阅读说明：本技术 光吸收层和具有光吸收层的接合体 (Light-absorbing layer and bonded body having light-absorbing layer ) 是由 山崎芳树 三上充 于 2019-10-28 设计创作，主要内容包括：一种光吸收层,所述光吸收层通过与激光介质接合而构成接合体,其特征在于,所述光吸收层包含玻璃材料,并且在激光介质的振荡波长(波长大于等于650nm且小于1400nm)下,所述光吸收层具有0.1cm～(-1)～10.0cm～(-1)的吸收系数,所述光吸收层与激光介质的折射率差在±0.1以内,并且所述光吸收层与激光介质的线性热膨胀系数差在±1ppm/K以内。本发明的课题在于提供一种用于防止寄生振荡的光吸收层、以及能够抑制制造成本并且容易进行用于制作接合体的加工的材料。(A light-absorbing layer which is joined to a laser medium to form a joined body, wherein the light-absorbing layer contains a glass material and has a wavelength of 0.1cm at an oscillation wavelength of the laser medium (a wavelength of 650nm or more and 1400nm or less) ‑1 ～10.0cm ‑1 The difference between the refractive indexes of the light-absorbing layer and the laser medium is within + -0.1, and the difference between the linear thermal expansion coefficients of the light-absorbing layer and the laser medium is within + -1 ppm/K. The invention provides a light absorption for preventing parasitic oscillationA material which can suppress the production cost and can be easily processed for producing a joined body.)

1. A light-absorbing layer which is joined to a laser medium to form a joined body, wherein the light-absorbing layer contains a glass material and is vibrated in the laser mediumAt oscillation wavelength (wavelength of 650nm or more and less than 1400nm), the light absorption layer has a thickness of 0.1cm^-1～10.0cm^-1The difference between the refractive indexes of the light-absorbing layer and the laser medium is within + -0.1, and the difference between the linear thermal expansion coefficients of the light-absorbing layer and the laser medium is within + -1 ppm/K.

2. The light-absorbing layer according to claim 1, wherein the light-absorbing layer contains at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Sb, Te, La, Sm, Gd, Dy, Tb, Lu and Bi.

3. The light-absorbing layer according to claim 1 or 2, wherein the light-absorbing layer has a melting point of less than 1500 ℃.

4. The light-absorbing layer according to any one of claims 1 to 3, wherein the laser medium contains Nd: YAG and Yb: YAG, Nd: YVO₄Any one of Ti-sapphire and Cr-forsterite.

5. A bonded body obtained by bonding and integrating the light-absorbing layer according to any one of claims 1 to 4 with a laser medium.

Technical Field

The present invention relates to a light-absorbing layer joined to a laser medium to form a joined body and a joined body having the light-absorbing layer, and more particularly, to a light-absorbing layer and a joined body having a light-absorbing layer suitable for preventing parasitic oscillation of a laser oscillator/amplifier.

Background

Standard laser light is used to excite a laser medium that is a phosphor and optically amplify it in a resonator sandwiched by optically opposed high reflectivity mirrors. In addition, laser media have applications as amplifiers for amplifying laser beam outputs generated from other media, in addition to the case where the laser media themselves serve as oscillation sources.

Incidentally, in designing a laser application, attention needs to be paid to parasitic oscillation. Parasitic oscillations refer to: the end face of the laser medium serves as a reflecting surface, and laser oscillation occurs in a direction different from the direction of the surface formed by the opposing mirrors.

When the parasitic oscillation occurs, the output is reduced as compared with the laser beam predicted from the original resonator constituted by the opposing mirrors. Therefore, in order to prevent such parasitic oscillation, a light absorption layer for preventing parasitic oscillation, which has a refractive index of the same degree as that of the core, is formed around the laser medium (hereinafter, may be referred to as a core).

YAG materials have been known as a representative phosphor (laser medium) of high-power lasers. As a high power laser (amplifier) application, development in Nd: a YAG polycrystalline material, and Sm-doped light-absorbing layer YAG polycrystalline material around the YAG polycrystalline material (non-patent documents 1 and 2). Further, by mixing a YAG polycrystalline body doped with Cr with Yb: YAG laser polycrystals are joined, and high-power operation is also confirmed (non-patent document 3).

