WO2018037538A1

WO2018037538A1 - Laser amplifying medium, laser oscillator, and laser amplifier

Info

Publication number: WO2018037538A1
Application number: PCT/JP2016/074844
Authority: WO
Inventors: 今井　信一; 晃宏棚橋; 加藤　一夫; 松本　太成
Original assignee: 株式会社メガオプト
Priority date: 2016-08-25
Filing date: 2016-08-25
Publication date: 2018-03-01

Abstract

A laser amplifying medium according to the present embodiment includes a solid-state laser medium and a pair of reflectors, and can be applied to a side-pumped laser oscillator or the like. The solid-state laser medium has a refractive index within the range of 1.7 through 1.9 with respect to excitation light or the like, and has a bottom face substantially formed into a parallelogram with one inner angle forming an acute angle within the range of 58 through 62 degrees. One of the surfaces forming the acute angle is disposed in an amplification optical path while excitation light is incident on the other surface. The pair of reflectors is disposed on a portion of the surface whereon the excitation light is incident and on a surface opposite thereto, thereby serving to deflect the excitation light that propagates through the solid-state laser medium in the traveling direction.

Description

Laser amplification medium, laser oscillator and laser amplifier

The present invention relates to a laser amplification medium, a laser oscillator, and a laser amplifier.

In a Fabry-Perot resonator in which a laser amplification medium is installed, the basic laser oscillator exceeds a certain intensity by resonating the light component of the natural wavelength emitted from the laser amplification medium excited in the inverted distribution state. Outputs coherent light (oscillation light). In a general solid-state laser, a solid-state laser medium is applied as a laser amplification medium, and as its excitation method, optical excitation that causes an inversion distribution state in the solid-state laser medium by laser light irradiation is mainly employed.

The following Patent Document 1 discloses a laser excitation type solid-state laser as one form of a light excitation type solid-state laser. For example, in many of Nd: YAG lasers to which a YAG crystal (solid laser medium) to which Nd (neodymium) is added as a laser amplification medium is applied, the solid laser medium is excited by output light of a laser diode. In addition, many of Ti: sapphire lasers to which sapphire (solid laser medium) to which Ti (titanium) is added as a laser amplifying medium are applied have twice the output light of an argon laser or Nd: YAG laser as excitation light. Harmonic light is applied.

In addition, as a form of photoexcitation by laser light irradiation, a side pump type shown in FIG. 1 (a) and an end pump type shown in FIG. 1 (b) are mainly known. Further, in this specification, the propagation path of the excitation light that enters the solid laser medium from the excitation light source is referred to as “excitation light path”. A propagation path (including a resonance optical path) of oscillation light that reciprocates on the resonance optical path in the resonator and is partially output to the outside of the resonator is referred to as an “oscillation optical path”. Further, the propagation path of the amplified light introduced into the solid laser medium and the propagation path of the amplified light amplified by the solid laser medium are collectively referred to as an “amplification optical path”.

Japanese Patent Laid-Open No. 2013-135075

The inventors have studied conventional laser oscillators, particularly laser-excited solid-state lasers, and have found the following problems. That is, the conventional laser oscillator to which the solid laser medium is applied as the laser amplification medium includes an end pump type laser oscillator 10A (FIG. 1A) and a side pump type laser oscillator 10B (FIG. 1B). It has been known.

For example, as shown in FIG. 1A, the end pump type laser oscillator 10A includes an excitation light source 20, a laser amplification medium 30, and a resonator in which the laser amplification medium 30 is housed. When the excitation light L1 having the first wavelength is irradiated from the excitation light source 20 toward the laser amplification medium 30, an inversion distribution state is formed in the laser amplification medium 30 by light excitation by the excitation light L1, and the first wavelength is Light of a different second wavelength is emitted. A part of the light having the second wavelength thus emitted is output to the outside of the resonator as coherent oscillation light L2. The resonator is composed of a pair of resonator mirrors, and the first resonator mirror 40A disposed on the one input / output surface 30a side of the laser amplification medium 30 transmits the excitation light L1, while the excitation light This is a high reflection mirror having a high reflectance with respect to the light output from the laser amplification medium 30 optically excited by L1. The second resonator mirror 40B disposed on the other input / output surface 30b side of the laser amplifying medium 30 transmits a part of the light generated in the laser amplifying medium 30 as the oscillation light L2, while the rest is a laser. This is an output coupling mirror that reflects to the amplification medium 30 side.

