JP2014040350A - Optical ceramics and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily roughen a surface of an optical ceramic material without using etching.SOLUTION: A part of a surface of an optical ceramic material is roughened with an abrasive; the optical ceramic material after roughened is heat treated to eliminate microcracks produced by roughening while maintaining the roughened state; and another part of the surface of the optical ceramic material is subjected to optical polishing to form a mirror surface. Thus, the surface of the optical ceramic material can be easily roughened without using etching.

Description

  The present invention relates to roughening of optical ceramics such as laser rods.

The applicant has succeeded in producing polycrystalline optical ceramics having a light transmission equivalent to that of a single crystal. For example, Patent Document 1 (JP4878343B) discloses a method for producing a transparent rare earth gallium garnet (Ln ₃ Gd ₅ O ₁₂ : Ln is a rare earth element). Patent Document 2 (JP2003-20288A) disclosed a method for producing a transparent rare earth aluminum garnet (Ln ₃ Al ₅ O ₁₂ ). By the way, not all surfaces of optical ceramics are desired to be transparent, but it may be desired to make some surfaces rough and opaque. For example, in the case of a laser rod, it is desired to roughen the side surface to prevent parasitic oscillation.

  Patent Document 3 (JPS63-211779A) describes a microcrack caused by roughening by wrapping Nd-doped laser glass with 1000 mesh alumina particles to roughen the surface and then chemically etching to a depth of 100 μm. Is disclosed. Lapping means that the abrasive is dispersed in the liquid, the liquid in which the abrasive is dispersed is placed between the surface to be polished and the base, and polishing is performed by relative movement between the surface to be polished and the base. To do. Patent Document 3 describes that by removing microcracks by etching, the laser glass is not broken even when the laser is operated at a high output.

  However, when chemical etching is performed on ceramics, etching to the grain boundary precedes the removal of microcracks, and grain breakage occurs in the particles on the rough surface portion. Thereby, the problem that the smoothness of the surface becomes good occurs. In the experiments by the inventors, when the side surface of the polycrystalline ceramic Nd-YAG laser rod was roughened and then etched, the surface roughness Ra was as small as about 0.2 μm. The surface roughness is effective from 0.3 μm or more, preferably 0.5 μm or more. Moreover, since chemical etching is a process different from the normal manufacturing process of ceramics, the introduction of an etching process is a burden for ceramic manufacturers. It is also difficult to select appropriate etching conditions.

JP4878343B JP2003-20288A JPS63-211779A

  An object of the present invention is to roughen the surface of an optical ceramic without using etching.

  The optical ceramic of the present invention is made of a polycrystalline sintered body. After a part of the surface is roughened with an abrasive, the microcracks are removed by heat treatment, and the surface grains become convex. ing.

In the method for producing an optical ceramic of the present invention, a step of producing an optical ceramic comprising a polycrystalline sintered body by molding and sintering a powder;
A step of roughening a part of the surface of the optical ceramic with an abrasive;
The step of heat-treating the optical ceramic after the roughening to remove the microcracks caused by the roughening and to make the surface grains convex while keeping a part of the surface rough; The process of mirror-polishing the other part of the surface is performed in this order.

  In the present invention, microcracks are eliminated not by chemical etching but by heat treatment. Therefore, neither etching equipment nor etching conditions need to be selected, and there is no need to handle a corrosive etching solution. In this specification, the description relating to the method for producing optical ceramics also applies to optical ceramics as they are. As the polishing agent, alumina, SiC, diamond or the like is used, and sandblasting, pressing of the polishing agent, roughening by polishing with a sheet to which the polishing agent is attached, etc., and sandblasting and pressing of the polishing agent are particularly preferable.

  Preferably, the optical ceramic is a rare earth aluminum garnet, a rare earth gallium garnet, or a rare earth oxide, roughened with an abrasive having an average particle size of 20 μm or more, and heat-treated at 1300 ° C. or higher and 1700 ° C. or lower. In this specification, the surface roughness of the roughened surface is represented by an arithmetic average surface roughness Ra. The surface roughness Ra is generally smaller than the average particle size of the abrasive, and in order to make Ra 1 μm or more, in the case of garnet or rare earth oxide containing rare earths, an abrasive with an average particle size of 20 μm or more is required. It is. In the case of garnet or rare earth oxide having rare earth as a constituent element, the temperature at which atoms freely move on the surface of the ceramic (the temperature at which thermal etching starts) is suitable for the heat treatment temperature, and this temperature is 1300 ° C. or higher. On the other hand, when the heat treatment temperature exceeds 1700 ° C., the effect of roughening may be lost. In this specification, the rare earth includes Y.

