JP2009059924A - Laser generating device and laser machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To amplify an ultrashort pulse with a simple constitution in a laser generating device and a laser machining device. <P>SOLUTION: A cross-section area of a laser medium 23 orthogonal to an optical axis L of a seed light becomes larger from an incident side end part (a base end part) to an output side end part (a front edge part) corresponding to a beam power of the seed light gradually becoming larger as traveling through the laser medium 23 excited by an excitation light E. The amount of light of an excitation light E of an excitation light source 24 irradiating from the incident side end part to the output side end part of the laser medium 23 is configured to become larger corresponding to the cross-section area of the laser medium 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser generator capable of oscillating an ultrashort pulse and a laser processing apparatus.

  Some laser generators include an optical amplifier that amplifies seed light emitted from a seed light source (laser light having a wavelength that is actually desired) using a phenomenon called stimulated emission. The optical amplifier includes a laser medium made of a crystal doped with a light emitting element and an excitation light source that irradiates the laser medium with excitation light having a wavelength capable of exciting the light emitting element. In such a laser generator, a laser medium is irradiated with excitation light to excite a light emitting element in a high energy state, and seed light is incident on the laser medium. Then, the light emitting element in the laser medium emits laser light (stimulated emission) whose energy, phase, and traveling direction are aligned with the seed light, and the seed light is amplified while expanding the beam diameter in the laser medium. Propagated and emitted.

  However, in such a laser generator, the laser medium is damaged if the beam power exceeds the limit value of damage to the laser medium during the amplification propagation of the seed light in the laser medium. For this reason, it has been difficult to amplify laser light of an ultrashort pulse (for example, femtosecond pulse) in which the beam power is concentrated in a very short time width and becomes extremely strong.

Therefore, conventionally, a so-called chirp pulse amplification method (CPA method) is used as a method of amplifying ultrashort pulse light while suppressing damage to the laser medium (see, for example, Patent Document 1). In the CPA method, first, the pulse width of ultrashort pulse light as seed light is extended by a pulse stretcher, and then the laser light is amplified by a laser medium excited with a light emitting element. At this time, since the pulse width of the ultra-short pulse light is extended, the beam power of the amplified laser light can be suppressed, thereby reducing the burden on the laser medium. Thereafter, the pulse width of the amplified laser light is compressed by a pulse compressor to return to the original pulse width. As a result, the pulse width (beam power) increases as the pulse width becomes shorter, and as a result, an ultrahigh output, ultrashort pulse laser beam higher than the limit value of laser medium damage is obtained. In the CPA method, by amplifying the seed light through such a process, it is possible to amplify ultrashort pulse light while suppressing damage to the laser medium.
JP-T-2004-527001

  However, the laser generator as described above has a configuration because the light is amplified through a plurality of procedures using devices such as a pulse stretcher and a pulse compressor for expanding and contracting the pulse width of the ultrashort pulse light. As a result, it has become complicated, leading to an increase in the size and cost of the laser generator.

  The present invention has been made to solve the above problems, and an object of the present invention is to enable amplification of ultrashort pulse light with a simple configuration in a laser generator and a laser processing apparatus.

  In order to solve the above problems, the invention according to claim 1 comprises a laser medium made of a solid doped with a light emitting element and an excitation light source that excites the light emitting element by irradiating the laser medium with excitation light, An optical amplifier for amplifying the laser light emitted when the excited light emitting element returns from the excited state to the base state and emitting the amplified laser light from the tip of the laser medium; The medium is formed such that a cross-sectional area perpendicular to the optical axis of the emitted laser light increases from the base end portion to the tip end portion, and the excitation light source irradiates from the base end portion to the tip end portion of the laser medium. The gist of the invention is that the amount of the excitation light is configured to increase in accordance with the cross-sectional area of the laser medium.

  In the present invention, the laser medium has a cross-sectional area perpendicular to the optical axis of the emitted laser light, corresponding to the beam power of the laser light that gradually increases as it travels through the laser medium excited by the excitation light. It is formed so as to increase from the end to the tip. For this reason, the laser medium has a shape that can withstand the beam power of the laser light amplified over the entire optical axis direction, and as a result, the laser medium can be prevented from being damaged by the amplified laser light. . Further, since the laser medium is formed with a small cross-sectional area at the base end portion that does not require high durability, the laser medium can be efficiently reduced in size, thereby increasing the size of the laser generator. Can be suppressed. Furthermore, since the excitation light source is configured so that the amount of the excitation light irradiated from the base end portion to the tip end portion of the laser medium increases corresponding to the cross-sectional area of the laser medium, the laser medium is efficiently excited. Can be made. Accordingly, it is not necessary to use a device such as a pulse stretcher and a pulse compressor for expanding and contracting the pulse width of the laser light, and thus it is possible to amplify ultrashort pulse light with a simple configuration.