As shown in FIG. 1A, the end-pump type laser oscillator 10A having the above-described structure includes an excitation light path (propagation path of the excitation light L1) and an oscillation light path (oscillation light L2 including a resonance light path). Propagation paths) match. Therefore, for example, high-efficiency oscillation can be achieved by improving the consistency between the distribution of the active substance (hereinafter referred to as “active distribution”) and the volume in the resonator in the laser amplifying medium 30 composed of a solid laser medium or the like. It becomes possible. On the other hand, in such an end-pump type optical excitation, a refractive index distribution is generated in the laser amplification medium 30 due to a heat distribution centered on the excitation optical path. Therefore, a slight deviation between the excitation optical path and the oscillation optical path causes a large optical loss and prevents good laser oscillation.

Similarly to the end-pump type laser oscillator 10A, the side-pump type laser oscillator 10B shown in FIG. 1B also has an excitation light source 20 that outputs the excitation light L1 having the first wavelength and optical excitation by the excitation light L1. The intensity of the excitation light L1 that is disposed between the laser amplification medium 30 that emits light of the second wavelength, and between the excitation light source 20 and the laser amplification medium 30 and is irradiated on the entire excitation light incident surface of the laser amplification medium 30 is determined. The optical system 50 for making uniform and the resonator which accommodated this laser amplification medium 30 are provided. The excitation light incident surface is a surface different from the input /

output surfaces

30a and 30b arranged on the oscillation optical path. Of the pair of resonator mirrors constituting the resonator, the first resonator mirror 40A disposed on the one input / output surface 30a side of the laser amplification medium 30 is higher than the light output from the laser amplification medium 30. This is a highly reflective mirror having reflectivity. The second resonator mirror 40B disposed on the other input / output surface 30b side of the laser amplifying medium 30 transmits a part of the light generated in the laser amplifying medium 30 as the oscillation light L2, while the rest is a laser. This is an output coupling mirror that reflects to the amplification medium 30 side.

In the side-pump type laser oscillator 10B having the above-described structure, the excitation light L1 is irradiated over the entire laser amplification medium 30 in order to intersect the excitation light path and the oscillation light path at an angle or at an angle close to the orthogonal. However, in the laser amplification medium 30 orthogonal to the oscillation optical path, the power density of pumping light (W / cm ² ) gradually decreases as the power of the pumping light is absorbed by the active substance. As a result, the active state of the substance in the laser amplifying medium 30 varies (the activity distribution is shaded). Such uneven distribution of the active substance in the laser amplification medium 30 may hinder the generation of a good beam shape of the oscillation light L2. In addition, the oscillation optical path and the excitation optical path are configured separately (configured so as to be orthogonal to each other or intersect at an angle close to each other), so that the installation configuration should not be larger than the end pump type laser oscillator. I couldn't.

Further, the laser amplification medium 30 can be applied to a laser amplifier. FIG. 1C shows a schematic configuration of a side pump type laser amplifier 20 to which a solid laser medium is applied as the laser amplification medium 30. ing. The laser amplifier 20 includes a laser amplification medium 30, an excitation light source 20 that outputs excitation light L 1 having a first wavelength for optically exciting the laser amplification medium 30, and the laser amplification medium 30 and the excitation light source 20. And an optical system 50 for making the intensity of the excitation light L1 irradiated to the entire laser amplification medium 30 uniform. The laser amplification medium 30 has an input unit 31 for taking in light of the second wavelength (amplified light L3) output from the optical signal source 60, and is opposed to the input unit 31, and is amplified light from the laser amplification medium 30. An output unit 32 for outputting L4 is provided.

In FIGS. 1A and 1B in which the schematic configurations of the

laser oscillators

10A and 10B are shown, optics that enable beam shaping and condensing of the excitation light L1 irradiated to the laser amplification medium 30. Details of the elements are omitted. Further, in FIG. 1C showing a schematic configuration of the laser amplifier 20, details of optical elements that enable beam shaping and focusing of the excitation light L1 and the amplified light L3 irradiated to the laser amplification medium 30 are shown. Is omitted.

The present invention has been made to solve the above-described problems, and enables miniaturization and high-efficiency and stable laser output as compared with conventional laser oscillators and laser amplifiers. It is an object of the present invention to provide a laser amplifying medium having a structure for achieving the above, and a laser oscillator and a laser amplifier to which the laser amplifying medium is applied.