Documents of the prior art

Non-patent document

Non-patent document 1: A.Ikesue, Y.L.Aung, Nature Photonics 22,721-

Non-patent document 2: yamamoto, R.M. et al, Roc, adv.solid State Photon, Nara, Japan WC5(2008)

Non-patent document 3: s. Banerjee et al, Opt. Lett.37,2175-2177(2012)

Disclosure of Invention

Problems to be solved by the invention

However, the melting point of a single crystal of YAG doped with a transition metal is as high as 1970 ℃, and the production cost for growing a crystal from a liquid phase is high. In addition, since YAG has a high hardness (Knoop hardness: about 1500 kgf/mm)²) Therefore, a large amount of energy is required to be input in the polishing process. Further, since YAG needs to be heated to a high temperature even in the case of thermal bonding, there is a disadvantage in producing a bonded body of the laser medium (core) and the light absorbing layer.

In addition, in recent years, it has been reported that laser host materials other than YAG are developed for high power applications, and light absorbing layers for preventing parasitic oscillation are also required for these materials, but since these materials have high melting points and high hardness, problems with manufacturing costs and processing are expected to occur similarly to the case of YAG materials.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a light absorbing layer and a bonded body for preventing parasitic oscillation, and a material which can suppress manufacturing cost and facilitate processing for manufacturing the bonded body.

Means for solving the problems

Embodiments of the present invention that can solve the above problems have the following gist: a light-absorbing layer bonded to a laser medium to form a bonded body, wherein the light-absorbing layer contains a glass material and has a wavelength of 0.1cm at an oscillation wavelength (wavelength of 650nm or more and less than 1400nm) of the laser medium^-1～10.0cm^-1The difference between the refractive indexes of the light-absorbing layer and the laser medium is within + -0.1, and the difference between the linear thermal expansion coefficients of the light-absorbing layer and the laser medium is within + -1 ppm/K.

Effects of the invention

According to the present invention, there is provided an excellent effect that a light absorbing layer for preventing parasitic oscillation is provided, and processing for producing a bonded body can be easily performed while suppressing the production cost.

Drawings

Figure 1 shows a schematic diagram of a standard laser application.

FIG. 2 is a diagram showing an absorption spectrum of a light-absorbing layer according to an embodiment of the present invention.

Detailed Description

A schematic diagram of a standard laser application is shown in fig. 1. A laser medium 3 as a phosphor is excited by excitation light 2 of the laser diode 1, optically amplified in a resonator sandwiched by opposing high-reflectance mirrors 4, 4', and then emitted as laser light 5. At this time, the end face of the laser medium 3 becomes a reflection surface, and a parasitic oscillation 6 in which laser oscillation occurs in a direction different from the surface formed by the mirrors 4 and 4' is generated. When the parasitic oscillation 6 occurs, the output is reduced as compared with the laser beam predicted from the resonator originally constituted by the opposing mirrors 4, 4', and therefore it is required to prevent this.

In order to prevent the parasitic oscillation 6, a light absorption layer 7 is formed around the laser medium (core), and the light absorption layer 7 has a refractive index equivalent to that of the core and absorbs light in an oscillation wavelength band of the laser medium. As the light absorbing layer 7, it is known that Cr: YAG, Sm: YAG or the like is bonded to the laser medium 3 to prevent parasitic oscillation 6. However, these transition metal-doped YAG single crystals have a melting point as high as 1970 ℃, and the production cost is high when crystals are grown from a liquid phase. Further, although YAG polycrystal has a lower synthesis temperature than single crystal and can prevent impurities from being mixed, it requires a special apparatus, and thus, it is difficult to manufacture the YAG polycrystal.

Since YAG crystals have high hardness, a large amount of energy needs to be input for polishing, and since YAG needs to be heated to a high temperature even in thermal bonding, it is difficult to produce a composite with a laser medium. In addition, in recent years, development of laser media for use in high power applications has been reported in addition to YAG, but these laser media have high melting points and high hardness, and therefore, have problems of manufacturing cost and difficulty in processing, as with YAG materials. In view of such circumstances, as an absorption layer material for parasitic oscillation, a material that is easy to manufacture and easy to process for manufacturing a composite body has been studied instead.

The present inventors have conducted intensive studies on alternative materials and as a result, have obtained the following findings. Since glass has additivity between physical properties constituting raw materials, it is possible to continuously adjust the refractive index and the thermal expansion coefficient depending on the raw material ratio, and the optical absorption spectrum of metal ions in glass changes mainly depending on the coordination state of surrounding anions, it is also possible to finely adjust the optical absorption spectrum depending on the glass system, and further, since glass has high formability, it is easy to process into an arbitrary shape, and it is easy to bond with a laser light emitting element (laser medium), and thus, it is an effective finding to obtain a glass material as a light absorbing material for preventing parasitic oscillation.