  According to a second aspect of the present invention, in the laser generator according to the first aspect, the excitation light source irradiates the excitation light from the distal end side to the proximal end side of the laser medium, and The gist thereof is that the amount of the excitation light irradiated from the base end portion to the tip end portion is provided so as to increase corresponding to the cross-sectional area of the laser medium.

  In the present invention, since the excitation light source is provided so as to irradiate the excitation light from the distal end side to the proximal end side of the laser medium, the light quantity of the excitation light received by the laser medium decreases as the proximal end portion away from the excitation light source. . Therefore, for example, even when only one excitation light source is used, the amount of excitation light irradiated from the base end portion to the tip end portion of the laser medium can be increased corresponding to the cross-sectional area of the laser medium. The number of parts can be reduced.

  According to a third aspect of the present invention, in the laser generator according to the first aspect, a plurality of the excitation light sources are provided, and the plurality of excitation light sources are in a direction orthogonal to an optical axis of laser light emitted from the laser medium. The gist of the present invention is to irradiate the excitation light with a light amount corresponding to the cross-sectional area of the laser medium.

  In the present invention, the plurality of excitation light sources are provided so as to irradiate each amount of excitation light according to the cross-sectional area from a direction orthogonal to the optical axis of the laser light emitted from the laser medium. Thereby, the light quantity of the said excitation light irradiated from the base end part of a laser medium to a front-end | tip part can be enlarged corresponding to the cross-sectional area of a laser medium.

  According to a fourth aspect of the present invention, in the laser generator according to any one of the first to fourth aspects, the laser medium includes a plurality of laser medium pieces arranged in parallel in the optical axis direction of the emitted laser light. The plurality of laser medium pieces are respectively formed such that the area of the incident surface of the laser medium piece arranged in the subsequent stage is larger than the area of the emission surface of the laser medium piece arranged in the previous stage. And

  In the present invention, the plurality of laser medium pieces are formed so that the area of the incident surface of the laser medium piece arranged in the subsequent stage is larger than the area of the emission surface of the laser medium piece arranged in the preceding stage. Laser light amplification using a medium piece can be performed. For example, when a crystal is used for the laser medium, the size of the crystal that can be formed is limited and the beam power that can be amplified is limited. Can be amplified.

  The invention according to claim 5 is the laser generator according to any one of claims 1 to 4, wherein the laser medium has a circular cross-sectional area perpendicular to the optical axis of the emitted laser light, The gist thereof is that a plurality of the excitation light sources are provided at equal intervals in the circumferential direction of the optical axis.

  In the present invention, since the laser medium has a circular cross-sectional area perpendicular to the optical axis of the emitted laser light, the beam spot of the laser light emitted from the laser medium can be made circular. In addition, since a plurality of excitation light sources are provided at equal intervals in the circumferential direction of the optical axis of the laser light emitted from the laser medium, the laser light can be amplified in a balanced manner.

  According to a sixth aspect of the present invention, in the laser generator according to any one of the first to fifth aspects, the seed light source for causing the light emitting element to emit seed light into the laser medium is used. The gist is prepared.

In the present invention, the laser beam can be emitted from the laser medium by the seed light emitted from the seed light source.
The gist of the invention described in claim 7 is that, in the laser processing apparatus, processing is performed on the object to be processed using the laser light emitted from the laser generator according to claims 1 to 6.

  In the present invention, it is possible to amplify ultrashort pulse light with a simple configuration in the laser generator, and thus contribute to simplification of the laser processing apparatus.

  Therefore, according to the above-described invention, it is possible to amplify ultrashort pulse light with a simple configuration in the laser generator and the laser processing apparatus.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
A laser processing apparatus 10 of the present embodiment whose schematic configuration is shown in FIG. 1 performs marking processing of characters, symbols, figures, and the like on the surface of a workpiece (processing object) W to be conveyed based on the control of the control unit 11. It is.