In the laser amplifying medium according to the present invention, an inversion distribution state is formed inside by light excitation with excitation light of the first wavelength, and light having a second wavelength different from the first wavelength is generated. The laser amplification medium includes a solid laser medium, a first reflector, and a second reflector. The solid-state laser medium has a refractive index that falls within a range of 1.8 ± 0.1 for light of at least the first and second wavelengths. In addition, the solid laser medium is a prism that is defined by a bottom surface that is a substantially parallelogram defined by an acute angle in which one of the inner angles is within a range of 60 ± 2 degrees, and a side surface that is defined by a side surface that intersects the side of the bottom surface. Has a shape. Side surfaces of the solid-state laser medium are a first side surface that functions as an input / output surface for light of the second wavelength, a second side surface that faces the first side surface, and functions as an input / output surface for light of the second wavelength, and the first side surface. It is comprised by the 4th side surface which adjoins so that an acute angle may be made, and in which excitation light injects, and the 3rd side surface facing a 3rd side surface. The first reflector is provided on the remaining region of the third side surface excluding the excitation light incident region where the excitation light reaches with the reflection surface facing the third side surface. The second reflector is provided on the fourth side surface with the reflecting surface facing the fourth side surface.

In the laser amplification medium according to the present invention, on the excitation light incident side of the solid-state laser medium, the angle formed between the excitation light incident surface and the input / output surface located on the oscillation optical path (or amplification optical path) is substantially equal to the solid-state laser. The Brewster angle of the medium is set. In addition, in a side-pump type laser oscillator or laser amplifier to which the laser amplification medium is applied, in order to enable low-loss light incidence on both the excitation light incident surface and the input / output surface, the incident angles with respect to these surfaces are It is set to the Brewster angle of the solid laser medium. Therefore, when the laser amplification medium is a laser oscillator or laser amplifier, the excitation light path and the oscillation light path (or amplification light path) can be made parallel on the excitation light incident side of the solid-state laser medium, resulting in simple excitation optics. System configuration is possible. This makes it possible to avoid an increase in the size of the device structure (similar to the case of end-pump type optical pumping) and to separate the oscillation optical path (resonant optical path portion) and the excitation optical path in the solid laser medium. That is, according to the present invention, the optical path deviation caused by the heat distribution due to the excitation distribution is eliminated, and it is possible to realize extremely stable laser oscillation. Furthermore, according to the present invention, by providing a pair of reflectors on opposite sides of the solid-state laser medium, the optical path length of the excitation light propagating in the solid-state laser medium can be compared with the case of the end pump type optical excitation. Thus, the pumping efficiency of the solid-state laser medium can be greatly improved while using side pump type optical pumping.

FIG. 3 is a diagram showing an example of a schematic configuration of each of an end pump type laser oscillator, a side pump type laser oscillator, and a side pump type laser amplifier. These are assembly process drawings for demonstrating the structure of the laser amplification medium which concerns on this embodiment. These are the figures for demonstrating the function and effect of the laser amplification medium which concern on this embodiment. These are the figures for demonstrating the improvement of the excitation efficiency in this embodiment. These are figures which show an example of schematic structure of the laser oscillator concerning this embodiment. These are figures which show an example of the schematic structure of the laser amplifier which concerns on this embodiment.

[Description of Embodiment of Present Invention]
First, the contents of the embodiments of the present invention will be listed and described individually.

(1) As one aspect of the present embodiment, the laser amplification medium generates an inversion distribution state inside by optical excitation by excitation light of the first wavelength, and generates light having a second wavelength different from the first wavelength. . The laser amplification medium includes a solid laser medium, a first reflector, and a second reflector. The solid-state laser medium has a refractive index that falls within 1.8 ± 0.1 (in the range of 1.7 to 1.9 centered on 1.8) for at least the first and second wavelengths of light. The solid-state laser medium has a bottom surface that is a substantially parallelogram defined by an acute angle in which one of the inner angles falls within a range of 60 ± 2 degrees (a range of 58 to 62 degrees centered on 60 degrees); Each has a prismatic shape defined by side surfaces intersecting the sides of the bottom surface. Side surfaces of the solid-state laser medium are a first side surface that functions as an input / output surface for light of the second wavelength, a second side surface that faces the first side surface, and functions as an input / output surface for light of the second wavelength, and the first side surface. It is comprised by the 4th side surface which adjoins so that an acute angle may be made, and in which excitation light injects, and the 3rd side surface facing a 3rd side surface. The first reflector is provided on the remaining region of the third side surface excluding the excitation light incident region (including the excitation light incident position) where the excitation light reaches with the reflecting surface facing the third side surface. It has been. The second reflector is provided on the fourth side surface with the reflecting surface facing the fourth side surface.

