JPH04128805A - Optical waveguide element - Google Patents

Abstract

PURPOSE:To prevent sublimation or transformation by depositing a transparent optical plane plate by optical contact on the end face of the element including the end face of a waveguide part the shutting off the end face of the waveguide part and the ambient atmosphere. CONSTITUTION:A DMNP 11' is maintained in a molten state in a furnace, etc., and one end of a glass fiber 12' is immersed therein. The DMNP 11' is then infiltered into the hollow part by capillarity. The glass fiber 12' is there after rapidly cooled and further this glass fiber 12' is gradually drawn from the inside of the furnace kept at the temp. higher than the m. p. of the DMNP 11' to the outside of the furnace kept at the temp. lower than the m. p., by which the DMNP 11' in the molten state is crystallized to a single crystal from the part drawn out of the furnace. Both end faces of the glass fiber 12' are thereafter polished to the surface accuracy to the extent of allowing the optical contact. The optical plane plates 13a, 13b made of the SF 10 glass formed to the disk shape of nearly the same diameter as the diameter of the glass fiber 12' are respectively brought into contact with each other in such a manner that foreign matter, such as dust, moisture and air, does not enter therebetween.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an optical waveguide element having a waveguide section made of an organic material, and more specifically, an optical waveguide element that is capable of preventing sublimation or metamorphosis of the organic material. This invention relates to optical waveguide devices.

(Prior Art) Various attempts have been made to convert the wavelength of laser light into a second harmonic or the like (shorten the wavelength) using nonlinear optical materials. A so-called fiber type device has been proposed as one type of optical wavelength conversion device that performs wavelength conversion in this manner. This optical wavelength conversion element is an optical fiber whose cladding is filled with a core made of a nonlinear optical material, and is published in Journal of the Micro-Optics Research Group of the Japan Society of Applied Physics Vol. 3. No, 2. An example is shown on pages 28-32. Since this fiber-type optical wavelength conversion element can easily achieve phase matching between the fundamental wave and the second harmonic, research on this fiber-type optical wavelength conversion element has been actively conducted recently. .

Also, for example, JP-A-63-15233, JP-A No. 6B-15
As shown in Japanese Patent No. 234, an optical waveguide type optical wavelength conversion element is also known in which an optical waveguide made of a nonlinear optical material is formed between two substrates serving as cladding layers. Furthermore, a three-dimensional optical waveguide-type optical wavelength conversion element is also known in which a three-dimensional optical waveguide made of a nonlinear optical material is embedded in a glass substrate and emits a wavelength-converted wave into the glass substrate. These optical waveguide type optical wavelength conversion elements also have the above-mentioned features.

Further, in Japanese Patent Application Laid-Open No. 1-2444:33, it is described in detail that the sum frequency and the difference frequency are similarly generated by a fiber type wavelength conversion element. Regarding generation of sum-difference frequency in a waveguide type optical wavelength conversion element, Japanese Patent Application Laid-Open No.
It is described in detail in JP-A-244434. Furthermore, third harmonic generation using third-order nonlinearity is also fully possible.

Incidentally, in recent years, various proposals have been made to use single-crystal organic nonlinear optical materials as nonlinear optical materials in these fiber type and optical waveguide type optical wavelength conversion elements.

Since this organic nonlinear optical material has a significantly larger nonlinear optical constant than inorganic materials, it is possible to obtain high wavelength conversion efficiency by using this organic nonlinear optical material. As this organic nonlinear optical material, for example, Japanese Patent Application Laid-Open No. 60-250334, 'Nonliner 0p
ticalProperties of Orga
nic and polymeric material
als”AC5SYMPO3IUM 5ERIES
223. Edited by David J. Willjams (
American Chemical 5oci
``Organic Nonlinear Optical Materials'' Masao Kato, Supervised by He Nakanishi (CMC Publishing Co., Ltd., 1985), ``Non1inear 0pti''
cal Properties of Organi
cMolecules and Crystals
” D, S, Chemla and J, Zyss
Edited by Academic Press Inc.