  The laser generator 12 of the laser processing apparatus 10 includes a seed light source 21 that can oscillate an ultrashort pulse laser beam as seed light, and an optical amplifier 22 that amplifies the seed light emitted from the seed light source 21 by stimulated emission. It is configured. The oscillation of the seed light source 21 is controlled by the control unit 11.

  The laser medium 23 provided in the rear stage of the seed light source 21 in the optical amplifier 22 is made of YAG (yttrium, aluminum, garnet) crystal doped with ytterbium (Yb) as a light emitting element, and seed light is incident on the inside thereof. It is installed to be. In FIG. 1, the shape of the laser medium 23 viewed from the side is illustrated. The laser medium 23 has a trapezoidal shape that spreads toward the front end side from which laser light is emitted in the side view and the plan view, and the incident-side end face and the emission-side end face on which the seed light is incident respectively have an optical axis L of the seed light. It is provided to be orthogonal. That is, the laser medium 23 has a rectangular cross section orthogonal to the optical axis L of the seed light, and the cross sectional area of the laser medium 23 from the incident side end (base end) where the seed light is incident to the emission side end (tip end). It is formed so as to increase in size. Further, the laser medium 23 has a symmetrical shape with respect to the optical axis L. The laser medium 23 has a length in the direction perpendicular to the paper surface of, for example, 100 μm or less at the incident side end surface, and the emission side end surface is formed to be 50 times or more the length of the incident side end surface.

  An excitation light source 24 that constitutes an optical amplifier 22 together with the laser medium 23 is provided obliquely above and obliquely below the emission side of the laser medium 23. In FIG. 1, they overlap in the direction perpendicular to the plane of the drawing, but a pair of pumping light sources 24 are arranged at predetermined intervals in the same direction. A total of four are provided corresponding to each corner.

  Each excitation light source 24 causes excitation light E having a wavelength capable of exciting ytterbium as a light emitting element to enter obliquely from the emission side to the incidence side of the laser medium 23, and the excitation light E is emitted from the laser medium 23. Irradiation is performed over the entire side end face and side face. Note that the oscillation of each excitation light source 24 is controlled by the control unit 11. Since the amount of the excitation light E emitted from each excitation light source 24 decreases as it travels through the laser medium 23, the light amount of the excitation light E received by the laser medium 23 decreases as the distance from the excitation light source 24 increases. That is, the amount of the excitation light E received by the laser medium 23 is the smallest at the incident side end and gradually increases toward the emission side end. By the irradiation with the excitation light E, the light emitting element in the laser medium 23 is excited to a high energy state. The energy absorbed by the laser medium 23 from the excitation light E increases from the incident side end to the emission side end. Further, since the excitation light source 24 irradiates the excitation light E so that the amount of light irradiated toward the tip side having a higher absorption rate is reduced because the cross-sectional area of the laser medium 23 is small, the laser light source 23 is efficient without waste. The excitation light E can be irradiated.

  When the seed light emitted from the seed light source 21 enters the laser medium 23 thus excited, the seed light is amplified and propagated in the laser medium 23 irradiated with the excitation light E from the excitation light source 24, and the laser medium. The beam power increases as it goes through 23. Since the laser medium 23 is formed so that the cross-sectional area perpendicular to the optical axis L of the seed light increases from the incident side end to the output side end, the seed light amplified over the entire optical axis L direction. It is shaped so that it can withstand the beam power, and as a result, it is not damaged by the amplified seed light. At this time, the seed light amplified and propagated in the laser medium 23 travels while expanding its beam diameter. The seed light thus amplified is emitted from the end face of the laser medium 23.

  In such an optical amplifier 22, since the laser medium 23 is formed with a small sectional area on the incident side that does not require high durability, the laser medium 23 can be efficiently downsized. In addition, the excitation light source 24 is provided so that the amount of excitation light E irradiated from the incident side end to the emission side end of the laser medium 23 increases corresponding to the cross-sectional area of the laser medium 23. The laser medium 23 can be excited efficiently. In such a laser generator 12, it is not necessary to use a device such as a pulse stretcher and a pulse compressor for expanding and contracting the pulse width of the seed light. Therefore, it is possible to amplify ultrashort pulse light with a simple configuration. .

  The laser light amplified and emitted by the laser medium 23 is converted into parallel light by the collimator lens 25 disposed at the subsequent stage of the laser medium 23, and the laser light is emitted from the laser generator 12.