As described above, in an end-pump type laser oscillator, the laser amplification medium is a special type applicable to a side-pump type laser oscillator and a laser amplifier in order to suppress the occurrence of optical loss due to the deviation between the excitation optical path and the oscillation optical path. It has a structure. On the other hand, as described above, in the side pump type laser oscillator and laser amplifier, in order to suppress the variation in the active state of the substance in the laser amplification medium, the excitation light is incident on the third side surface of the solid laser medium on which the excitation light is incident. A pair of reflectors having reflective surfaces facing each other are provided on the region excluding the region and on the fourth side surface facing the third side surface. The excitation light introduced into the solid-state laser medium with the incident angle set to the Brewster angle of the solid-state laser medium is reflected toward the solid-state laser medium by the reflecting surfaces of the pair of reflectors. Therefore, it becomes possible to lengthen the excitation light path in the solid-state laser medium as compared with the case of the end pump type laser oscillator (improvement of excitation efficiency).

(2) A side-pump type laser oscillator to which the laser amplification medium having the above-described structure is applied, specifically, as one aspect of the present embodiment, the laser amplification medium having the above-described structure, A resonator containing a laser amplification medium and an excitation light source are provided. The resonator is composed of a pair of resonator mirrors, and one (first resonator mirror) of the pair of resonator mirrors is output from the incident side of the laser amplification medium (the first side surface of the solid laser medium). It is a high reflection mirror arranged at a position where light of the second wavelength reaches. The other resonator mirror (second resonator mirror) is disposed at a position where the light of the second wavelength output from the second side surface of the solid-state laser medium reaches, and a part of the reached light is outside the resonator. This is an output coupling mirror that outputs to. The excitation light source outputs excitation light that should be incident on the excitation light incident area of the third side surface of the solid-state laser medium at a predetermined incident angle.

(3) On the other hand, as an aspect of this embodiment, a side-pump type laser amplifier introduces a laser amplification medium having the above-described structure, an excitation light source, and light to be amplified into the laser amplification medium. And an output unit for outputting amplified light. The excitation light source outputs excitation light that should be incident on the excitation light incident area of the third side surface of the solid-state laser medium included in the laser amplification medium at a predetermined incident angle. The input unit coincides with the first side surface of the solid-state laser medium, and the output unit coincides with the second side surface of the solid-state laser medium.

In both the laser oscillator and the laser amplifier, the first reflector on the third side and the fourth side on the third side in a state where the first side and the second side of the solid laser medium are arranged on the oscillation optical path or the amplification optical path. The second reflector has a posture in which each reflecting surface sandwiches the oscillation optical path or the amplification optical path. The excitation light introduced into the solid laser medium from the excitation light incident area on the third side is reciprocated in the solid laser medium a plurality of times by the pair of reflectors. Therefore, the uneven distribution state of the active substance in the solid-state laser medium is greatly improved over a wide range as compared with the side pump type conventional laser oscillator and laser amplifier.

(4) As an aspect of this embodiment, the solid-state laser medium may include sapphire to which Ti is added.

(5) As one aspect of the present embodiment, the excitation light preferably includes laser light having a wavelength falling within a range of 440 to 540 nm. The incident angle of the excitation light with respect to the third side surface of the solid-state laser medium is preferably set in the range of 58 to 62 degrees centered on 60 degrees.

As described above, the solid-state laser medium included in the laser medium applicable to the side-pump type laser oscillator and the laser amplifier includes the first wavelength excitation light, the second wavelength oscillation light, the third wavelength amplified light, and the amplifier. The bottom surface has a refractive index of 1.8 ± 0.1, and one of the inner angles (the angle formed by the first side surface and the third side surface) is a Brewster of the solid-state laser medium. It is a substantially parallelogram set to 60 ± 2 degrees corresponding to a corner. In addition, the excitation light is not irradiated on the entire third side surface of the solid-state laser medium, but the incident angle is set to the Brewster angle of the solid-state laser medium with respect to the excitation light incident area on the third side surface. Thus, the p-polarized component of the excitation light is efficiently (low loss) introduced into the solid-state laser medium. At this time, the excitation light path and the oscillation light path (or amplification light path) can be made parallel on the excitation light incident side of the solid-state laser medium, and as a result, a simple configuration of the excitation optical system becomes possible. In this case, the oscillation optical path (resonance optical path portion) and the excitation optical path in the solid-state laser medium can be separated while avoiding an increase in the size of the device structure (similar to the case of end pump type optical excitation). That is, in the solid-state laser medium, the optical path deviation caused by the heat distribution due to the excitation distribution is eliminated, and it is possible to realize extremely stable laser oscillation.