1987), “The Qualjty and Perform” by R.T., Balley et al.
anceorTheOrganic Non-Lin
ear 0ptical Material(-)
2- ((2-Methylbenzylamino)
-5-N1tropyridine (MBA-NP
) ” (Optics Coo+munieat
ions, Vol. 65. No.3,
MNA (2-methyl-4-
nitroaniline), mNA (metanitroaniline)
, POM (3-methyl-4-nitropyridine-1-oxide), urea, NPP [N-(4-nitrophenyl)-(S)-prolinol], NPAN (2-[N
-(4-nitrophenyl)-N-methylaminocoacetonitrile, DAN (2-dimethylamino-5-nitroacetanilide), MBA-NP [2-N (
α-Methylbenzylamino)-5-nitroalinco, and 3,5 shown in JP-A-62-210432.
-dimethyl-1-(4-nitrophenyl)pyrazole [
Hereinafter referred to as DMNP, 3,5-dimethyl-1-(
4-nitrophenyl)-1,2,4-triazole, 2
-ethyl-1-(4-nitrophenyl)imidazole,
1-(4-nitrophenyl)pyrrole, 2-dimethylamino 1-5-nitroacetanilide, 5-nitro-2-
Examples include pyrrolidinoacetanilide, 3-methyl-4-ditropyridine-N-oxide, and the like.

(Problems to be Solved by the Invention) However, in the fiber type or optical waveguide type optical wavelength conversion element obtained by constructing the core of an optical fiber or the optical waveguide using the above-mentioned organic nonlinear optical material, conventionally, The problem has been recognized that wavelength conversion efficiency and fundamental wave incident coupling efficiency deteriorate significantly over time.

In other words, the organic nonlinear optical material that constitutes the waveguide of the optical wavelength conversion element comes into contact with the surrounding air or other atmosphere at its end face, so it sublimes from this part, shortening the single crystal part, or metamorphosing and forming a single crystal part. This causes the above-mentioned problem because it is no longer a crystal.

Having explained the problems in optical wavelength conversion elements above, the problem of sublimation and metamorphosis of the waveguide part is not limited to optical wavelength conversion elements, but also in optical waveguide elements (including optical fibers) in which the waveguide part is made of organic material. , which can occur widely.

In view of the above points, the present applicant previously proposed providing a blocking layer on the end face of the element including the end face of the waveguide part to isolate the end face of the waveguide part from the surrounding atmosphere (for example, Japanese Patent Application No. 309
(See specification No. 145). Although this blocking layer is extremely effective in preventing the above-mentioned problems, even if it is provided, deterioration of the waveguide end face may still be observed.

Therefore, an object of the present invention is to provide an optical waveguide element that can more reliably prevent the problem of the deterioration of the waveguide section.

(Means for Solving the Problems) The optical waveguide device according to the present invention is of a fiber type, a two-dimensional optical waveguide type, or a three-dimensional optical waveguide type in which the waveguide portion is made of an organic material.
In a dimensional optical waveguide type optical waveguide element, a transparent optical flat plate is attached to the end face of the element, including the end face of the waveguide part, with an optical contact, and this optical flat plate connects the end face of the waveguide part to the surrounding atmosphere. It is characterized by being designed to block out.

(Function) If the above-mentioned optical flat plate is provided, the end face of the waveguide made of an organic material will not be in direct contact with the atmosphere such as air, thereby preventing the above-mentioned sublimation or metamorphosis.

Unlike conventional blocking layers, which are formed by applying a resin or the like to the element end face and then drying and solidifying it, the above-mentioned optical flat plate is made by freely selecting and using materials with high barrier properties, such as glass. Formable.

Therefore, in the above configuration, the shielding effect of the optical plane plate can be significantly enhanced, and sublimation and metamorphosis of the waveguide section can be more reliably prevented.

Furthermore, in the configuration of the present invention described above, it is possible to prevent deterioration of the end face of the waveguide that would otherwise occur when a conventional blocking layer is provided.

This point will be explained in detail below.

Most conventional blocking layers have been formed by coating various resins different from the organic material that constitutes the waveguide. In that case, according to research by the present inventors, the organic material at the end of the waveguide disappears due to diffusion or miscibility of the organic material into the resin etc. at the interface between the waveguide and the blocking layer. Sometimes.

