JPH07140502A - Optical wavelength conversion element and optical wavelength conversion module formed by using the same - Google Patents

Abstract

PURPOSE:To provide the optical wavelength conversion element which has high wavelength conversion efficiency and is capable of efficiently generating second harmonic waves of a blue region and the optical wavelength conversion module formed by using this element. CONSTITUTION:This optical wavelength conversion element 1 consists of a single crystal of a compd. expressed by the formula and is provided with a core 11 arranged with a Z-axis of the induction main axes thereof in parallel with the core axis. This optical wavelength conversion module A consists of the optical wavelength conversion element 1 which is formed by combining a semiconductor laser beam source 3 which generates a laser beam of a wavelength of 0.80 to 1.00mum and a condensing optical system 2 which condenses the laser beam by polarizing the laser beam toward the X-axis or Y-axis of the induction main axes of the single crystal of the core 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength conversion element for converting the wavelength of laser light by utilizing a second-order nonlinear optical effect, and an optical wavelength conversion module using this optical wavelength conversion element. .

[0002]

2. Description of the Related Art Conventionally, attempts have been made to convert the wavelength of laser light (shorten the wavelength) by utilizing the second-order nonlinear optical effect of a nonlinear optical material. As an optical wavelength conversion element for performing the above wavelength conversion, for example, "Basics of Optoelectronics" (A. Yariv, Kunio Tada, Takeshi Kamiya,
A bulk crystal type optical wavelength conversion element as shown on pages 200 to 204 of Maruzen Co., Ltd. is well known. Since birefringence is used, there is a problem that a material having no or very small birefringence even if the nonlinearity is large cannot be used, and the usable material is limited.

Therefore, as an optical wavelength conversion element for solving the above problems, a so-called optical fiber type has been proposed in which a core made of a single crystal of a nonlinear optical material is formed in a glass clad [! For example, "Organic Nonlinear Optical Materials" (written by Shinsuke Umegaki, published by Bunshin Publishing), No. 8
See pages 9-99]. In the optical fiber type optical wavelength conversion element, since it is easy to achieve phase matching between the fundamental wave and the second harmonic, the optical fiber type has recently been actively researched.

In order to improve the wavelength conversion efficiency of the optical fiber type optical wavelength conversion element, it is preferable to use a nonlinear optical material having a high nonlinear optical constant as the core.
Examples of the non-linear optical material having a high non-linear optical constant include 2-methyl-4-nitroaniline and N- (4 shown in pages 58 to 59 of the above-mentioned document "Organic Nonlinear Optical Materials".
-Nitrophenyl) -L-prolinol and N-
(4-Nitrophenyl) -N-methylaminoacetonitrile and the like are known.

[0005]

However, in any of the conventional non-linear optical materials as described above, the direction in which the maximum non-linear optical constant of each material can be used when forming an optical fiber type optical wavelength conversion element is considered. However, since the crystals are not oriented, there is a problem that the high wavelength conversion efficiency of the material itself is not sufficiently exhibited.

Further, in the optical wavelength conversion element of the optical fiber type, the longer the element is, the more the wavelength conversion efficiency is improved. However, all of the above-mentioned conventional nonlinear optical materials can obtain a uniform single crystal. There is also a problem that it is difficult and therefore unsuitable for producing a long device. Further, the light wavelength conversion element is expected to be used in an optical circuit using a semiconductor laser light source that generates a laser beam having a wavelength of about 0.80 to 1.00 μm. In each case, there is a problem that the light absorption in the blue region, which is the second harmonic of the laser light from the semiconductor laser light source, is large, and as a result, the generation efficiency of the second harmonic in the blue region is low.

The present invention has been made in view of the above circumstances, and has a high wavelength conversion efficiency, and particularly in the blue region.
An object of the present invention is to provide an optical wavelength conversion element capable of efficiently generating harmonics and an optical wavelength conversion module using the same.

[0008]

Means and Actions for Solving the Problems In order to solve the above problems, the optical wavelength conversion element of the present invention has the following formula (1):

[0009]

[Chemical 2]

3,5-dimethyl-1- (3-
It is characterized by comprising a core made of a single crystal of methyl-4-cyanophenyl) pyrazole, in which the Z axis of the dielectric main axis is arranged parallel to the core axis, and a clad made of glass. The optical wavelength conversion module of the present invention includes the optical wavelength conversion element of the present invention and a wavelength of 0.
A single transverse mode semiconductor laser light source for generating a laser light of 80 to 1.00 μm, and a laser light from this semiconductor laser light source in the X axis direction or the Y axis direction of the dielectric main axis of the single crystal of the core. A condensing optical system for condensing on the end face of the core of the light wavelength conversion element in a polarized state.