As described above, each aspect listed in this [Description of Embodiments of the Invention] is applicable to each of all the remaining aspects or to all combinations of these remaining aspects. .

[Details of the embodiment of the present invention]
Hereinafter, specific structures of the laser amplification medium, the laser oscillator, and the laser amplifier according to the present embodiment will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and it is intended that all the changes within the meaning and range equivalent to a claim are included. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(Laser amplification medium)
2A and 2B are assembly process diagrams for explaining the structure of the laser amplification medium 300 according to the present embodiment. 2A is an assembly process diagram when the laser amplification medium 300 is viewed from the upper surface side, and FIG. 2B is an assembly process diagram when the laser amplification medium 300 is viewed from the bottom surface side. is there.

As shown in FIGS. 2A and 2B, the laser amplification medium 300 according to the present embodiment includes a solid-state laser medium 310 and a pair of reflectors (a first reflector 320A and a second reflector). 320B is provided.

The solid laser medium 310 has an inversion distribution state formed therein by light excitation with excitation light having the first wavelength, and emits light having a second wavelength different from the first wavelength. The solid-state laser medium 310 has a refractive index that falls within a range of 1.7 to 1.9, centered at 1.8, for at least the light of the first and second wavelengths. As shown in FIGS. 2A and 2B, the solid-state laser medium 310 has a bottom surface 310e and a top surface 310f arranged to face each other, and each of the bottom surface 310e and the top surface 310f has an inner angle. One is a substantially parallelogram defined by an acute angle within a range of 58 to 62 degrees centered on 60 degrees. Further, the bottom surface 310e and the top surface 310f communicate with each other through four side surfaces, whereby the solid-state laser medium 310 has a prism shape defined by the bottom surface 310e and the four side surfaces intersecting the sides of the bottom surface 310e. Has a shape. The four side surfaces are a first side surface 310a that functions as an input / output surface for light of the second wavelength (light propagating on the oscillation optical path or the amplification optical path), and light of the second wavelength that faces the first side surface 310a. A second side surface 310b functioning as an input / output surface of the first side surface, a third side surface 310c adjacent to the first side surface 310a so as to form the acute angle and receiving excitation light, and a third side surface 310c facing the third side surface 310c. It is composed of four side surfaces 310d. That is, when each of the first side surface 310a and the second side surface 310b of the solid-state laser medium 310 is disposed on the oscillation optical path or the amplification optical path, it is adjacent to the first side surface 310a so as to make the acute angle (58 to 62 degrees). The third side surface 310c that serves as the incident surface of the excitation light.

Further, as shown in FIGS. 2A and 2B, a pair of reflectors is provided on the third side surface 310c and the fourth side surface 310d of the solid-state laser medium 310. Of the pair of reflectors, the first reflector 320A has a reflection surface 321A that reflects the excitation light propagating in the solid-state laser medium 310, and the excitation light is in a state where the reflection surface 321A faces the third side surface 310c. Is provided on the remaining region of the third side surface 310c excluding the excitation light incident region R that reaches. Of the pair of reflectors, the second reflector 320B is provided on the fourth side surface 310d with the reflecting surface 321B facing the fourth side surface 310d.

Each of the first reflector 320A and the second reflector 320B may be a high reflection mirror that reflects the excitation light, and directly on the third side surface 310c and the fourth side surface 310d of the solid-state laser medium 310. It may be a reflective coating provided. In the configuration in which high-reflection mirrors are installed as the first reflector 320A and the second reflector 320B, a structure is employed in which the reflecting

surfaces

321A and 321B do not directly touch the third side surface 310c and the fourth side surface 310d. May be. In this case, since the excitation light once emitted from the solid-state laser medium 310 is emitted almost at the Brewster angle, the reflection loss is kept to a minimum. On the other hand, when the excitation light reflected by the reflecting

surface

321A or 321B returns again into the solid-state laser medium 310, the incident angle becomes an angle close to the Brewster angle with low loss.