In view of the above-described findings, an embodiment of the present invention is a light-absorbing layer that is joined to a laser medium to form a joined body, the light-absorbing layer including a glass material and having an oscillation wavelength of the laser medium (a wavelength of 650nm or more and less than 1400nm) of 0.1cm^-1～10.0cm^-1The difference between the refractive indexes of the light absorbing layer and the laser medium is within ± 0.1, and the difference between the linear thermal expansion coefficients of the light absorbing layer and the laser medium is within ± 1 ppm/K. Hereinafter, the laser medium may be referred to as a core and the light absorbing layer may be referred to as a cladding.

The glass material is a transparent material containing silicate as a main component, and examples thereof include alkali metal silicate glass materials, aluminosilicate glass, borosilicate glass, germanosilicate glass, and the like. By adding (doping) a transition metal element to these glass materials, the glass materials can be made to have light absorption in any range from visible light to infrared light bands. That is, the absorption spectrum corresponding to the oscillation wavelength of the laser light can be tuned. In addition, such doping of the absorbing element can also have light absorption at the laser oscillation wavelength with little change in physical properties such as the refractive index and the thermal expansion coefficient of the glass material as the base.

The light absorption layer of the embodiment of the present invention has a thickness of 0.1cm at a laser oscillation wavelength of 650nm or more and less than 1400nm^-1～10.0cm^-1The absorption coefficient of (2). Cr as a conventional light absorbing layer: the absorption coefficient of YAG at the laser oscillation wavelength (wavelength: 1030nm) was 2.0cm^-1～4.0cm^-1(typical value) if the absorption coefficient is 0.1cm^-1As described above, the light absorbing layer can be used to prevent parasitic oscillation. The absorption coefficient is preferably 2.0cm^-1Above, more preferably 3.0cm^-1Above, more preferably 4.0cm^-1The above.

Fig. 2 shows an absorption spectrum of a light-absorbing layer according to an embodiment of the present invention, and Cr: absorption spectrum of YAG. As shown in fig. 2, in the case of an Nd: YAG and Yb: YAG, Nd, YVO₄Exhibits an emission wavelength of Cr: YAG high absorption coefficient. Further, it is known that laser crystals other than YAG (Ti-sapphire, Cr-forsterite) also exhibit a high absorption coefficient.

The light-absorbing layer according to the embodiment of the present invention is characterized in that the difference between the refractive index of the light-absorbing layer and the refractive index of the laser medium (core) is within ± 0.1 and the difference between the linear thermal expansion coefficients of the light-absorbing layer and the laser medium (core) is within ± 1ppm/K at the laser oscillation wavelength of 650nm or more and 1400nm or less. For example, when Nd: YAG as core, Nd: YAG has a refractive index of 1.82 (wavelength: 1064nm) and a linear thermal expansion coefficient of 8ppm/K, and therefore the refractive index of the light-absorbing layer of the embodiment of the present invention is in the range of 1.72 to 1.92 and the thermal expansion coefficient is in the range of 7ppm/K to 9 ppm/K. Within this range, parasitic oscillation can be effectively prevented with little change in the physical property value of the base material.

The metal element added to the glass material is preferably at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sb, Te, La, Sm, Gd, Dy, Tb, Lu and Bi. However, the optical properties and the like described above are not always achieved by adding these elements, and the type and the amount of the metal element need to be appropriately adjusted in consideration of the type of the glass material as the base material, the desired absorption coefficient, and the like.

In a preferred embodiment of the present invention, a glass material having a melting point of 1500 ℃ or lower is preferably used. The melting point of the YAG material used as a conventional light absorbing layer is as high as 1970 ℃ or higher, and the production cost increases when crystals are grown from a liquid phase. On the other hand, the glass material can be synthesized in a short period of time (short time) by a melt quenching method or the like, and the production load can be reduced and the production cost can be reduced. Further, the Knoop hardness of YAG is about 1500kgf/mm²In contrast, the Knoop hardness of the glass material was about 500kgf/mm²～700kgf/mm²The processing load can be reduced.