In the light wavelength conversion device of the present invention having the above-mentioned structure, the above formula (1) used as the material of the core is used.
The compound represented by the following (hereinafter referred to as “DMCP”) was previously disclosed by the present inventors in JP-A-4-348326 to exhibit a nonlinear optical effect, and a light having a wavelength of 0.34 μm or more including a blue region. However, in actually forming a fiber-type optical wavelength conversion element, how should the crystal orientation be set and which polarization direction of the fundamental wave should be incident? It was unclear whether high wavelength conversion efficiency could be obtained by setting such a direction.

Therefore, the inventors of the present invention have now made the above DMCP.
As a result of further studies toward the practical application of the optical fiber type optical wavelength conversion element using the
It was confirmed to have a crystal structure as shown in FIGS. 2 (a) to (c). 2 (a) is an a-axis projection view of the DMCP single crystal, FIG. 2 (b) is an ac plan view, and FIG. 2 (c) is a c-axis projection view. In these figures, only two molecules, which is the number of molecules in the unit cell, are shown.

From the above crystal structure, the present inventors have shown in FIG.
As shown in (b), the b-axis of the DMCP single crystal coincides with the Y-axis of its dielectric main axis, and the a-axis is tilted by 32.5 ° with respect to the X-axis of the dielectric main axis. It was confirmed that the angle of intersection with the axis was 90.30 °. It was also found that the single crystal of DMCP is a monoclinic system and its space group is Pa. Furthermore, the second-order nonlinear optical tensor d of the DMCP single crystal is

[0014]

[Equation 1]

It was also found that Where d
_12, the crystal axis a, as shown in FIG. 3 (b), b, determined with respect to the c principal dielectric axis X, Y, given the Z, light polarized in the Y-axis direction (hereinafter referred to as "Y-polarized light". Less Similarly, the light polarized in the X-axis direction is referred to as "X-polarized light" and the light polarized in the Z-axis direction is referred to as "Z-polarized light", and contributes to extracting the second harmonic of the X-polarized light. Is a nonlinear optical constant. Similarly, for d ₁₁ to d ₃₅ , incident light of polarized light shown in the column of incident light in Table 1 below is made to enter as a fundamental wave, and the second harmonic of polarized light shown in the column of second harmonic of the same table is taken out. It is a non-linear optical constant that contributes to the case. In addition, the measured value (p
m / V) is the result of obtaining the actual value of each of the above-mentioned nonlinear optical constants by X-ray structural analysis.

[0016]

[Table 1]

From Table 1 above, the nonlinear optical constants d ₁₁ and d ₁₂
It can be seen that and d ₂₆ have large values. Of these, in order to use the nonlinear optical constant d ₂₆ , it is necessary to make X-polarized and Y-polarized fundamental waves incident.
However, due to its refractive index anisotropy, the fundamental wave cannot be converted into a single mode to generate the second harmonic with high efficiency.

On the other hand, in order to utilize the nonlinear optical constants d ₁₁ and d ₁₂ , as shown in FIG. 3 (a), a DMCP single crystal is made so that the Z axis of its dielectric main axis is parallel to the core axis. The core 11 is formed by orienting the core 11 so that the X-polarized or Y-polarized fundamental wave is incident on the end face of the core 11, whereby the second harmonic can be efficiently generated. Moreover, in the DCMP, as described above, it is easy to orient the Z axis in parallel with the core axis to form the long core 11 made of a uniform single crystal.

Therefore, the optical wavelength conversion device of the present invention in which a DMCP single crystal is oriented so that the Z axis of its dielectric main axis is parallel to the core axis, forms a core, and the DMCP itself has a high wavelength conversion efficiency. Is sufficiently exhibited, the wavelength conversion efficiency is high, and the second harmonic can be efficiently generated. Further, by converting the fundamental wave incident on the optical wavelength conversion element of the present invention into a single mode,
It is also possible to further improve the generation efficiency of the second harmonic.