On the other hand, in the optical waveguide device of the present invention, the optical plane plate is attached to the end face of the device by optical contact, so the above-mentioned problem does not occur.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

1 and 2 show an optical wavelength conversion element 1o which is an embodiment of the optical waveguide element of the present invention. This optical wavelength conversion element 1o is an optical fiber in which a core 11 made of a nonlinear optical material is filled in a hollow part at the center of a cladding 12. As the nonlinear optical material, an organic nonlinear optical material with high wavelength conversion efficiency is used as described above. In this example, in particular, the core 1 is
1 is formed. And core 1 consisting of this DMNP
Optical plane plates 13a and 13b are respectively adhered onto the element end faces 10a and 10b, including the end faces of the elements 1 and 1.

Here, - as an example, the core 11 is the above-mentioned D M N P
.

In the case where the cladding 12 and the plane plates 13a and 13b are made of 5FIO glass, this optical wavelength conversion element 1
The manufacturing method of 0 will be explained.

First, a hollow glass fiber 12' that becomes the cladding 12
will be prepared. This glass fiber 12' has, for example, an outer diameter of about 1 mm and a hollow diameter of about 1 μm. Then, as shown in FIG. 3, DMNPII' is kept in a molten state in a furnace or the like, and one end of the glass fiber 12' is penetrated into this melt. Then, DMNPII' in a molten state enters the hollow portion of the glass fiber 12' due to capillary action. Note that the temperature of the melt is slightly higher than the melting point (102° C.) of DMNPIIo in order to prevent decomposition of DMNPIIo. Thereafter, when the glass fiber 12' is rapidly cooled, the DMNPIIo that has entered the hollow portion becomes polycrystalline.

In addition, this glass fiber 12° was further added to DMNP.
DMNP11 in a molten state is gradually drawn out from the furnace maintained at a temperature higher than the melting point of II' (for example, 102°C 5°C) to the outside of the furnace maintained at a temperature lower than the melting point.
' is single-crystalized from the part drawn out of the furnace. As a result, an extremely long core 11 in a single crystal state with a uniform crystal orientation is formed, and the optical wavelength conversion element 10 can be made sufficiently long.

As is well known, the wavelength conversion efficiency of this type of optical wavelength conversion element is proportional to the length of the element, so the longer the optical wavelength conversion element is, the higher its practical value becomes.

Thereafter, both end faces of the glass fiber 12° are polished to a level of surface precision that allows optical contact. This surface precision is set to such a level that the maximum surface roughness is, for example, λ/10 (λ is the wavelength of incident light) or less.

Next, a 5FI (glass optical plane plate 13a) formed in a disk shape with approximately the same diameter as the glass fiber 12° is attached.
, 13b are brought into close contact with one end surface of the above-mentioned fibers in such a manner that foreign matter such as dust, moisture, air, etc., does not enter between them. Then, the optical plane plates 13a and 13b are joined to one end face of the fiber by means of a fan wire. In the manner described above, the fiber type optical wavelength conversion element 10 as shown in FIG. 1.2 is obtained.

The optical wavelength conversion element 10 is used as shown in FIG. That is, a laser beam (fundamental wave), which is a diverging beam, is emitted from a semiconductor laser (oscillation wavelength: 870 nm) 15 as a fundamental wave generating means, and is made into a parallel beam by a collimator lens 17, and further condensed by an objective lens 18. and converges into a small spot on the end face of the core 11 with the same diameter (1 μm in this example). Thereby, the laser beam 15 enters into the optical wavelength conversion element 10.

This fundamental wave 15 is converted into a second harmonic 15' whose wavelength is 1/2, that is, 435 nm, by the DMNP constituting the core 11.
is converted to This second harmonic 15° is the cladding 12
The light is emitted inside the element 10, undergoes repeated total reflection between the interface between its outer surface and the surrounding medium (usually air), and travels inside the element 10 toward the end face side. Phase matching is achieved between the waveguide mode of the fundamental wave 15 in the core part and the radiation mode of the second harmonic 15° to the cladding part (in the case of so-called Cerenkov radiation).

