JPH05134281A - Production of nonlinear optical element - Google Patents

Abstract

PURPOSE:To easily produce the nonlinear optical element having periodic structures with a simple apparatus. CONSTITUTION:A substrate 11 constituted with gratings having the coherent length of an org. material having optical nonlinearity as a pitch and a flat planar substrate 12 are superposed on each other. These substrates are immersed in this state into a melt 13 of the org. material having the optical nonlinearity and is then pulled up to crystallize the org. material intruding into the spacing between the substrate 11 constituted with the gratings and the flat planar 12 substrate. The resulted nonlinear optical element can easily collimate beams in application, since the radiation pattern of the SHG light beam to be emitted is spotty. The element satisfies a phase matching conditions and generates the SHG light with the high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a nonlinear optical element capable of wavelength conversion with high efficiency, which is expected in the field of optical information processing.

[0002]

2. Description of the Related Art At present, a nonlinear optical element for wavelength conversion is being improved in efficiency by confining light energy in a minute region, and an element using a channel type waveguide and a fiber are used. Two shapes of the element utilizing the are believed to be influential.

In order to convert the wavelength with high efficiency, it is necessary to achieve phase matching. Several methods have been proposed for achieving phase matching, and a birefringent material can achieve phase matching by controlling temperature and the like. However, there are practical problems such as the need to precisely control the temperature and the incident angle of light. As other methods of phase matching, methods using Cherenkov radiation, quasi phase matching, and those having a periodic structure are being studied.

In particular, for wavelength conversion nonlinear optical elements, a single crystal core fiber or a flat plate waveguide element, which uses Cherenkov radiation, can be easily phase-matched, and its investigation has been advanced.

As a wavelength conversion element for a flat waveguide using Cherenkov radiation, an element using lithium niobate is under study, and a waveguide is produced by diffusing titanium on a substrate of lithium niobate. .. In the case of producing a waveguide using an organic low molecular weight material, two glass slides or the like to be the clad layer are stuck together, immersed in a melt or solution of an organic material, and then pulled up to lower the temperature. Alternatively, a slab type thin film waveguide is created by volatilizing the solvent.

As a fiber type wavelength conversion element utilizing Cherenkov radiation, an inorganic oxide single crystal fiber such as lithium niobate has been studied, and a laser pedestal method and a micro Czochralski method are used. Further, the organic low molecular weight material is produced by immersing the capillary tube in the melt or solution and then pulling it up, lowering the temperature or volatilizing the solvent.

[0007]

SUMMARY OF THE INVENTION SHG (Second Harmonic Ge) is utilized by utilizing Cherenkov radiation.
When the light is generated, the phase matching condition is loose, but the condition of the output beam is bad (the output beam is output in the conical direction), so consider an application device thereof. Above is a big obstacle.

In particular, an FFP (far field pattern) of Cherenkov radiation from an element using a flat waveguide (for example, Japanese Patent Laid-Open No. 63-279231) is
It has an arc shape, and even if a lens or the like is used, the beam cannot be narrowed down, and it is not suitable as a light source for an optical disk pickup, for example.

A fiber type element (for example, Japanese Unexamined Patent Publication No. 62-
231945), the FFP of the outgoing beam is ring-shaped, and it is possible to narrow the beam to the diffraction limit by using an axico lens or the like, but it is difficult to adjust the optical system.

Further, when manufacturing a single crystal core fiber, since it is necessary to manufacture a single crystal of an organic compound in a cylindrical tube, it is inevitable to manufacture an element that is homogeneous in the longitudinal direction of the fiber. Have difficulty.

On the other hand, studies to obtain quasi-phase matching have been carried out with lithium niobate crystals which are oxide derivatives. The principle of quasi-phase matching is 1962 by Armstrong et al.
It was proposed in 1980, but since the domain inversion technology on the order of micron is necessary, the study of making it into a device has not progressed. Although a single crystal fiber is produced by using the laser pedestal method, it is a very difficult technique to invert the domain into an arbitrary period.