  Particularly preferably, an abrasive having an average particle size of 30 μm to 300 μm is roughened by sandblasting or pressing the surface of the optical ceramic, and heat treatment is performed in vacuum or in hydrogen at 1300 ° C. to 1500 ° C. At this time, the roughened surface grain is convexed into a hemisphere. Thereby, a rough surface can be formed more finely in a portion roughened by sandblasting or pressing, and roughening can be performed more efficiently. The surface roughness Ra can be roughened to about 1.5 to 3 μm by sandblasting or pressing an abrasive with an average particle size of 30 μm to 300 μm on the surface of rare earth aluminum garnet, rare earth gallium garnet or rare earth oxide ceramics. Microcracks can be eliminated by setting the temperature to 1300 ° C to 1500 ° C.

The perspective view of the laser rod of an Example Side view of the laser with partial cutout of the embodiment Characteristic diagram showing the surface roughness of the roughened portion in the laser rod of the example Characteristic diagram showing the surface roughness of the roughened part of the modified laser rod Electron micrograph of the roughened portion of the laser rod of the example

  Although the optimal example for implementing this invention is shown below, this invention is not restrict | limited to an Example, Example can be changed according to well-known techniques, such as patent document 1, and those well-known to those skilled in the art.

  1 to 5 show an embodiment. FIG. 1 shows the shape of the laser rod 2, which has a round bar shape, both end surfaces of which are mirror surfaces 4 and 4, and the side surfaces thereof are rough surfaces 6. A part of the side surface may be roughened instead of the entire side surface. Further, the optical ceramics are not limited to the laser rod 2, but may be a disk shape, a prism shape, a lens shape, or the like. Applications of optical ceramics are not limited to laser media. The laser rod 2 is made of, for example, Nd-YAG polycrystalline ceramics, 1 atm% of Y atoms are replaced with Nd atoms, the average particle diameter of the ceramics is, for example, 1.3 μm, and the firing conditions are, for example, a maximum firing temperature of 1800 ° C. in vacuum. is there. The rough surface 6 requires Ra of at least 0.3 μm, for example, 0.5 μm or more, preferably 1 μm or more. In order to increase Ra to more than 5 μm, it is necessary to increase the particle size of the abrasive. This causes deep cracks in the laser rod 2 during sandblasting, pressing of the abrasive, etc., so Ra is preferably 5 μm or less. Ra is, for example, from 0.3 μm to 5 μm, preferably from 0.5 μm to 5 μm, particularly preferably from 1 μm to 3 μm.

  FIG. 2 shows a laser 10, an excitation light source 14 such as an Xe lamp or an LED is disposed facing the laser rod 2, the laser rod 2 and the excitation light source 14 are disposed in a container 14 having an inner surface as a reflection surface, The resonant mirrors 16 and 18 are arranged so as to face the mirror surfaces 4 and 4. The resonant mirror 16 is for total reflection, and the resonant mirror 18 is for partial reflection, and outputs a part of light as a laser beam.

An example of manufacturing the laser rod 2 will be shown. In accordance with Patent Document 2, YAG polycrystalline optical ceramics were produced. In an aqueous solution containing yttrium nitrate, aluminum nitrate and neodymium nitrate (Y: Al: Nd is a molar ratio of 297: 500: 3), colloidal silica (as SiO ₂ is 0.04 wt% with respect to 100 wt% of Y ₃ Al ₅ O ₁₂ ), Urea and concentrated sulfuric acid were added, and the mixture was precipitated at 100 ° C. with stirring. Filtration and washing were repeated to obtain a YAG raw material powder. Note that 1 atm% of Y is replaced with Nd. A dispersion medium and a binder were added to the raw material powder, molded into a rod shape with a diameter of 4 mm and a length of 12 mm, degreased at 1100 ° C., and fired in vacuum at 1800 ° C. for 10 hours to obtain an optical ceramic. This ceramic had an average particle diameter of 1.3 μm when the fracture surface was observed with a microscope.