  The galvanometer mirror 31 disposed at the rear stage of the laser generator 12 reflects the laser light emitted from the laser generator 12 and changes the irradiation direction thereof. For example, a pair of an X-axis mirror and a Y-axis It consists of a mirror. The galvanometer mirror 31 is angle-controlled by driving of the driving device 32 based on the control of the control unit 11 and scans the laser beam two-dimensionally based on characters, symbols, figures, etc. to be marked.

  A converging lens (fθ lens) 33 disposed at the subsequent stage of the galvanometer mirror 31 converges the laser light emitted from the laser generator 12 until the spot diameter reaches a predetermined spot on the surface of the workpiece W, whereby the laser light is marked. The energy density suitable for processing is increased. In this way, the marking process is performed on the surface of the workpiece W.

Next, characteristic effects of the present embodiment will be described.
(1) The laser medium 23 corresponds to the beam power of the seed light whose cross-sectional area perpendicular to the optical axis L of the seed light gradually increases as it travels through the laser medium 23 excited by the excitation light E. It is formed to increase from the incident side end (base end) to the emission side end (tip). Therefore, the laser medium 23 has a shape that can withstand the beam power of the seed light amplified over the entire optical axis L direction, and as a result, the laser medium 23 is prevented from being damaged by the amplified seed light. be able to. In addition, since the laser medium 23 is formed with a small sectional area on the incident side that does not require high durability, the laser medium 23 can be efficiently reduced in size, and as a result, the laser generator 12 is increased in size. Can be suppressed. Accordingly, it is not necessary to use a device such as a pulse stretcher and a pulse compressor for expanding and contracting the pulse width of the seed light, so that ultrashort pulse light can be amplified with a simple configuration.

  (2) The excitation light source 24 is configured so that the amount of the excitation light E irradiated from the incident side end portion to the emission side end portion of the laser medium 23 increases corresponding to the cross-sectional area of the laser medium 23. The laser medium 23 can be excited efficiently.

  (3) Since the excitation light E is radiated from the emission side to the incidence side of the laser medium 23, the amount of the excitation light E received by the laser medium 23 is smaller at the incident side end away from the excitation light source 24. Become. Therefore, even if the number of excitation light sources is reduced, the amount of excitation light E irradiated from the incident side end to the emission side end of the laser medium 23 can be increased corresponding to the cross-sectional area of the laser medium 23. Therefore, the number of parts of the laser generator 12 can be suppressed.

(4) Since only one laser medium 23 is provided, the laser generator 12 can be configured more easily.
In addition, you may change embodiment of this invention as follows.

  In the above embodiment, the excitation light source 24 is provided so as to irradiate the excitation light E obliquely from the emission side to the incident side of the laser medium 23. However, other than this, for example, as shown in FIG. 2, a plurality of excitation light sources 40 are provided on the side of the laser medium 23, and the amount of light corresponding to the cross-sectional area of the laser medium 23 from the direction orthogonal to the optical axis L of the seed light You may comprise so that the excitation light of each may be irradiated.

  In the above embodiment, the excitation light source 24 is provided corresponding to each corner of the emission side end of the laser medium 23. However, for example, on the top, bottom, left and right of the laser medium 23 when viewed from the optical axis L direction. You may arrange.

  In the above embodiment, four excitation light sources 24 are provided in the circumferential direction of the optical axis L on the emission side from the laser medium 23, but are not limited to this, and 1 to 3 or 5 or more are provided. Also good.

  In the above embodiment, the excitation light source 24 is provided so that the amount of excitation light E irradiated from the incident side end to the emission side end of the laser medium 23 increases corresponding to the cross-sectional area of the laser medium 23. However, other than this, for example, a uniform amount of light may be irradiated from the incident side end to the emission side end.

  The laser medium 23 of the above embodiment is configured by a plurality of laser medium pieces 50a, 50b, and 50c arranged in parallel in the optical axis L direction of the seed light as shown in FIG. 3 (three in FIG. 3). Also good. The laser medium pieces 50a to 50c are provided in close contact with each other. Further, the area of the emission surface of the laser medium piece 50a arranged closest to the seed light source 21 and the area of the incident surface of the subsequent laser medium piece 50b are formed to be substantially equal, and the emission surface of the laser medium piece 50b. And the area of the incident surface of the laser medium piece 50c in the subsequent stage are formed to be substantially equal. According to such a configuration, the laser medium can be formed large as a whole, and the seed light can be amplified to a higher beam power. Also, as shown in FIG. 4, a plurality of laser medium pieces 60a, 60b, 60c may be provided separately in the direction of the optical axis L. Further, the area of the incident surface of the subsequent laser medium piece 50b is formed larger than the area of the emission surface of the laser medium piece 60a arranged closest to the seed light source 21, and the laser medium piece 50b is emitted. The area of the incident surface of the subsequent laser medium piece 50c is formed larger than the area of the surface. Moreover, the excitation light source 61 of the structure similar to the said embodiment is provided with respect to each of the laser medium pieces 60a-60c. Even in such a configuration, the same operation and effect as the configuration shown in FIG. 3 as described above can be obtained. In the configuration shown in FIGS. 3 and 4, two or four or more laser medium pieces may be configured.

