JPH0682857A - Optical wavelength conversion element - Google Patents

Abstract

PURPOSE:To provide the optical wavelength conversion element having high conversion efficiency by using the single crystal of a specific cyclobutenedione deriv. CONSTITUTION:The single crystal of the cyclobutenedione deriv. expressed by formula is used. In the formula, * denotes an asymmetric carbon atom. The single crystal of the cyclobutenedione deriv. usually has 1 to 30mm<3> sizes. The d constant (d33) thereof has about 400pm/V value and has a high nonlinear optical constant. This single crystal is confirmed to be a triclinic crystal system and is the crystal in which the space groups are P1 and molecules line up in parallel according to an X-ray analysis. The angle phase matching of a type I and type II is possible with this single crystal by refractive indices and the assembling of the wavelength conversion element in a bulk state is possible when such single crystal is cut in the phase production direction. The use of the single crystal as a waveguide is possible as well and the wavelength conversion element exhibits high conversion efficiency for which d33 is sufficiently utilized.

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 device having a laser oscillating function and a function of converting a fundamental wave into a second harmonic having a half wavelength.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to convert laser light into a short wavelength. Specific examples of the light wavelength conversion element for performing such light wavelength conversion include, for example, “Basics of Optoelectronics” A. The one using a bulk crystal as shown in Yariv, Kunio Tada, Takeshi Kamiya (Maruzen Co., Ltd.), pp. 200-204 is well known. When using these crystals, a phase matching method that changes the angle using birefringence is used. However, the optical wavelength conversion element used in the phase matching method uses the birefringence of the crystal so that the phase matching condition is satisfied. There was a problem that I could not. As an optical wavelength conversion element capable of solving the above problems, for example, O. Sugiur
a, et al, Extended Abstrac
ts, Physical Concepts of
Materials for Novel Optoe
electronic Device Applicat
ions, SPIE, Vol. 1361, 59
9 (1990), a three-dimensional optical waveguide type optical wavelength conversion element is known. The second harmonic phase matching method using this three-dimensional optical waveguide is as follows: 1) phase matching between the fundamental wave mode and the second harmonic mode by film thickness control; and 2) the fundamental wave guided mode and the second wave mode. Two types of phase matching (Cherenkov radiation type phase matching) performed between the harmonics and the radiation mode of the substrate are well known. Of these two, 1) is promising because an output proportional to the square of the propagation length can be obtained.

Conventionally, potassium phosphate titanate (KTP = KTiOPO ₄ ) has been used as a crystal constituting an optical wavelength conversion element.
Inorganic nonlinear optical crystals such as lithium niobate (LN = LiNbO ₃ ) are known. By the way, the conversion efficiency is
Since the value becomes high in proportion to the square of the nonlinear optical constant of the material, the nonlinearity is larger than that of the inorganic nonlinear optical material,
In recent years, much research has been done on organic nonlinear optical materials having a fast response speed. Since an organic molecule has a polarization structure with one molecule, by growing a non-centrosymmetric crystal,
It can be used as a nonlinear optical crystal. The present inventors have already reported that the cyclobutenedione derivative molecule has a high non-linear effect by the powder method (Japanese Patent Laid-Open No. Hei 2).
-333172, 2-333173, 2-33
Nos. 3174 and 2-333175). In addition, as a result of X-ray analysis, the following chemical structural formula (I)

[0004]

[Chemical 2] It has been clarified that the cyclobutenedione crystal represented by the formula (* means an asymmetric carbon atom) is a triclinic system, a space group P1, and a molecule in which molecules are perfectly arranged one-dimensionally ( L.S. Pu, In “Materials for
Nonlinear Optics ": Chemica
S. I. Perspectives; Marder,
J. Sohn and G.M. Stacky Rd. ;
ACS Symposium Series No. Four
55; American Chemical Soc
iety: Washington DC, p331-
342 (1991), L.S. S. Pu, J .; Che
m. Comm. , 429 (1991)).