As described above, the DMCP has a wavelength of 0.34 μm or more including the blue region, particularly 0.45.
Since it does not absorb light of around μm, the second harmonic in the blue region can be efficiently generated, and the wavelength is 0.80 to 0.80.
It can be used for an optical circuit using a semiconductor laser light source that emits a laser beam of around 1.00 μm. The optical wavelength conversion module of the present invention, the optical wavelength conversion element,
A single transverse mode semiconductor laser light source for generating a laser light having a wavelength of 0.80 to 1.00 μm as a fundamental wave, and a laser light from this semiconductor laser light source among the dielectric main axes of the single crystal of the core. The second harmonic of the blue region from the light wavelength conversion element is provided since it has a condensing optical system for condensing on the end face of the core of the light wavelength conversion element in a state of being polarized in the X-axis direction or the Y-axis direction. Waves can be generated efficiently.

[0021]

The present invention will be described in more detail based on the following examples. FIG. 1 is an explanatory diagram showing an optical wavelength conversion module A according to the present invention. This optical wavelength conversion module A
Is an optical wavelength conversion element 1 of optical fiber type, a condensing optical system 2
And a laser light source 3.

The fiber type optical wavelength conversion element 1 is a DM
The DMCP single crystal has a core 11 made of a CP single crystal and a clad 12 made of glass. As described above, the DMCP single crystal has a dielectric property in order to sufficiently exhibit the high wavelength conversion efficiency of the DMCP itself. The Z axis of the main axes is formed so as to be arranged in parallel with the core axis. Focusing optics 2
Is a collimator lens 21, anamorphic prism pairs 22, 23, a λ / 2 plate 24, and a condenser lens 25 in order from the laser light source 3 side to the light wavelength conversion element 1 side.
It is configured by arranging.

Further, as the laser light source 3, a single transverse mode semiconductor laser light source for generating a laser beam having a wavelength of 0.80 to 1.00 μm as a fundamental wave is used. According to this optical wavelength conversion module A, the wavelengths of 0.80 to 1.
The laser beam 31 a of 00 μm is made into a parallel beam by the collimator lens 21. Next, the light passes through the anamorphic prism pairs 22 and 23 and the λ / 2 plate 24, is condensed by the condenser lens 25, and is then irradiated onto the incident end surface 11 a of the core 11 of the light wavelength conversion element 1.

At this time, when the λ / 2 plate 24 of the condensing optical system 2 is rotated, the polarization of the laser light 31a irradiated on the incident end face 11a of the core 11 is changed to the dielectric of DMCP single crystal forming the core 11. Of the main axes, it may be the X-axis or Y-axis direction. Therefore, the laser light 31a that is condensed and polarized in the X-axis or Y-axis direction is applied to the incident end face 11a of the core 11 made of the DMCP single crystal. Using the large non-linear optical constant of the single crystal of, the laser light 31a, which is the fundamental wave, is converted into the second harmonic having a wavelength in the blue region with high conversion efficiency, and the second harmonic 31b is converted into
It can be generated in a ring shape from the emission end face 12b of the cladding 12 of the fiber-type wavelength conversion element 1.

The light wavelength conversion element 1 can be manufactured by various methods. For example, as shown in FIG. 4, sublimated and purified DMCP powder d1 is packed in a sharp-pointed ampoule tube 5, and a glass capillary tube serving as the clad 12 of the optical wavelength conversion element 1 is put therein. Next, after the inside of the ampoule tube 5 is evacuated and sealed, the ampoule tube 5 is
Is placed in a furnace 4 heated to a temperature slightly higher than the melting point of DMCP, 105 ° C. (for example, 110 ° C.).

Then, DMCP is melted and its melt d2
Are filled in the clad 12 by a capillary phenomenon.
Then, as shown by the arrow in the figure, connect the ampoule tube 5 to the D
When gradually pulled out of the furnace kept at a temperature lower than the melting point of MCP, a single crystal of DMCP grows in the cladding 12 to form the core 11. At this time, as shown in the figure, if the DMCP powder d1 at the tip of the ampoule tube 5 is not melted, this DMCP powder d1 becomes a seed crystal, and a DMCP single crystal is surely formed in the clad 12. Can be grown to.

