JPH02262385A - Wavelength conversion type solid laser and its manufacture - Google Patents

Abstract

PURPOSE:To facilitate the generation of a laser beam and to contrive the simplification of the constitution of the title laser and a reduction in the size of the laser by a method wherein an impurity to excite the laser beam is doped to at least one side of a waveguide part and a clad part by light irradiation, the generation of the fundamental wave of the laser beam is performed by an external excitation and this wave is simultaneously converted its wavelength to generate the short-wavelength laser beam. CONSTITUTION:First, a semi-circular recessed part 22 is provided in the central part of the upper surface of a flat plate 21 consisting of a nonlinear optical material. The plate 21 having this recessed part 22 is dipped into a solution, in which KPO3 is used as a basic flux and 7 molar % of Nd is contained to the amount of the KPO3 as a light excitation impurity. This solution is cooled for two days at the rate of 1 deg.C/day from 900 deg.C, for example, and a KXRb1-XTiOPO4 thin film 23 containing the Nd as an impurity is grown and formed on the plate 21. Then, the film 23 is etched by a chemical etching method or the like and the film 23 is left only on the recessed part 22. A growth of KTP is further performed on the plate 21. Hereafter, a light emitting part of a clad part 12 is processed according to the need. Moreover, a mirror processing is performed on the end face of a waveguide part 11.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a wavelength conversion optical element for obtaining a short wavelength light source used in optical information processing, photometer n1, etc. This invention relates to a wavelength-converting solid-state laser that generates laser light through excitation.

(Prior Art) In recent years, short-wavelength coherent light sources have been developed for application to high-density optical disk systems, measurement and display systems, and the like.

In an optical disk system, the spot diameter of the light focused on the disk surface is proportional to the wavelength of the light source, so a short wavelength light source is essential to achieve high density. As a short-wavelength light source, semiconductor lasers have the advantages of being small, lightweight, and low power consumption, so the development of short-wavelength lasers using new materials is progressing, and the oscillation wavelength is already in the 0.6 μm band (red). InGaAIP-based semiconductor lasers with the following characteristics have reached the level of practical use. However, although research has been carried out on green or blue lasers with shorter wavelengths, a laser that continuously oscillates at room temperature has not been obtained, and there is still no prospect of practical use.

On the other hand, as another means of realizing a short wavelength light source, there is optical second harmonic generation (SHG) using a nonlinear optical crystal.
More research has been conducted than ever before. In order to realize compactness and low power consumption, attempts have been made to use a semiconductor laser as a fundamental wave light source and to turn a nonlinear optical crystal into a waveguide. For example, proton exchange LiNb0 as shown in Fig.
．． Using a waveguide, a 1 mW blue light source has been obtained as the optical second harmonic of an 80 mW semiconductor laser (Noh Taniuchi:
Autumn 1986 Japan Society of Applied Physics, 19p-ZG-4 (1
987)) In the figure, 41 is a mount, 42 is a semiconductor laser, 43 is a 1/2 wavelength plate, 44 is a condensing lens, 4
5 indicates a LiNBOi optical waveguide, and 46 indicates blue SHG light. This method uses Cerenkov radiation to radiate optical second harmonics into the waveguide substrate.
This method has the advantage of not requiring phase matching through angle control or temperature control.

However, the example shown in FIG. 4 requires a fundamental wave incident light source and a plurality of condensing lenses, making the device structure complicated and difficult to make compact. Furthermore, it is necessary to accurately input the fundamental wave into the leading waveguide, making it necessary to adjust the optical path, and the problem remains that the structure becomes increasingly large.

(Problems to be Solved by the Invention) As described above, in the conventional SHG that uses Cerenkov radiation that does not require phase matching, it is necessary to accurately input the fundamental wave into the waveguide. For this reason, it is necessary to collect the fundamental wave at the incident end and to perform more precise positioning, resulting in a problem that the structure becomes complicated and large.

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to easily generate a short wavelength laser beam by wavelength conversion, and to obtain a wavelength that can simplify and miniaturize the configuration. An object of the present invention is to provide a conversion solid-state laser and a method for manufacturing the same.

[Structure of the Invention (Means for Solving the Problems) The gist of the present invention is to omit the fundamental wave incidence mechanism in a Cerenkov radiation type wavelength conversion element and to arrange the fundamental wave generation part in the leading wave path. be.

