JPH02167531A - Light wavelength converting device - Google Patents

Abstract

PURPOSE:To prevent an organic nonlinear optical material from being sublimated or denatured and to hold the wavelength conversion efficiency of a light wavelength converting element high by confining the light wavelength converting element which performs wavelength conversion by the organic nonlinear optical material in an inactive medium. CONSTITUTION:The light wavelength converting element 10, a semiconductor laser 16 which generates a fundamental wave 15 to be wavelength-converted by the converting element 10, and a collimator lens 17 and an objective 18 as an incidence optical system which enters the fundamental wave 15 into the core 11 of the light wavelength converting element 10 are stored in a sealed container 20, and fluorine-based oil 21 is charged as the inactive medium. The light wavelength converting element 10 is an optical fiber formed by charging the core 11 made of a nonlinear optical material in the hollow part in the center of the clad 12. Consequently, the end surface of the core 11 made of PRA as an organic material never contacts an atmosphere such as air and the core 11 is prevented from being sublimated or denatured. Further, the wavelength conversion efficiency of the light wavelength converting element is prevented from decreasing and the handling performance is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical wavelength conversion device that converts a fundamental wave into a second harmonic, a sum frequency, a difference frequency, etc. This invention relates to an optical wavelength conversion device that performs wavelength conversion using an optical wavelength conversion element using.

(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. Specifically, as an optical wavelength conversion element that performs wavelength conversion in this way, for example, there is a bulk optical device as shown in "Fundamentals of Optoelectronics JA," written by YARIV, translated by Kunio Tada and Takeshi Kamiya (Maruzen Co., Ltd.), pages 200-204. Crystal type devices are well known. However, since this optical wavelength conversion element uses the birefringence of the crystal to satisfy the phase matching condition, it is possible to use materials with no or small birefringence even if the nonlinearity is large. The problem was that it was not available.

As an optical wavelength conversion element that can solve the above problems,
A so-called fiber type has been proposed. This optical wavelength conversion element is an optical fiber whose cladding is filled with a core made of nonlinear optical feed, and is published in Journal of the Micro-Optics Research Group of the Japan Society of Applied Physics Vol. 3.
An example is shown in No. 2+ p28-32. Since this fiber-type optical wavelength conversion element can easily achieve phase matching between the fundamental wave and the wavelength-converted wave, research on this fiber-type optical wavelength conversion element has been actively conducted recently. Furthermore, as shown in, for example, Japanese Unexamined Patent Publication No. 63-15233 and No. 63-15234 by the present applicant, a slab-shaped leading waveguide made of a nonlinear optical material is formed between two substrates serving as a cladding layer. , two-dimensional optical waveguide type optical wavelength conversion elements are also known.

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 single substrate serving as a cladding layer. This guided waveguide type optical wavelength conversion element also has the above-mentioned features.

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

Since this organic nonlinear optical material has an extremely large nonlinear optical constant compared to inorganic materials, it is possible to obtain high wavelength conversion efficiency by using this organic nonlinear optical material. Examples of this organic nonlinear optical material include Japanese Patent Application Laid-Open No. 60-250334 and “Nonliner 0
physical properties of O
rganjc and PoiymerjcMat
erjals” A CS S YMP OS I
UM 5ERIES 223. David J.
Edited by Williams (American Chemi)
Cal 5ociety, 1983) "Organic Nonlinear Optical Materials" Masao Kato 1 Supervised by Yabe Nakanishi (C.M.
(published by Cisha, 1985), “Non1inear O
physical properties of O
rganfcMolecules and Crys
tals” D, S, Chemla and J.
, edited by Zyss (Academic Press I
nc.

1987), “The Quality and Perror” by R.T., Balley et al.
rnance of TheOrganic Non
-Linear 0ptical Material
()2-Ca-Methylbenzyla
llino) -5-Njtropyridine
(M B A -NP)” (○plies C
omnications, Vol. 65.
No. 3, P229), etc.
(2-methyl-4-nitroaniline), mNA (methanitroaniline), POM (3-methyl-4-nitropyridine-1-oxide), urea, NPP [N-(
4-nitrophenyl)-(S)-prolinol], N
PAN (2[N-(4-nitrophenyl)-N-methylaminocoacetonitrile), DAN (2-dimethylamino-5-nitroacetanilide), MBA-N
P [2-N (α-methylbenzylamino)-5nitropyridine] Furthermore, JP-A-62-21 by the present applicant
3,5-dimethyl-1-(4
-nitrophenyl)pyrazole, 3,5-dimethyl-1
-(4-nitrophenyl)1.2.4-1 lyazole,
2-ethyl-1(4-nitrophenyl)imidazole,
Examples include 1-(4nitrophenyl)pyrrole, 2-dimethylamino 1-5-nitroacetanilide, 5-nitro-2-pyrrolidinoacetanilide, 3-methyl-4nitropyridine-N-oxide, and the like.