[0005]

The organic single crystal reported so far has a nonlinear optical constant (d constant) higher than that of the inorganic single crystal as described above, but it is 100 pm / V.
Single crystals having the above nonlinear optical constants are not well known. The cyclobutenedione derivative represented by the general formula (I) is also known to have a high nonlinear effect, but it is not yet known to be used as an optical wavelength conversion element. The present invention has been made under the above circumstances in the conventional art. That is, an object of the present invention is to provide a novel optical wavelength conversion element using a single crystal of cyclobutenedione derivative.

[0006]

Means for Solving the Problems As a result of investigations by the present inventors, a large-sized single crystal was obtained by growing crystals of a cyclobutenedione derivative under a specific condition using a polar solvent. This has led to the completion of the present invention. The light wavelength conversion element of the present invention is characterized by using a single crystal of the cyclobutenedione derivative represented by the structural formula (I).

The present invention will be described in detail below. The single crystal of the cyclobutenedione derivative used in the present invention is
The cyclobutenedione derivative represented by the above structural formula (I) is dissolved in a polar solvent, and within a range of an ambient temperature of 10 to 40 ° C., the temperature fluctuation range is kept within ± 1 ° C. and the amount is 0.1 to 1 minute. It can be produced by evaporating the solvent at an evaporation rate of 100 mm ³ . As the polar solvent, those that dissolve the cyclobutenedione derivative in the liquid temperature range of 10 to 40 ° C. can be used, and specifically,
Acetone, methanol, ethanol, etc. can be mentioned,
Methanol is particularly preferred. In the present invention, the crystal growth is performed especially at an ambient temperature of 10 to 25 ° C.
Keeping the temperature fluctuation range within ± 0.5 ° C, 3 in 1 minute
It is preferable to carry out at an evaporation rate of -10 mm ³ .

[0008]

The single crystal of the cyclobutenedione derivative produced as described above usually has a size of 1 to 30 mm ³ , and its d constant (d ₃₃ ) is about 400 pm.
It has a value of about / V and a high nonlinear optical constant. Further, according to X-ray analysis, it is confirmed that this single crystal is a triclinic system, a space group is P1, and molecules are arranged in parallel. This single crystal is capable of type I and type II angular phase matching due to the refractive index, and when this single crystal is cut in the phase matching direction, the optical wavelength conversion element can be assembled in a bulk state. Therefore, this single crystal can be used as a waveguide because it is a crystal in which the space group is P1 in the triclinic system and the molecules are arranged in parallel, and it can be used as an optical wavelength conversion element that sufficiently utilizes d _33. Shows high conversion efficiency.

[0009]

【Example】

Example 1 A cyclobutenedione derivative represented by the above formula (I) (D
Using a methanol solution of (AD), the evaporation rate of the solvent was set to a predetermined value in a room in which the temperature fluctuation range was kept within ± 0.1 ° C at 22 ° C, and seed crystals were grown in an Erlenmeyer flask. . As a result, when the evaporation rate was ^{3 to} 5 mm ³ / min, it was possible to obtain a crystal with a good shape of 0.5 to 1 mm square. Then, a saturated methanol solution of DAD was placed in an Erlenmeyer flask, and the Erlenmeyer flask was placed in an enclosure in which the temperature was kept constant. Then, the seed crystal obtained as described above was put into this Erlenmeyer flask, and at a temperature of 22 ° C.,
Keeping the temperature fluctuation range within ± 0.1 ° C, 3-5 mm ³ /
It was grown at an evaporation rate of min. As a result, up to 1x
A DAD crystal having a size of 4 × 4 mm ³ could be obtained. The supramolecular polarizability (β) of DAD measured by the solvatochromic method using dioxane is 171 × 10 7.
^Since it is ^-30 esu, the d constant of DAD is expected to be a considerably high value.