Next, the function and effect of the laser amplification medium 300 having the above-described structure will be described below with reference to FIG. 3, FIG. 4 (a), and FIG. 4 (b). FIG. 3 is a diagram for explaining the functions and effects of the laser amplification medium 300. 4 (a) and 4 (b) show the fluctuation of the excitation light density in the laser amplification medium 300 by the optical excitation according to the present embodiment, as shown in FIGS. 1 (b) and 1 (c). It is a figure for demonstrating comparing with the fluctuation | variation of the excitation light density in the laser amplification medium 30 by such optical excitation.

As shown in FIG. 3, the bottom surface 310e of the solid-state laser medium 310 has a first side surface 310a positioned on the oscillation light path (or amplification light path) P1 on the excitation light incident side (left side in FIG. 3), and the excitation light path. The angle formed with the third side surface 310c disposed on P2 is set to the Brewster angle θ _B of the solid-state laser medium 310. Further, in order to reduce reflection loss at the time of incidence of light (oscillation light or amplified light) propagating through the oscillation optical path P1 and excitation light propagating through the excitation optical path P2, the incident angles with respect to the first side surface 310a and the third side surface 310c, respectively. It is both Brew - set to static angle theta _B. Specifically, the solid-state laser medium 310 applicable to the present embodiment has a refractive index of 1.8 ± 0.1 with respect to the wavelength of the excitation light and the amplification wavelength, and parallel sides defining the bottom surface 310e and the top surface 310f. One of the interior corners of the shape is 60 ± 2 degrees. At this time, as shown in FIG. 3, substantially Brew - the first side surface 310a and the third side surface 310c to sandwich the internal angle that is set in the static angle theta _B, oscillation optical path (or amplification path) P1 and the excitation light path P2 is set. The light propagating through the oscillation optical path (or amplification optical path) P1 and the pumping light propagating through the pumping optical path P2 are respectively incident on the first side surface 310a and the third side surface 310c within the range of the Brewster angle θ _B ± 2 degrees, respectively. P-polarized components are introduced into the solid-state laser medium 310. In particular, the excitation light (p-polarized component) introduced into the solid-state laser medium 310 is reflected by the first reflector 320A and the second reflector 320B. Therefore, the excitation light path in the solid-state laser medium 310 is much longer than in the case of the conventional end-pump type or side-pump type optical excitation, and the active state of the substance in the solid-state laser medium 310 is kept uniform. It becomes possible.

The improvement of the excited state as described above can be easily understood from FIG. That is, in FIG. 4B, a graph 400A shows a change in excitation light density when the laser amplification medium 300 according to the present embodiment is photoexcited by a side pump type as shown in FIG. As a comparative example, as shown in FIG. 1B, a change in excitation light density when optically excited by a side pump type that irradiates the entire one side surface of the laser amplification medium 30 with excitation light is shown. The horizontal axis in FIG. 4B indicates the distance (in arbitrary units) from the center of each of the

laser amplification media

30 and 300, as shown in FIG. 4A.

(Laser oscillator)
FIG. 5 is a diagram showing an example of a schematic structure of the side pump type laser oscillator 100 according to the present embodiment. A side-pump type laser oscillator 100 shown in FIG. 5 includes an excitation light source 20, a laser amplification medium 300 having the structure shown in FIG. 3, a resonator containing the laser amplification medium 30, and an excitation light source 20 And the laser amplifying medium 300 are provided with an incident angle adjusting mechanism 400. The laser amplifying medium 300 has an inverted distribution state formed by optical excitation by the first wavelength excitation light L1 output from the excitation light source 20, and emits light having a second wavelength different from the first wavelength. A part of the light having the second wavelength thus emitted is output to the outside of the resonator as coherent oscillation light L2. Further, in the excitation light incident side of the solid-state laser medium 310 interposed between the first side surface 310a and the third side 310c, one (sharp portion) of the inner angle is set to Brewster angle theta _B. The resonator includes a first resonator mirror (high reflection mirror) 40 </ b> A arranged on the first side surface (light input / output surface of second wavelength light) 310 a of the solid laser medium 310, and a second side surface of the solid laser medium 310. (Second-wavelength light input / output surface) A second resonator mirror (output coupling mirror) 40B arranged on the 310b side is formed. The incident angle adjusting mechanism 400 provided between the excitation light source 20 and the laser amplification medium 300 is a beam of excitation light L1 that is incident on the excitation light incident region R (included in the third side surface 310c) of the laser amplification medium 300. In addition to shaping, in order to adjust the incident angle of the excitation light L1, it is configured by optical elements such as a lens system and a reflector that can deflect and collect the light.