  In the above embodiment, the YAG crystal doped with ytterbium is used as the laser medium 23. However, the present invention is not limited to this. For example, a sapphire crystal doped with titanium (Ti) may be used. Those composed of other substances may also be used.

  In the above embodiment, the laser medium 23 has a rectangular cross section orthogonal to the optical axis L, but is not limited thereto, and may be, for example, a circular cross section. According to this configuration, the beam spot of the laser light emitted from the laser medium 23 can be made circular. Further, in this configuration, when a plurality of excitation light sources 24 are provided at equal intervals in the circumferential direction of the optical axis L, the laser light can be amplified with a good balance.

  In the above embodiment, the seed light source 21 that emits the seed light is provided, and the light emitting element emits laser light (stimulated emission) when the seed light is incident on the laser medium 23. Alternatively, the laser beam may be obtained by spontaneous emission of a light emitting element excited instead of seed light.

  In the above-described embodiment, the laser processing apparatus that performs the marking process has been described as an example. However, for example, the laser processing apparatus may be used in the same manner for a workpiece that performs cutting or welding on the workpiece.

It is a schematic block diagram which shows the laser processing apparatus in this embodiment. It is a schematic block diagram which shows the laser generator of another example. It is a schematic block diagram which shows the laser generator of another example. It is a schematic block diagram which shows the laser generator of another example.

Explanation of symbols

  E ... excitation light, L ... optical axis of seed light, W ... work as workpiece 10 laser processing device, 12 laser generating device, 21 seed light source, 22 optical amplifier, 23 laser medium, 24 40, 61 ... excitation light source, 50a-50c, 60a-60c ... laser medium piece.

Claims (7)

A laser medium made of a solid doped with a light emitting element and an excitation light source that excites the light emitting element by irradiating the laser medium with excitation light, and when the excited light emitting element returns from an excited state to a base state An optical amplifier that is amplified by the emitted laser light and emits the amplified laser light from the tip of the laser medium is configured,
The laser medium is formed so that a cross-sectional area perpendicular to the optical axis of the emitted laser light increases from the base end to the tip.
The excitation light source is configured so that the amount of the excitation light irradiated from the proximal end portion to the distal end portion of the laser medium is increased corresponding to a cross-sectional area of the laser medium. . The laser generator according to claim 1, wherein
The excitation light source irradiates the excitation light from the distal end side to the proximal end side of the laser medium, and the amount of the excitation light irradiated from the proximal end portion to the distal end portion of the laser medium is A laser generator characterized by being provided so as to increase in size corresponding to a cross-sectional area. The laser generator according to claim 1, wherein
A plurality of the excitation light sources are provided,
The plurality of excitation light sources respectively irradiate with excitation light having a light amount corresponding to a cross-sectional area of the laser medium from a direction orthogonal to an optical axis of laser light emitted from the laser medium. In the laser generator of any one of Claims 1-3,
The laser medium is composed of a plurality of laser medium pieces arranged in parallel in the optical axis direction of the emitted laser light, and the plurality of laser medium pieces has an area of an incident surface of the laser medium piece arranged in the subsequent stage, The laser generator is formed so as to be larger than the area of the emission surface of the laser medium piece arranged on the substrate. In the laser generator of any one of Claims 1-4,
The laser medium has a circular cross-sectional area perpendicular to the optical axis of the emitted laser light,
2. A laser generator according to claim 1, wherein a plurality of the excitation light sources are provided at equal intervals in the circumferential direction of the optical axis. In the laser generator of any one of Claims 1-5,
A laser generator, comprising: a seed light source for causing the light emitting element to emit seed light into the laser medium.   A laser processing apparatus that performs processing on an object to be processed using laser light emitted from the laser generator according to claim 1.

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