The single crystal thus obtained was subjected to Maker frin.
As a result of measuring the nonlinear optical constant d ₃₃ by the ge method, about 200
A high value of pm / V was obtained. In addition, a value close to 400 pm / V was obtained when the correction by scattering was added. When the phase matching curve was obtained from the refractive index, the results shown in FIG. 1 were obtained. This single crystal is adjusted to the phase matching angle as shown in FIG. 2 and the Nd ³⁺ : YAG laser (λ = 1064n
m) as the fundamental wave light source, the second harmonic (λ
= 532 nm) was obtained with high conversion efficiency. The result is shown in FIG. In FIG. 2, reference numeral 1 is a conion meter head that enables movement of the single crystal in the X, Y and Z directions and rotation of θ and ψ, on which the cyclobutenedione derivative single crystal 2 is mounted. Has been done. When this cyclobutenedione derivative single crystal 2 is rotated and the fundamental wave 3 is projected at a predetermined position (θ, ψ), it is extracted as the second harmonic wave 4. In this way, the light wavelength conversion element can be obtained.

FIG. 4 shows an application example of the present invention, showing a green laser excited by a semiconductor laser. Figure 4
In the figure, 5 is a semiconductor laser (SONY: SLD304V) having an oscillation wavelength of 810 nm, 6 is a collimating lens of f = 4.5 mm, 7 is a cylindrical lens of f = 80 mm, 8 is a focusing lens of f = 14.5 mm, and 9 Is highly reflective to the semiconductor laser 5 side with respect to light having a wavelength of 1060 nm and 530 nm, and has a wavelength of 81
A Nd: YVO ₄ crystal 10 coated with a coating (for example, a dielectric multilayer film) that is non-reflective with respect to 0 nm light is highly reflective for light with a wavelength of 1060 nm on the surface opposite to the semiconductor laser 5. In addition, the output mirror is provided with a coating that is non-reflective with respect to light having a wavelength of 530 nm.

The wavelength 81 emitted from the semiconductor laser 5
The monochromatic light (excitation light) of 0 nm is condensed by the optical system of the collimating lens 6, the cylindrical lens 7 and the focusing lens 8 and projected onto the Nd: YVO ₄ crystal 9. The Nd: YVO ₄ crystal 9 and the output mirror 10 form a cavity, and the excitation light projected from the Nd: YVO ₄ crystal 9 side generates a fundamental wave having a wavelength of 1060 nm in the cavity. The cyclobutenedione derivative single crystal 2 placed in the cavity and cut to the phase matching angle is
A second harmonic wave having a wavelength of 530 nm is generated. This second harmonic can be extracted from the output mirror 10 side.

As described above, according to the application example of the present invention, a green laser excited by a semiconductor laser can be provided. It should be noted that instead of the Nd: YVO ₄ crystal, Nd ³⁺ : YA
The same is true with a G crystal (however, the second harmonic is long 5
(32 nm) A green laser excited by a semiconductor laser can be provided.

[0014]

The optical wavelength conversion element using the cyclobutenedione derivative single crystal of the present invention exhibits a high conversion efficiency, and is used in, for example, an optical scanning recording device for performing precision scanning, an optical scanning reading device, and the like. You can

[Brief description of drawings]

FIG. 1 is a graph showing a phase matching curve of an optical wavelength conversion device of the present invention.

FIG. 2 is a diagram showing a state in which an optical wavelength conversion element of the present invention is placed.

FIG. 3 is a graph showing a tuning curve for phase matching by the optical wavelength conversion element of the present invention.

FIG. 4 is a schematic configuration diagram of a semiconductor laser-excited green laser device, showing an application example of the present invention.

[Explanation of symbols]

1 ... Conion meter head, 2 ... Optical wavelength conversion element, 3
... fundamental wave, 4 ... second harmonic, 5 ... semiconductor laser of 810 nm oscillation, 6 ... f = 4.5 mm collimating lens, 7 ... f = 80 mm cylindrical lens,
8 ... f = 14.5 mm focusing lens, 9 ... N
d: YVO ₄ crystal, 10 ... Output mirror.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keisuke Sasaki 5-4-9 Minamishinozaki-cho, Edogawa-ku, Tokyo

Claims (1)

[Claims] 1. The following structural formula (I): (In the formula, * means an asymmetric carbon atom.) A light wavelength conversion element characterized by using a single crystal of a cyclobutenedione derivative.