As a specific example of the side-pump type laser oscillator 100 according to the present embodiment, a solid-state laser medium 310 that constitutes a part of the laser amplification medium 300 according to the present embodiment has a 1.76 wavelength for light having a wavelength of 800 nm. It consists of Ti: sapphire (sapphire to which titanium is added) having a refractive index. The excitation light L1 is laser light having a wavelength of 532 nm, and second harmonic light of Nd: YAG laser is applicable. Note that the refractive index of Ti: sapphire is 1.77 for light having a wavelength of 532 nm. The inner angle of the laser amplification medium 300, that is, the angle formed by the first side surface 310a and the third side surface 310c is set to 60.4 degrees corresponding to the Brewster angle with respect to light having a wavelength of 800 nm.

Incident angle of the excitation light L1 (light propagating through the excitation optical path) with respect to the third side surface 310c and light (between the first resonator mirror 40A and the second resonator mirror 40B) that propagates through the oscillation optical path with respect to the first side surface 310a. The incident angles of the light propagating through the resonance optical path are set to 60 degrees, and the respective p-polarized components are efficiently introduced into the solid-state laser medium 310. In addition, the reflectance in each of the 1st side surface 310a and the 3rd side surface 310c at this time is 1% or less. Further, the excitation optical path (corresponding to the optical path P2 in FIG. 3) and the oscillation optical path (corresponding to the optical path P1 in FIG. 3) are substantially parallel.

The cross section of the oscillation optical path is 6 mm × 6 mm, the long side of the parallelogram defining the bottom surface 310e and the top surface 310f of the solid laser medium 310 is 12 mm, and the concentration of Ti added to the solid laser medium 310 is for light with a wavelength of 532 nm To 1.15 cm ⁻¹ . The first resonator mirror 40A is disposed perpendicular to the oscillation optical path of the solid-state laser medium 310. The first resonator mirror 40A is a highly reflective mirror having a dichroic characteristic with a reflectance of 99% or more for light having a wavelength of 800 nm and a transmittance of 99% or more for light having a wavelength of 532 nm. The second resonator mirror 40B is a partial reflection mirror (output coupling mirror) having a reflectance of 60% or more for light having a wavelength of 800 nm and a transmittance of 40% or less for light having a wavelength of 800 nm.

In the laser oscillator 100 configured as described above, when the excitation light L1 having a wavelength of 532 nm and an output of 30 mJ was incident on the laser amplification medium 300, oscillation with a wavelength of 800 nm and an output energy of 7.5 mJ was confirmed. Further, the output (power of the oscillation light L2) was extremely stable with no temporal and spatial fluctuations observed.

(Laser amplifier)
FIG. 6 is a diagram showing an example of a schematic structure of the side pump type laser amplifier 200 according to the present embodiment. A side pump type laser amplifier 200 shown in FIG. 6 outputs a laser amplification medium 300 having the structure shown in FIG. 3 and pumping light L1 having a first wavelength for optically exciting the laser amplification medium 300. An excitation light source 20, and an incident angle adjusting mechanism 400 that is disposed between the laser amplification medium 300 and the excitation light source 20 and adjusts the incident angle of the excitation light L1 with respect to the third side surface 310c of the laser amplification medium 300 are provided. . The first side surface 310 a of the solid-state laser medium 310 functions as an input unit for taking in light of the second wavelength (amplified light L 3) output from the optical signal source 60, and the second side surface 310 b is the solid-state laser medium 310. It functions as an output unit for outputting the amplified light L4 from the inside. It is apparent from the above description of the laser oscillator 100 that the laser amplifier 200 can be configured on the essence of a laser oscillator configured by an amplifier and optical feedback.

In the laser amplifier 200, the angle formed by the first side surface 310a and the third side surface 310c of the solid-state laser medium 310 is set to the Brewster angle θ _B of the solid-state laser medium 310. The incident angle of the excitation light L1 from the excitation light source 20 with respect to the excitation light incident region R on the third side surface 310c and the incident angle of the amplified light L3 from the optical signal source 60 with respect to the first side surface 310a are since the both are set to Brewster angle theta _B, excitation light path excitation light L1 from the excitation light source 20 propagates (corresponding to an optical path P2 in FIG. 3), the amplified light L3 from the optical signal source 60 The propagating amplification optical path (corresponding to the optical path P1 in FIG. 3) is substantially parallel. Therefore, on the excitation light incident side (left side in FIG. 6) of the laser amplification medium 300, the incident angle adjusting mechanism 400 is disposed on the excitation light path and the amplification light path. The incident angle adjusting mechanism 400 includes the excitation light L1 incident on the excitation light incident region R (included in the third side surface 310c) of the laser amplification medium 300 and the beam of the amplified light L3 incident on the first side surface 310a. In addition to shaping, in order to adjust the incident angles of the light L1 and the light L3, they are constituted by optical elements such as a lens system and a reflector that enable respective deflection and condensing.