In order to generate SHG light with high efficiency, phase matching is an essential condition, and another phase matching method capable of high efficiency conversion is expected. It is an object of the present invention to provide a method for manufacturing an element that is phase-matched and that can perform wavelength conversion with high efficiency.

[0013]

According to the present invention, a substrate in which a grating having a pitch of a coherence length of an organic material having optical nonlinearity is formed and a plate-shaped substrate are superposed on each other, A non-linear optical element characterized by immersing in a melt of an organic material having nonlinearity and then pulling up to crystallize the organic material that has entered between the substrate on which the grating is formed and the flat substrate. A manufacturing method is provided.

FIG. 1 is a diagram for explaining a method of manufacturing a nonlinear optical element according to the present invention. A substrate 11 on which a grating having a pitch of coherence length of an organic material having optical nonlinearity is formed and a flat substrate 12 are overlapped, and an organic material having optical nonlinearity represented by MNA or the like is used. Immerse in the melt 13. Then, the melt enters into the gap between the superposed substrates by a capillary phenomenon, and the gap between the superposed substrates is filled with the melt.

On the other hand, an appropriate temperature gradient is provided above the melt, and a substrate 11 having a grating having a pitch of the coherence length of an organic material having optical nonlinearity and a plate-shaped substrate are provided. By gradually pulling 12 from the melt 13 of the organic material having optical nonlinearity in a state of being superposed, the organic material entering the gap of the superposed substrates is crystallized from the cooled portion.

In this way, a nonlinear optical element having a periodic structure with the same pitch as the coherence length can be manufactured.

Further, the crystal direction of the device can be controlled and selected by a combination of the pulling direction and the direction in which the grating is cut.

[0018]

EXAMPLES MB as an organic material having optical nonlinearity
A-NP (2nitrobenzylamino, 5nitropyridine) was used. The maximum second-order nonlinear optical constant of MBA-NP is d ₂₂ , and the coherence length is about 2 μm.

MBA-NP melt (temperature: 82.5 ± 0.1 ° C.) in a state where a glass substrate having a grating with a pitch of 2 μm and a flat glass substrate are stacked.
It was dipped in. The glass substrate immersed in the MBA-NP melt above the melt having a temperature gradient of −0.5 deg / cm from the surface to the top is pulled up at a speed of 1 mm / hrs.
The thin film MBA-NP single crystal having a thickness of about 0.2 μm and a length in the pulling direction of about 10 mm was obtained.

As shown in FIG. 2, Nd:
YAG laser light (wavelength λ = 1.064 μm) 24,
The SHG light (wavelength λ = 0.532) is incident on the glass substrate 21 forming the grating and the non-linear organic material single crystal 23 between the flat glass substrates 22 and from the prism 27.
25 was taken out. In this way, about 90 nW of SHG light was obtained for 1 W of incident light.

[0021]

According to the manufacturing method of the present invention, a nonlinear optical element having a periodic structure can be easily manufactured with a simple apparatus. Further, the nonlinear optical element obtained by the manufacturing method of the present invention can easily collimate the beam because the emission pattern of the emitted SHG light beam is spot-like, and satisfies the phase matching condition to meet the SHG light. It can be generated with high efficiency.

[Brief description of drawings]

FIG. 1 is a drawing for explaining the manufacturing method of the nonlinear optical element of the present invention.

FIG. 2 is a configuration diagram of a wavelength conversion element.

[Explanation of symbols]

 11 Substrate Constituting Grating 12 Flat Plate Substrate 13 Melt of Organic Material Having Optical Nonlinearity 21 Substrate Comprising Grating 22 Flat Plate Substrate 23 Single Crystal of Organic Material Having Optical Nonlinearity 24 Laser light 25 SHG light 26 Prism 27 Prism

Claims (1)

[Claims] 1. A melt of an organic material having optical non-linearity in a state in which a substrate having a grating having a pitch of coherence length of the organic material having optical non-linearity and a flat substrate are superposed on each other. A method for manufacturing a non-linear optical element, which comprises immersing the substrate in the substrate and then pulling it up to crystallize the organic material that has entered between the substrate on which the grating is formed and the plate-shaped substrate.