The output end face 10b of the optical wavelength conversion element 10 is connected to the second
A beam 15' containing harmonics 15' is emitted. This emitted beam 15'' is passed through a filter (not shown), and only the second harmonic wave 15' is extracted and used.

Here, in this optical wavelength conversion element 1o, the flat plates 13a and 13 as described above are provided on the element end faces 10a and 10b.
b is deposited on the core 11, so that the end face of the core 11 made of DMNP, which is an organic material, does not come into direct contact with an atmosphere such as air. Therefore, sublimation and metamorphosis of this core 11 are reliably prevented.

Further, since the flat plate 13aS13b is formed from the same material as the cladding 12, its coefficient of thermal expansion is naturally equal to that of the cladding 12. Therefore, even when the optical wavelength conversion element 10 undergoes a temperature change, the flat plate 13a, ISb
There is no possibility that a difference in thermal expansion or contraction will occur between the cladding I2 and the cladding I2, which will cause the flat plate 13a113b to easily peel off.

Note that the optical plane plates 13a and 13b are the cladding 12.
Although it may be formed from a material different from that of the cladding 12, it is particularly preferable to form it from the same material as the cladding 12 or a material having approximately the same coefficient of thermal expansion, since the above-mentioned effects can be obtained.

The embodiments in which the present invention is applied to a fiber type optical wavelength conversion element have been described above, but the present invention is also applicable to other types of optical wavelength conversion elements consisting of a cladding part and a waveguide part, that is, a two-dimensional optical waveguide type. It is also possible to apply the present invention to an optical wavelength conversion element or a three-dimensional optical waveguide type optical wavelength conversion element.

Furthermore, the present invention is applicable not only to an optical wavelength conversion element that converts a fundamental wave into a second harmonic, but also to an optical wavelength conversion element that converts a fundamental wave into a sum frequency, a difference frequency, or even a third harmonic. is also applicable. Furthermore, the present invention is applicable to optical waveguide devices other than optical wavelength conversion devices.

Furthermore, the optical waveguide device of the present invention is filled with an inert medium, as disclosed in Japanese Patent Application No. 63-230595 filed by the present applicant, in order to more reliably prevent sublimation and metamorphosis of the waveguide portion. It may be used by storing it in a sealed container.

(Effects of the Invention) As explained in detail above, in the optical waveguide device of the present invention, by attaching a flat plate to the element end face including the end face of the waveguide portion made of an organic material, the organic material on the end face of the waveguide portion is Sublimation or metamorphosis of the material is reliably prevented. Moreover, in the present invention, the plane plate can be formed by appropriately selecting a material with high barrier properties, and since the plane plate is fixed to the end face of the optical waveguide element by optical contact, it is possible to form the plane plate by appropriately selecting a material with high barrier properties. Therefore, deterioration of the waveguide section can be more reliably prevented.

Therefore, according to the present invention, the effective length of the optical waveguide element can be kept long, and the light incidence efficiency into the optical waveguide and the light output efficiency from the optical waveguide can be kept high.

Therefore, when the present invention is applied particularly to an optical wavelength conversion element,
High wavelength conversion efficiency can be achieved by maintaining high input coupling efficiency of the fundamental wave to the waveguide and furthermore, high output efficiency of the wavelength-converted wave from the waveguide.

[Brief explanation of drawings]

1 and 2 are respectively a perspective view and a schematic side view showing an optical wavelength conversion device which is an embodiment of the optical waveguide device of the present invention, and FIG. 3 illustrates a method for manufacturing the optical wavelength conversion device. FIG. 10... Optical wavelength conversion element 10a, 10b...
Element end face 11... Core 12... Clad 13a, 13b... Optical flat plate

Claims (1)

[Claims] In an optical waveguide element including a waveguide made of an organic material, a transparent optical plane plate is attached to the end face of the element including the end face of the waveguide with an optical contact. An optical waveguide element characterized in that a waveguide end face and the surrounding atmosphere are isolated by a flat plate.