In the above-described embodiment, an example in which a Ti: sapphire crystal is applied as the solid laser medium 310 included in the laser amplification medium 300 is shown, but the applicable solid laser medium 310 is not limited to this. Needless to say, another solid-state laser medium having an equivalent refractive index may be used.

In the above-described embodiment, laser light having a wavelength of 532 nm is applied as excitation light. However, it is obvious from laser physics that laser light having a wavelength of 440 nm to 540 nm is effective as excitation light for a Ti: sapphire laser. is there.

The present invention can be applied to laser processing technology applied in various industrial fields such as medical care and machinery.

DESCRIPTION OF SYMBOLS 20 ... Excitation light source, 40A ... 1st resonator mirror (high reflection mirror), 40B ... 2nd resonator mirror (output coupling mirror), 60 ... Optical signal source, 100 ... Laser oscillator, 200 ... Laser amplifier, 300 ... Laser Amplifying medium, 310 ... solid laser medium, 310a ... first side, 310b ... second side, 310c ... third side, 310d ... fourth side, 310e ... bottom, 310f ... top, 320A ... first reflector, 320B ... Second reflector, 321A, 321B ... reflecting surface, 400 ... incident angle adjusting mechanism, R ... excitation light incident region.

Claims

A laser amplification medium in which an inversion distribution state is formed inside by light excitation by excitation light of a first wavelength, and emits light of a second wavelength different from the first wavelength;
At least the first and second wavelengths of light have a refractive index that falls within a range of 1.7 to 1.9 centered on 1.8, and one of the inner angles is 58 to 62 centered on 60 degrees. A substantially parallelogram-shaped bottom surface defined by an acute angle within a range of degrees and a side surface defined by a side surface that intersects the side of the bottom surface, and the side surface is light of the second wavelength. A first side surface functioning as an input / output surface, a second side surface facing the first side surface and functioning as an input / output surface for light of the second wavelength, and adjacent to the first side surface so as to form the acute angle. And a solid-state laser medium composed of a third side surface on which the excitation light is incident and a fourth side surface facing the third side surface,
On the remaining area of the third side surface excluding the excitation light incident area where the excitation light reaches in a state where the reflection surface reflecting the excitation light propagating in the solid laser medium faces the third side surface A first reflector provided;
A second reflector provided on the fourth side surface with a reflecting surface reflecting the excitation light propagating in the solid laser medium facing the fourth side surface;
A laser amplification medium characterized by comprising:
A laser amplification medium according to claim 1;
A first resonator mirror disposed at a position where the light of the second wavelength output from the first side surface of the solid-state laser medium included in the laser amplification medium reaches; and the second side surface of the solid-state laser medium. A resonator constituted by a second resonator mirror disposed at a position where the light of the second wavelength output from
An excitation light source that outputs the excitation light to be incident at a predetermined incident angle on the excitation light incident region of the third side surface of the solid-state laser medium;
A laser oscillator comprising:
3. The laser oscillator according to claim 2, wherein the solid-state laser medium includes sapphire to which Ti is added.
The excitation light includes laser light having a wavelength falling within a range of 440 to 540 nm,
The laser oscillator according to claim 3, wherein an incident angle of the excitation light with respect to the third side surface of the solid-state laser medium is set in a range of 58 to 62 degrees centered on 60 degrees.
A laser amplification medium according to claim 1;
An excitation light source that outputs the excitation light to be incident at a predetermined incident angle on the excitation light incident region of the third side surface of the solid-state laser medium included in the laser amplification medium;
An input unit coinciding with the first side surface of the solid-state laser medium and for introducing amplified light into the solid-state laser medium;
An output unit that matches the second side surface of the solid-state laser medium and outputs amplified light amplified in the solid-state laser medium;
A laser amplifier comprising:
6. The laser amplifier according to claim 5, wherein the solid-state laser medium includes sapphire to which Ti is added.
The excitation light includes laser light having a wavelength falling within a range of 440 to 540 nm,
The laser amplifier according to claim 6, wherein an incident angle of the excitation light with respect to the third side surface of the solid-state laser medium is set in a range of 58 to 62 degrees centered on 60 degrees.