Then, the optical wavelength conversion element is obtained by cutting the portion of the clad 12 in which the core 11 made of DMCP single crystal is formed with a fiber cutter or the like. According to the above method, in the glass capillary clad 12,
Core 1 with a length of 50 mm or more made of DMCP single crystal
Since 1 can be formed, an optical wavelength conversion element having a sufficient length can be obtained. Further, the crystal orientation of the single crystal of the core 11 formed by the above method is as shown in FIG.
As shown in (a), the Z axis of the dielectric main axis extends in parallel with the core axis, so the manufactured optical wavelength conversion element 1 sufficiently exhibits the high wavelength conversion efficiency of DMCP itself. Therefore, the wavelength conversion efficiency is high, and the second harmonic can be efficiently generated.

The glass capillary used in the above method is made of lead glass having a high refractive index such as SF15 and having an outer diameter of about 1 mm and an inner diameter of about 3 μm. Further, it is preferable to use a Bridgman furnace as shown in FIG. 4 for crystal growth of DMCP. The speed of drawing the fiber out of the furnace is preferably about 3 mm / hour in order to obtain a good DMCP single crystal.

Optical wavelength conversion element 1 formed by the above method
1 was used to assemble an optical wavelength conversion module A having the structure shown in FIG. 1, and a laser light source 3 emitted a semiconductor laser having a wavelength of 0.98 μm as a fundamental wave. When the incident end face 11a of the core 11 of the light wavelength conversion element 1 was irradiated with the condensed semiconductor laser which was polarized in the Y-axis direction by the above-mentioned method, the wavelength of 0. It was confirmed that the second harmonic of 49 μm was generated.

The optical conversion element of the present invention is preferably used for the optical conversion module of the present invention, and for example, an optical pulse compression element [M. Yamashita et al., Applied Physics].
Letter, 58 (24), p2727, (1991)] and the like.

[0031]

As described above, according to the optical wavelength conversion element of the present invention, since the high nonlinear optical constant of DMCP can be utilized, the second harmonic can be obtained with high wavelength conversion efficiency. You can Further, since DMCP does not have a light absorption region at a wavelength of 0.34 μm or more, particularly around a wavelength of 0.45 μm, laser light having a wavelength of about 0.80 to 1.00 μm is used as a fundamental wave and the second harmonic of the blue region is used. The waves can be obtained efficiently.

Further, in the optical wavelength conversion module of the present invention, the optical wavelength conversion element has a wavelength of 0.80 to 0.80 as a fundamental wave.
A single transverse mode semiconductor laser light source for generating 1.00 μm laser light, and the laser light from this semiconductor laser light source is polarized in the X-axis direction or the Y-axis direction of the dielectric main axis of the single crystal of the core. In this state, the optical wavelength conversion element is provided with a condensing optical system for condensing on the end face of the core of the optical wavelength conversion element, so that the second harmonic in the blue region can be efficiently generated from the optical wavelength conversion element.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a light wavelength conversion module according to the present invention.

2 (a) to 2 (c) are diagrams for explaining the crystal structure of a DMCP single crystal that constitutes the core of the optical wavelength conversion device of the present invention.

FIG. 3 (a) is a diagram for explaining the crystal orientation of the DMCP single crystal that constitutes the core of the optical wavelength conversion device of the present invention, and FIG. 3 (b) is the crystal axis and the dielectric of the DMCP single crystal. It is a figure explaining the relationship with a main axis.

FIG. 4 is an explanatory diagram showing a step of the method of manufacturing the optical wavelength conversion element of the present invention.

[Explanation of symbols]

 A light wavelength conversion module 1 light wavelength conversion element 11 core 12 clad 2 condensing optical system 3 laser light source

Claims (2)

[Claims] 1. Formula (1): 3,5-dimethyl-1- (3-methyl-4-) represented by
A core made of a single crystal of (cyanophenyl) pyrazole, the Z axis of the dielectric main axis of which is arranged parallel to the core axis;
An optical wavelength conversion element comprising a clad made of glass. 2. A light wavelength conversion element according to claim 1, a single transverse mode semiconductor laser light source for generating a laser beam having a wavelength of 0.80 to 1.00 .mu.m as a fundamental wave, and this semiconductor. A condensing optical system for condensing the laser light from the laser light source on the end face of the core of the light wavelength conversion element in a state of being polarized in the X-axis direction or the Y-axis direction of the dielectric main axis of the single crystal of the core. An optical wavelength conversion module comprising.