For example, MNA is LiNbO, which is an inorganic nonlinear optical material.
Since it has a wavelength conversion efficiency about 2000 times higher than that of 3, if an optical wavelength conversion element is formed using this organic nonlinear optical material, it is possible to convert infrared laser light from a small and low-cost semiconductor laser inside the shell. By generating a second harmonic or the like as the fundamental wave, it is also possible to obtain short wavelength laser light in the blue region.

(Problem to be Solved by the Invention) However, in the case of a fiber type or leading waveguide type optical wavelength conversion element obtained by configuring the core of an optical fiber or a leading wavepath 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 constituting 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 metamorphoses and ceases to be a single crystal. This results in the above-mentioned problem. In addition, in a three-dimensional optical waveguide type optical wavelength conversion element in which a guiding waveguide is embedded in the surface portion of a substrate, not only the end face but also the surface comes into contact with the surrounding atmosphere, so the above-mentioned problem occurs. more likely to occur.

Therefore, an object of the present invention is to provide an optical wavelength conversion device that can solve the above problems.

(Means and effects for solving the problem) The optical wavelength conversion device of the present invention includes a fiber type or guided waveguide type optical wavelength conversion element using the organic nonlinear optical material as described above, and a fundamental wave generating device. and an input optical system that makes the fundamental wave enter the organic nonlinear optical material of the optical wavelength conversion element.
The device is housed in an airtight container equipped with a transparent window that transmits the wavelength-converted wave emitted from the optical wavelength conversion element, and the airtight container is filled with an inert medium.

In the above configuration, the exposed portions of the organic nonlinear optical material, such as the end surfaces, come into contact with the inert medium, thereby preventing the above-mentioned sublimation and metamorphosis.

Even more preferably, the applicant's patent application No. 62-3
As disclosed in Japanese Patent No. 09145, a blocking layer is provided on the end surface of an organic nonlinear optical material to isolate this surface from an inert medium. Even if the organic nonlinear optical material is brought into contact with an inert medium as described above, the above-mentioned sublimation or metamorphosis may occur, although the progress is extremely slow compared to when it comes into contact with air or the like. However, if the above-mentioned blocking layer is provided, the end surfaces of the organic nonlinear optical material will not come into direct contact even with the inert medium, so that the above-mentioned sublimation or metamorphosis can be more reliably prevented. In addition, even if the barrier layer is made of organic resin, which has stability problems, the barrier layer is surrounded by an inert medium and deteriorates due to the atmosphere (for example, in the case of resin, it absorbs water vapor and deforms. You can prevent this from happening.

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

FIG. 1 shows an optical wavelength conversion device according to an embodiment of the present invention. This optical wavelength conversion device includes, in a sealed container 20, a fiber-type optical wavelength conversion element 10, a semiconductor laser 1B that emits a fundamental wave 15 whose wavelength is converted by this optical wavelength conversion element IO, and A collimator lens (7) and an objective lens 18 are housed as an incident optical system for inputting light into the core 11 of the wavelength conversion element 10, and the sealed container 20 is filled with fluorine-based oil 21, which is an inert medium. Note that the optical wavelength conversion element (0 is held by the holding member 22, and the lens 1
7.18 is held by the lens barrel 23 and the holding member 24,
Further, the semiconductor lasers 16 are held by holding members 25 and fixed inside the closed containers 20, respectively. Further, the power source 26 of the semiconductor laser 1G is led out of the container from the opening 20a of the closed container 20 via a current introduction terminal 27 such as a hermetic seal. The current introduction terminal 27 has an opening 20
a to keep the inside and outside of the closed container 20 watertight.

Next, the optical wavelength conversion element IO will be explained in detail.

As clearly shown in FIG. 2, 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, the core 11 is formed of 3,5-dimethyl-1-(4-nitrophenyl)pyrazole (hereinafter referred to as PRA), which is disclosed in Japanese Unexamined Patent Publication No. 62-210432 by the applicant of the present application.

Here, as an example, a method for manufacturing the optical wavelength conversion element IO will be described in the case where the core 11 is formed from the above-mentioned PRA and the cladding 12 is formed from 5FS3 glass. First, a hollow glass fiber 12' which will become the cladding 12 is prepared. As an example, the glass fiber 12' has an outer diameter of 3 mm and a hollow portion diameter of 2 μm. Then, as shown in Fig. 3, P RA 11'
is kept in a molten state, and glass fibers 12 are placed in this melt.
° Infiltrate one end. Then, due to capillarity, the PRA 11' in a molten state enters the hollow portion of the glass fiber 12'. Note that the temperature of the melt is PRAII
To prevent decomposition of ', the temperature is slightly higher than its melting point (102°C). Then glass fiber 12
When the PRA 11 was rapidly cooled, the PRA 11 that had entered the hollow part
' becomes polycrystalline.

Next, this glass fiber 12'' is melted by gradually drawing it out of the furnace maintained at a temperature higher than the melting point of PRA 11'' (for example, 102.5°C) to the outside of the furnace maintained at a temperature lower than the melting point. The PRA 11' in this state is single-crystalized from the part drawn out of the furnace. As a result, the core 11 is in an extremely long single crystal state and has 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.

After the core (1) is filled as described above, an acrylic resin such as an acrylic-styrene copolymer is applied to both end surfaces of the glass fiber 12', which has been cut at both ends as appropriate, to form a blocking layer 13a. 13b is formed.The formation of the blocking layers 13a and L3b is carried out by, for example, preparing a coating acid in which acrylic resin is diluted with water, dipping both ends of the fiber in this solution, and then drying. As a result, an optical wavelength conversion element 1o as shown in Figs. 1 and 2 is obtained.The blocking layers 13a and L3b are formed to have a thickness of, for example, about 1 μm.

The above-mentioned optical wavelength conversion element (0 is used as shown in FIG. The beam is made into a parallel beam, further condensed by the objective lens 18, and then passed through the blocking layer 13a to the element end face l.

irradiated onto a. This laser beam 15 converges on a small spot on the end face of the core (t) with the same diameter (2 μm in this example) as the core.Thereby, the laser beam 15 enters the core 11. This fundamental wave 15 is The second harmonic 15' with a wavelength of 172 is generated by the PRA 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 its outer surfaces, and travels inside the element 10 toward the end face side. Phase matching is achieved between the guided mode of the fundamental wave 15 in the core and the radiation mode of the second harmonic 15' to the cladding (in the case of so-called Cerenkov radiation).

From the output end face 10b of the optical wavelength conversion cable 10, the second
A beam 15'' containing harmonics 15'' is emitted.
8, and passes through a filter (not shown), where only the second harmonic 15' is taken out and used. The filter and a lens for collimating and condensing the second harmonic wave 15' may be provided in the closed container 20, and the condensed second harmonic wave 15' may be emitted through the transparent window 28.

In this device, the optical wavelength conversion element 10 is confined within the fluorine-based oil 2 (inert medium), so that the end surface of the core 11 made of PRA, an organic material, does not come into contact with the atmosphere such as air. Therefore, sublimation and metamorphosis of the core 11 are prevented.Moreover, in this embodiment, since the blocking layers 13a and 13b are provided on both end faces of the optical wavelength conversion element 10, the end faces of the core 11 are protected from the fluorine-based oil 2 ( Therefore, the above-mentioned sublimation and metamorphosis can be more reliably prevented.

Note that if the blocking layers 13a and 13b are provided, the preferable results as described above can be obtained, but they do not necessarily need to be provided in such an iQI cutoff.

Furthermore, in the above embodiment, the fluorine-based oil 21 is used as the inert medium filled in the closed container 2o.
Other examples of this inert medium include silicone oil and liquid paraffin for liquids, N Z and He for gases.
s N e % A r SK r s X e % etc. can be used. Furthermore, in the above embodiment, acrylic resin is used as the material for the barrier layers 13a and 13b, but the material for the barrier layers 13a and 13b is as follows:
In addition, silicone resins, epoxy resins, fluororesins, gelatin, casein, cellulose, polyvinyl alcohol, and the like can be used.

Further, in the above embodiment, a fiber type optical wavelength conversion element 10 is used, but the optical wavelength conversion device of the present invention may be constructed using the above-mentioned two-dimensional or three-dimensional optical waveguide type optical wavelength conversion element. Of course, it is also possible.

Further, although the above embodiment converts the fundamental wave into a second harmonic, the optical wavelength conversion device of the present invention may also use an optical wavelength conversion element that converts the fundamental wave into a sum frequency, a difference frequency, etc. It can also be configured as follows.

(Effects of the Invention) As explained in detail above, the optical wavelength conversion device of the present invention has a configuration in which the optical wavelength conversion element that performs wavelength conversion using an organic nonlinear optical material is confined in an inert medium. Sublimation or metamorphosis of the material is reliably prevented. Therefore, according to this optical wavelength conversion device, it is possible to prevent the incident coupling efficiency of the fundamental wave from decreasing and maintain a high wavelength conversion efficiency of the optical wavelength conversion element. Furthermore, the above configuration prevents dust from adhering to the end face of the optical wavelength conversion element, the semiconductor laser, the lens, etc.
Alternatively, it is possible to prevent scratches, and from this point, it is possible to prevent the wavelength conversion efficiency of the optical wavelength conversion element from decreasing, and furthermore, it is possible to obtain the effect of improving the ease of handling.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view showing an optical wavelength conversion device according to an embodiment of the present invention, FIG. 2 is a perspective view showing an optical wavelength conversion element used in the device of the above embodiment, and FIG. FIG. 2 is a schematic diagram illustrating a wide range of manufacturing methods of the optical wavelength conversion element.

Claims (1)

[Claims] An optical wavelength conversion element comprising an organic nonlinear optical material covered with a cladding layer having a lower refractive index than the cladding layer, which converts the wavelength of an incident fundamental wave and emits it, and generates the fundamental wave. a light source; an input optical system that makes the fundamental wave enter the organic nonlinear optical material of the optical wavelength conversion element; and an input optical system that houses the optical wavelength conversion element, the light source, and the input optical system, and that converts the wavelength emitted from the optical wavelength conversion element. An optical wavelength conversion device consisting of an airtight container equipped with a transparent window that transmits converted waves, and an inert medium filled in the airtight container.