That is, the present invention provides an optical waveguide type wavelength set in which at least one of the waveguide part and the cladding part is formed of a nonlinear optical material, and the fundamental wave is set in the waveguide mode and the optical second harmonic is set as Cerenkov radiation light. This is a wavelength conversion solid-state laser that consists of a conversion optical element and has impurities added to at least one of the waveguide part and the cladding part to excite the laser beam by light irradiation, and generates a fundamental wave by external excitation. It converts the wavelength and generates short wavelength laser light.

The present invention also provides a method for manufacturing a wavelength conversion solid-state laser, in which a recess is provided in a straight line on the surface of a flat plate that becomes a part of a cladding part of a waveguide type wavelength conversion element, and then a wavelength conversion A thin film doped with impurities that becomes the waveguide of the device and excites the laser beam when irradiated with light is formed, then this thin film is etched, leaving the thin film only in the recesses of the flat plate, and then the wavelength conversion element is placed on the flat plate. This method forms a thin film that becomes part of the cladding part.

(Function) According to the present invention, it is possible to create an element that simultaneously has an optical waveguide based on the Cherenkov radiation method and a laser generating section that generates a fundamental wave, and the laser beam generated by the laser generating section can be optically guided. It is possible to output short wavelength laser light by converting the wavelength in the wave path. Therefore, a lens, a precision adjustment mechanism, etc. for inputting an incident wave into an optical waveguide, which were conventionally necessary, are no longer necessary, and it becomes possible to obtain a compact short-wavelength solid-state laser.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a sectional view showing a schematic configuration of a wavelength conversion solid-state laser according to an embodiment of the present invention.

In the figure, reference numeral 11 denotes a waveguide section made of a nonlinear material doped with, for example, Nd, and this waveguide section 11 is covered with a cladding section 12 made of a nonlinear optical single crystal.

Here, the cross-sectional shape of the waveguide section 11 is circular, and the cross-sectional shape of the cladding section 12 is rectangular.

Since the waveguide section 11 contains a large amount of laser excitation impurities (for example, Nd), upon irradiation with the external excitation light 13, it emits a laser beam (fundamental wave) 14 with a wavelength of about 1 μm. At the same time, an optical second harmonic 15 (green laser with a wavelength of about 0.5 μm) relative to the laser beam 14 is generated in the cladding 12 .

The laser beam 14 is outputted as a fundamental wave 16 from the end of the mirrored waveguide section 11 .

Further, the optical second harmonic 15 is output from the end of the cladding section 12 as short wavelength light 17.

Next, a method for manufacturing the laser shown in FIG. 1 will be explained with reference to FIG. 2.

First, as shown in Fig. m2 (a), a semicircular recess 22 is provided in the center of the upper surface of a flat plate 21 of a nonlinear optical material, for example, KT P (KT i OP 04 ). Next, the flat plate 21 having the recesses 22 is immersed in a solution containing KPO as a basic flux.

In this solution, considering the refractive index, RbPO3, KPO,
The content is 3 to 5 mol%.

Furthermore, Nd was added as a photoexcited impurity to KPO,
The mole percentage is included. The solution was heated from 900°C to 1°C/da
y for two days, and as shown in FIG. 2(b), KxRb containing Nd as an impurity is placed on the flat plate 21,
A thin film 23 of xT i OPO is grown. At this time, by providing the recesses 22 in the flat plate 21, a large amount of the segregated impurity Nd is added to the layer grown in the recesses 22.

Next, the thin film 23 is etched by a chemical etching method or the like, leaving the thin film 23 only on the recess 22 as shown in FIG. 2(C). This remaining thin film 23 has a circular cross section, which constitutes the waveguide section 11. Next, for the purpose of improving the extraction efficiency of the optical second harmonic, KTP is further grown on the flat plate 21 to create a structure as shown in FIG. 2(d). This allows the waveguide section 11 to be connected to the cladding section 1.
The structure shown in FIG. 1 coated with 2 is realized. After this, the light emitting portion of the cladding portion 12 is processed as necessary. Further, the end face of the waveguide section 11 is mirror-processed.

When the wavelength-converting solid-state laser thus obtained is irradiated with excitation light 13, the Nd-doped waveguide 11 has a wavelength of about 1μ.
m laser beams 14 are generated, and this laser beams 14 are emitted from the end face of the waveguide section 11. At this time, the excitation light 13 may be irradiated from a direction perpendicular to the waveguide 11 as shown in FIG. 1, or may be irradiated onto the end face of the waveguide 11. On the other hand, the optical second harmonic 15 output from the waveguide section 11 to the cladding section 12 as Cherenkov radiation is emitted from the end face of the cladding section 12. This makes it possible to simultaneously obtain the fundamental wave 16 with a wavelength of about 1 μm and the green laser beam 17 with a wavelength of about 0.5 μm from the end face of the laser of this embodiment.

