized beam of light to a second optical path;
A second reflector provided at an end of the first optical path for reflecting the first polarized beam to the polarizer; And
And a third reflector disposed at an end of the second optical path and reflecting the second polarized beam to the polarizer.

17. The method of claim 16,
And a first diaphragm provided between the polarizer and the third reflector.

18. The method of claim 17,
And a second stop provided between the polarizer and the second reflector.

17. The method of claim 16,
Further comprising an optical element provided in at least one of between the polarizer and the second reflector, and between the polarizer and the third reflector,
Wherein the optical element includes a first laser beam resonating in a first optical path between the first reflector and the second reflector and a second laser beam resonating in a second optical path between the first reflector and the third reflector, A laser system for adjusting the loss of at least one of the beams.

20. The method of claim 19,
Wherein the optical element comprises at least one of an acoustooptic regulator, an electro-optic regulator, and a micro-adjustment diaphragm.