In a preferred embodiment of the present invention, a glass material is partially crystallized to form a glass-crystal composite. This makes it possible to add the thermal conductivity characteristic of the crystal to the basic properties of the glass. In addition, glass materials have advantages that the amount of dopant dissolved in solid solution is large and the amount of dopant added can be easily adjusted, as compared with single crystals or polycrystalline YAG. In addition, a glass material (clad) can be bonded to the core material regardless of whether the core material is single crystal or polycrystalline.

Next, an example of a method for producing the light absorbing layer (cladding layer) according to the embodiment of the present invention will be described below.

Raw materials of titanium oxide, silicon oxide, sodium carbonate and metal elements to be added as raw materials of the glass material were weighed and mixed. The mixing can be carried out by a usual mixing method, and for example, it can be carried out for about 15 minutes using a mortar or the like. Next, the mixed powder is put into a crucible, decarbonated at a temperature of 100 ℃ or lower using an electric furnace or the like, and then melted. The melting temperature and the melting time are preferably adjusted depending on the viscosity of the melt. For example, the melting may be performed at a temperature in the range of 1200 to 1500 ℃ for 1 to 3 hours. In addition, a platinum crucible, an alumina crucible, or the like can be used as the crucible. Then, the melt was taken out of the furnace and quenched. It is preferable to remove strain by annealing at the glass transition temperature after quenching. By the above method, the clad layer serving as the light absorbing layer can be produced.

In addition, as a method of bonding a glass material (clad) to a laser medium (core), a bonding surface between a side surface portion of the core and the clad may be roughened, and then heated at a temperature of not lower than the glass transition temperature while applying pressure, thereby performing thermal bonding. Alternatively, the joining may be performed by partially roughening the side surface of the core, then introducing it into an electric furnace together with a casting mold, and pouring the molten glass material in another electric furnace.

The evaluation methods including examples and comparative examples can be as follows.

(concerning absorption coefficient)

Evaluation was performed using a two-beam spectrophotometer (UV-3600 Shimadzu Co., Ltd.).

(with respect to refractive index)

Derived from the reflectance using a spectroscopic ellipsometer (M-2000 j.a.woollam).

(regarding thermal expansion coefficient)

The measurement was carried out using a Thermomechanical analysis (TMA: Thermomechanical Analyzer) apparatus (TMA8310 chem Co.).

Examples

The following description will be made based on examples and comparative examples. It should be noted that this embodiment is only an example, and is not limited in any way by this example. That is, the present invention is limited only by the claims and includes various modifications other than the examples included in the present invention.

For reference, conventional Cr is shown below: YAG (cladding). Cr: YAG has a melting point of 1970 ℃ and an absorption coefficient of 3.5cm^-1(wavelength: 650 nm-1400 nm), refractive index of 1.82, and thermal expansion coefficient of 7.8 ppm/K. Further, when Nd: in the case of YAG as a laser medium (refractive index: 1.82, thermal expansion)Rate: 8ppm/K), the difference of the refractive indexes is less than 0.01, and the difference of the thermal expansion coefficients is almost zero.

(examples)

Titanium oxide, silicon oxide, sodium carbonate and nickel oxide as raw materials of the glass material were weighed and mixed. Subsequently, the mixed powder was decarbonated at 800 ℃ and then melted at 1300 ℃ for 1 hour, and then taken out of the furnace and quenched. After quenching, annealing was performed at 600 ℃ to remove strain, thereby producing a Ni-doped titanosilicate glass (melting point: 1300 ℃). The characteristics of the obtained glass (clad layer) were evaluated, and as a result, the absorption coefficient was 5.0cm^-1(wavelength: 650 nm-1400 nm), refractive index of 1.83 (wavelength: 1064nm), and thermal expansion coefficient of 7 ppm/K. Further, when Nd: when YAG was used as the laser medium (refractive index: 1.82, thermal expansion coefficient: 8ppm/K), the difference in refractive index was 0.01 and the difference in thermal expansion coefficient was 1, and the results were equal to or more than those of the conventional one. In addition, with Cr: YAG (cladding layer) is easier to process for producing a composite.

Industrial applicability

The present invention relates to a light absorbing layer for preventing parasitic oscillation of a laser oscillator/amplifier, and has an excellent effect that manufacturing cost can be suppressed and processing for producing a joined body of the light absorbing layer and a laser medium can be easily performed. The light-absorbing layer and the joined body of the present invention are useful for laser applications such as high-power lasers (amplifiers).

Description of the reference symbols

1 laser diode

2 exciting light

3 laser medium (core)

4 reflecting mirror

5 laser

6 parasitic oscillation

7 light absorbing layer (clad)