As described above, according to this embodiment, it is possible to generate short wavelength laser light (green) by simply irradiating the waveguide section 11 with excitation light, and in this case, the laser light source and the waveguide are connected as in the prior art. No alignment required. Therefore, an optical system for positioning is not required, and the configuration can be simplified and downsized. Further, the excitation light is not limited to laser light, but may be white light from a lamp or the like, so it is highly versatile. Furthermore, it has the advantage that it can be realized with a simple configuration simply by adding Nd to the waveguide of a conventional waveguide type wavelength conversion element.

FIG. 3 is a sectional view showing a schematic configuration of another embodiment of the present invention. The same parts as in Fig. 1 are given the same reference numerals.
A detailed explanation thereof will be omitted.

This embodiment differs from the previously described embodiments in that the light emitting end face of the cladding portion is tapered to obtain parallel light. That is, the light emitting end face of the cladding part 12 is provided with a taper that becomes narrower on the end face side, and the second harmonic of the light 15
The angle of the taper is set so that the optical second harmonic 37 emitted from the end face becomes parallel light based on the relationship between the wavelength and the refractive index of the cladding part 12.

As a method for forming this taper, for example, the end surface side to be tapered may be immersed in an etching solution and gradually pulled up. As the pulling speed increases, the taper angle θ increases, and as the pulling speed decreases, the taper angle θ decreases. Furthermore, by varying the pulling speed, the tapered portion can have a curvature, which also makes it possible to focus the optical second harmonic 37.

With such a configuration, not only can the same effects as in the previous embodiment be obtained, but also there is an advantage that the optical second harmonic can be output as parallel light. If it is parallel light, it is easy to focus it with a normal lens or the like, which increases its versatility for various uses.

Note that the present invention is not limited to the embodiments described above. For example, instead of adding laser-excited impurities to the waveguide section, laser-excited impurities may be added to the cladding section.

Furthermore, laser excitation impurities may be added to both the waveguide section and the cladding section. Further, the laser excitation impurity is not limited to Nd, and other materials can be used. Furthermore, in the embodiment shown in FIG.
Although the harmonics are output as parallel light, it is also possible to output the optical second harmonics as focused light or spherical waves depending on the shape of the light output end face of the cladding part. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, at least one of the waveguide portion and the cladding portion is doped with an impurity that excites the laser beam by light irradiation, and the fundamental wave is generated by external excitation. Since this is wavelength-converted at the same time to generate short-wavelength laser light, short-wavelength laser light can be easily generated by wavelength conversion, and the configuration can be simplified and miniaturized. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a wavelength conversion solid-state laser according to an embodiment of the present invention, FIG. 2 is a perspective view showing the manufacturing process of the laser, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a $1=1 diagram showing the schematic structure of the conventional device. 11... Waveguide part 12... Clad part 13... Excitation light 14.16... Fundamental wave 15.17.37... Optical second harmonic (short wavelength light) 21
... Flat plate 22 ... Part 4 23 ... Thin film applicant's agent Patent attorney Suzue Takehiko 1E3j! 1

Claims (3)

[Claims] (1) Optical waveguide-type wavelength conversion optics in which at least one of the waveguide part and the cladding part is formed of a nonlinear optical material, and the fundamental wave is set in the waveguide mode and the optical second harmonic is Cherenkov radiation light. It consists of an element in which at least one of the waveguide section and the cladding section is doped with an impurity that excites the laser beam by light irradiation, generates a fundamental wave by external excitation, and converts the wavelength of this fundamental wave to produce a shorter wavelength. A wavelength-converting solid-state laser that generates laser light. (2) The wavelength converting solid-state laser according to claim 1, wherein the end face shape of the light emitting side of the cladding portion has a tapered shape that converts a circular wave into a plane wave or a spherical wave. (3) A step of providing a linear concave portion on the surface of a flat plate that will become a part of the cladding portion of an optical waveguide type wavelength conversion element, and a step of forming a concave portion on the flat plate to become a waveguide portion of the wavelength conversion element and emitting laser light by light irradiation. a step of forming a thin film doped with an impurity that excites a A method of manufacturing a wavelength conversion solid-state laser, comprising: