JPH0266527A - Wavelength conversion element - Google Patents

Abstract

PURPOSE:To eliminate defects such as exfoliation and cracks of a single crystal and to improve conversion efficiency by using a high-polymer compd. having a specific modulus of elasticity as a member to come into contact with a material having optical nonlinearity. CONSTITUTION:The org. material having the optical nonlinearity is exemplified by arom. rings such as benzene and naphthalene substd. with an electron- attracting group and electron-donating group, stilbene, etc., as represented by, for example, nitroaniline deriv. The thin film 2 of the single crystal of the org. nonlinear optical material is formed on, for example, a polypropylene substrate 1. Various high-polymer compds. having the modulus of elasticity in a 0.3X10<4> to 4.0X10<4>kg/cm<2> range are used as the high-polymer compd. The dealing with the defects such as distortions, cracks and exfoliation generated by a difference in the coefft. of thermal expansion between the substrate 1 and the org. nonlinear optical material is enabled in this way and the production is facilitated; in addition, the conversion efficiency is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a wavelength conversion element used in an optical harmonic generator or the like used for wavelength conversion of laser light.

[Background of the Invention] Since the discovery of nonlinear optical effects in 1961, research has been conducted on materials having nonlinear optical effects and devices that utilize nonlinear optical effects. Conventionally, materials with nonlinear optical effects include LiNbO5 and KDP.
Inorganic materials such as (KH2PO4) were known.

However, in recent years, organic materials, which have significantly higher nonlinear optical constants than these inorganic materials, have begun to attract attention.

Such substances include, for example, MNA (2-methyl-4-nitroaniline), mNA (metanitroaniline), RO
M (3-methyl-4-nitropyridine-1-oxide) and the like.

As devices using these organic nonlinear optical materials, devices in which a single crystal thin film of a nonlinear optical material is formed on a glass substrate are known.

However, in manufacturing the above device, the temperature must be raised above the melting point of the organic nonlinear optical material, so that the thermal expansion of the substrate Il! Due to the difference between the coefficient and the coefficient of thermal expansion of the organic nonlinear optical material, a single crystal could not be formed properly, and in the worst case, the single crystal could peel off from the substrate. Furthermore, when the present inventors attempted to solve the problem, single crystal peeling, cracking, etc. occurred significantly in organic nonlinear optical materials with excellent single crystallinity.

In addition, due to the long-term exposure to high temperatures, impurities from the glass substrate were diffused into the crystal, resulting in a decrease in conversion efficiency.

A second harmonic generation element using an epoxy resin capillary tube is known. (J, Opt, Soc, An+, B
Vol.4. No. 6 (June 1987) p.
998-1012) The present inventors investigated the second harmonic generation element and found that although the generation of defects due to impurity diffusion could be prevented in the element, peeling of the single crystal, Defects such as cracks occur, making it difficult to obtain a second harmonic generating element with good conversion efficiency.

Furthermore, in a conventionally known second harmonic generation element in which an organic nonlinear optical material is formed on a substrate or in a hole provided on the substrate, an epoxy resin was used as the substrate, but the above-mentioned defects were not solved. There wasn't.

Therefore, the present inventors investigated and found that by using a polymer compound with a specific elastic modulus (rigidity) as a member in contact with a substance having optical nonlinearity, peeling, cracking, etc. of the single crystal can be prevented. It has been found that a second harmonic generation element with good conversion efficiency can be obtained without any drawbacks.

[Object of the Invention] Therefore, the object of the present invention is to deal with defects such as defects that occur in organic nonlinear optical materials due to impurity diffusion from the substrate, and defects such as distortion, cracks, and peeling that occur due to the difference in coefficient of thermal expansion between the substrate and the organic nonlinear optical material. Another object of the present invention is to provide a wavelength conversion element that is easy to manufacture and has high conversion efficiency.

[Structure of the Invention] The above object is to form a material made of a material having optical nonlinearity and a member adjusted so that the waveguide mode of the fundamental wave and the waveguide mode or radiation mode of the second harmonic are phase matched. In the wavelength conversion element, the substance is an organic substance, the member is in contact with the substance, and the elastic modulus (
rigidity) is 0.3 xlQ'kr/-~4. Ox10
This was achieved using a wavelength conversion element characterized by being a polymer compound with a high molecular weight of 1 kg/cd.

Next, the present invention will be explained in detail.

Regarding substances with optical nonlinearity, for example, "Organic Nonlinear Optical Materials" (published by CMC Co., Ltd. in 1985), rNonlinear 0ptical P
properties of Organic Mo1ec
ules and CrystalJVol, 1.

2 (Acadenic Presslnc, 1
987), and is described in the annual meeting proceedings of the Chemical Society of Japan from 1954 to 1956.

Examples of substances having optical nonlinearity that are preferably used in the present invention include aromatic rings such as benzene and naphthalene substituted with electron-withdrawing groups and electron-donating groups represented by nitroaniline derivatives, and heterogeneous rings such as pyridine and pyrimidine. Mention may be made of ring, stilbene, pyridine-N-oxide and urea.

Preferred examples of organic substances having optical nonlinearity used in the present invention are shown below.

Margins Below In the above, compounds with Nα of 10 to 16 are preferred, and compounds with Nα of 10.11.12.16 are more preferred in consideration of single crystallinity and nonlinear optical effects.

The polymer compound of the present invention has an elastic modulus (rigidity modulus) of 0.
．． 3 x 10' kg/-~4.0 x 10' k
+r/Cl11 (Measurement method ASTM: D747
) Various polymer compounds can be used as long as they have a modulus of elasticity (w1 modulus) of 0.3.
X 10' kg/cJ to 1.4 x 10' kr/- is preferable.

Further, the polymer material has a coefficient of thermal expansion of 1.0×10
-'~30x10-'/"C (measured by ASTM: D696) is preferable. Furthermore, the thermal expansion coefficient should be as close as possible to the organic nonlinear optical material used, with a difference of 0.4 xlO-'/" C) are preferred.

Next, the elastic modulus (rigidity modulus), heat resistance, refractive index, and thermal expansion coefficient of the preferable polymer compound used in the present invention will be shown.

High density polyethylene 120-135 Acrylonitrile-styrene copolymer 87-90 Polysulfone polycarbonate Polyvinylidene chloride 71-93 Polystyrene Vinyl chloride polypropylene 70-100 50-70 99-110 Test method for coefficient of thermal expansion 1.54 0.4-1 .1 2.8~3.5 1.63 2.4~2.7 1.59 2.0~2.4 1.60~1.63 0.3~0.6 1.59~1.60 2.8-4.2 1.52-1.55 2.5-4.2 1.48-1.50 0.9-1.4 ASTM D 696 1.0-1.1 6-8 4. 9-5.6 6-8 5-18.5 [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.Example 1 FIG. FIG. 2 is a diagram showing a nonlinear second harmonic generation element according to an embodiment of the present invention.

In FIG. 1, 1 is a polypropylene (modulus of elasticity (rigidity) 1.2 x 10' kr/d) substrate, and 2 is a nonlinear optical material, a single crystal thin film of vanillin.

FIG. 2 is a diagram for explaining a method of manufacturing the nonlinear second-order harmonic generating element of the present invention.

In FIG. 2, 3 represents a polypropylene substrate, and 4 represents an auxiliary substrate made of polyethylene.

A gap of 3 .mu.m is formed between the polypropylene substrate 3 and the auxiliary substrate 4 made of polyethylene by a spacer (3 .mu.m thick) 5.5' made of a polycarbonate film.

Add vanillin to the gap using the capillary method (Transactions of the Institute of Electronics and Communication Engineers '8)
8/10 VAT, J69-CNo, 10 p12
After filling the vanillin with 8fl+-1290), in order to make the vanillin thin film into a single crystal thin film, a vertical zone melting method was applied, and the inside of the furnace with temperature distribution was heated to 1111.
The mixture was lowered at a rate of 1/hour to allow recrystallization. Note that the temperature inside the furnace was 81°C.

After performing single crystallization in this manner, the auxiliary substrate 4 was separated, and a nonlinear second harmonic generation element was produced.

According to this example, defects such as cracks and peeling do not occur;
Furthermore, the single crystallinity was also better than that of a glass substrate. Furthermore, there was no distortion or contamination of impurities from the substrate, and the conversion efficiency was high.

Embodiment 2 FIG. 3 is a diagram showing a nonlinear second harmonic generation element according to another embodiment of the present invention.

In Figure 3, 6 is methyl methacrylate resin (PMM
A) C elastic modulus (wi elasticity modulus) 3.2 x10' kir
/-] substrate, and 7 indicates a single crystal thin film of var-bromoethoxy m:trobenzene (nonlinear optical material).

The above element is manufactured by forming a groove 8 having a depth of 3 μm and a width of 100 μm on a substrate 6 using a Guissing tool, and filling the groove 8 with powder of para-bromoethoxy m:trobenzene. It is heated to 66° C., which is the melting point of benzene, and crystals are formed in the grooves 8. The vertical zone melting method as in Example 1 was applied to the crystal to form a single crystal thin film 7. However, at this time, the temperature inside the furnace was 66° C., and the descent rate was 0.5 openings/h.

This example not only has the same effects as Example 1, but is also easier to manufacture, and since the substrate is also present on the side, the protection of the nonlinear optical material is increased.

Embodiment 3 FIG. 4 is a diagram showing a nonlinear second harmonic generation element according to another embodiment of the present invention.

In Figure 4, 9 is high-density polyethylene [elastic modulus (M
Bread) 0.7 x10' bread) Hollow 7y
10 represents a fiber-like single crystal of methyl para-hydroxybenzoate, which is a nonlinear optical material.

FIG. 5 is an explanatory diagram of the manufacturing apparatus for the nonlinear second-order harmonic generating element of the present invention.

In FIG. 5, reference numeral 11 denotes a melting furnace for melting the nonlinear optical material, and a hollow spit-like outlet 12 is provided at the bottom of the furnace. Heater 13 for melting methyl
is provided.

- The inner diameter of the outlet 14 of the outflow path 12 is 5 μm to 50 μm.
m is good.

15 is a melting furnace for melting high-density polyethylene, which is the material of the member adjusted so that the waveguide mode of the fundamental wave and the waveguide mode or radiation mode of the second harmonic are phase-matched; The lower part is tapered and serves as an outflow passage 16 for the member. Further, a heater 17 is provided around the lower part of the melting furnace 15. - Outflow channel 1 numerically
The inner diameter of the outlet 18 of No. 6 is preferably 1° to IQam.

A heater 19 with a temperature gradient is provided below the outlet passage 16.
is provided.

20 indicates the formed nonlinear second harmonic generating element.

When manufacturing a nonlinear second-order harmonic generation element using the above-mentioned manufacturing apparatus, a member is adjusted so that the nonlinear optical material, the waveguide mode of the fundamental wave, and the waveguide mode or radiation mode of the second-order harmonic are phase-matched. It is necessary that the melting points of the materials be approximately the same.

A nonlinear optical material, methyl rose-hydroxy-benzoate, is placed in the melting furnace 11, and a member is adjusted so that the waveguide mode of the fundamental wave and the waveguide mode or radiation mode of the second harmonic wave are phase-matched. The polyethylene material is put into a melting furnace 15, and each is heated to a temperature of 131°C to 140°C by a heater 13.
17 to melt.

When the melting furnace 11 and the melting furnace 15 are pressurized, fibrous polyethylene whose hollow part is filled with methyl vara-hydroxy-benzoate is obtained from the outlet 18 of the outlet 15.

By gradually lowering the temperature using one heater with a temperature gradient and single-crystallizing methyl para-hydroxybenzoate, the nonlinear second harmonic generating element 2 of the present invention is produced.
0 is obtained.

The device of this example not only has the same effects as Example 1, but also is easy to manufacture.

In addition, although the case where the nonlinear optical material was made into a single crystal was described in the said Example, the nonlinear optical material may be oriented.

[Effects of the Invention] As described above, according to the present invention, there is no cracking, peeling, etc., the single crystallinity is significantly improved, there is no strain, there is no contamination of impurities from the substrate, and there is a high conversion efficiency. It has become possible to form a harmonic generation element.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the wavelength conversion element of the present invention, FIG. 2 is a diagram for explaining a method of manufacturing the wavelength conversion element of FIG. 1, and FIG. 3 is a perspective view showing an embodiment of the wavelength conversion element of the present invention. FIG. 4 is a perspective view showing another embodiment of the wavelength conversion element of the present invention, and FIG. 5 is a perspective view of an apparatus for manufacturing the wavelength conversion element of FIG. 4. It is an explanatory diagram. Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] In the wavelength conversion element formed of a material having optical nonlinearity and a member adjusted so that the waveguide mode of the fundamental wave and the waveguide mode or radiation mode of the second harmonic are phase matched, The substance is an organic substance, the member is in contact with the substance, and the modulus of elasticity (modulus of rigidity) is 0.
．． 3 x 10^4 kg/cm^2 ~ 4.0 x 10^4 kg
A wavelength conversion element characterized in that it is a polymer compound with a wavelength of /cm^2.