  The surface of the ceramic was roughened by sandblasting or pressing an abrasive. Next, heat treatment was performed in vacuum so as to maintain the maximum firing temperature for 1 hour to remove microcracks associated with roughening. Change to vacuum or use hydrogen. After firing, both end faces of the ceramic were mirror-polished to a surface roughness Ra = 0.1 to 0.5 nm and a flatness = λ / 10 (λ = 633 nm) to obtain a laser rod 2 shown in FIG. Table 1 shows the surface roughness of each sample and the performance as a laser rod. The data of the surface roughness meter of sample 1 is shown in FIG. 3 (vertical magnification 2800 times), and the data of the surface roughness meter of sample 3 is shown in FIG. 4 (vertical magnification 1400 times). An electron micrograph of the surface of Sample 1 is shown in FIG. It can be seen that the entire scale of FIG. 5 is 50 μm, large irregularities are generated on the surface of the ceramic by roughening, and the grains on the surface are convex in a hemispherical shape.

  In the table, alumina 170 μm or the like indicates the abrasive used and its average particle diameter, and 0.3 W in the laser oscillation performance indicates the output of the excitation light source that becomes the laser oscillation threshold. 24.8% or the like indicates the slope efficiency when the output of the excitation light source is increased from the oscillation threshold, which is an increase in the oscillation output per increase of the excitation light source output. Moreover, 14W etc. show the maximum output in the single mode, and 40W etc. show the maximum output in the multi mode. For the sample 5 in which the heat treatment column is ..., only the roughening treatment was performed, and no heat treatment was performed. In Sample 6, the roughened side surface was etched at 170 ° C. for 120 minutes using an etching solution of 1: 1 mixture of concentrated sulfuric acid and concentrated phosphoric acid.

  When chemical etching was performed after roughening, the roughened surface was smoothed to Ra of 0.2 μm, and along with this, the slope efficiency and maximum output in laser oscillation decreased. In addition, when only the surface roughening was performed and the heat treatment was not performed, the surface grain did not become convex, and the slope efficiency and maximum output in laser oscillation were slightly reduced. On the other hand, when the heat treatment was performed after the roughening, the surface grains became hemispherical. For this reason, the surface of the ceramic was greatly roughened by sand blasting or the like, and the structure was further finely roughened by the grain convexity. Even when heat treatment was performed after roughening, the surface roughness Ra basically remained as it was during roughening. The best results were obtained in terms of slope efficiency and maximum output performance in laser oscillation. Further, since the heat treatment can be performed in a baking furnace, no additional equipment is required. Furthermore, unlike chemical etching, heat treatment does not generate toxic vapors or use corrosive liquids. When the surface roughened by sandblasting, pressing of an abrasive or the like was heat-treated, the laser rod was not chipped during subsequent mirror polishing or cracked during oscillation at the maximum output.

2 Laser rod 4 Mirror surface 6 Rough surface 10 Laser 12 Excitation light source 14 Container 16, 18 Resonant mirror

Claims (5)

  An optical ceramic comprising a polycrystalline sintered body, wherein a part of the surface is roughened with an abrasive and then microcracks are removed by heat treatment, resulting in convexity of the surface grain. .   Optical ceramics are rare earth aluminum garnet, rare earth gallium garnet, or rare earth oxide, roughening is performed with an abrasive having an average particle size of 20 μm or more, and heat treatment is performed at a temperature of 1300 ° C. to 1700 ° C. The optical ceramic according to claim 1, wherein: A process for producing optical ceramics comprising a polycrystalline sintered body by molding and sintering powder;
A step of roughening a part of the surface of the optical ceramic with an abrasive;
A step of heat-treating the optical ceramic after the roughening to remove the microcracks caused by the roughening and to make the surface grains convex while keeping a part of the surface rough;
A method for producing an optical ceramic, wherein the other part of the surface of the optical ceramic is mirror-polished in this order.   The optical ceramic is a rare earth aluminum garnet, a rare earth gallium garnet or a rare earth oxide, characterized by roughening with an abrasive having an average particle size of 20 μm or more, and heat-treated at 1300 ° C. or more and 1700 ° C. or less. The manufacturing method of the optical ceramics of Claim 3.   The surface-roughening is performed by blasting or pressing an abrasive having an average particle size of 30 μm to 300 μm against the surface of the optical ceramic, and heat treatment is performed in vacuum or in hydrogen at 1300 ° C. to 1500 ° C. 4. Manufacturing method of optical ceramics of 4.