JPH05100268A - Light wavelength converting element - Google Patents

Abstract

PURPOSE:To minimize the absorption of harmful light and prevent deterioration by providing a light shield layer on the external surface of a light wavelength converting element except in the light incidence area on a light incidence end surface and the light projection area on a light projection end surface. CONSTITUTION:The light wavelength converting element 4 is constituted into an optical fiber type and has a core 41 and a clad 42, and the light shield layer 43 is formed at the outer periphery of the clad 42 except the light incidence and projection end surfaces 44 and 45. In this case, when laser light is made incident on the core 41 of the light wavelength converting element 4, Cherenkov radiation based upon the laser light as a fundamental wave is caused and a generated secondary higher harmonic is projected and emitted while diffused in a ring shape. The projection converted light is collimated, further converged, and used for reading operation. At this time, the outer periphery is covered with the light shield layer 43, so light having wavelength which causes harmful optical deterioration is prevented from entering the core 41 or clad 42 from outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an optical fiber type having a structure in which a cylindrical optical waveguide (core) is surrounded by a clad, and a structure in which a clad is in contact with the upper surface, the lower surface or both surfaces of a planar optical waveguide. It is configured by a two-dimensional optical waveguide type, a three-dimensional optical waveguide type having a structure in which a clad is in contact with a three-dimensional optical waveguide portion (channel), or the like, and a fundamental wave that is laser light is incident on the optical waveguide portion, and its secondary The present invention relates to a light wavelength conversion element in which harmonics are emitted as converted light from an end face.

[0002]

2. Description of the Related Art The nonlinear optical effect is that light enters a medium.
Then, the polarization proportional to the higher-order term of the square of the electric field of the light
Is a phenomenon that occurs, and this phenomenon causes the second harmonic and sum
Waves, difference frequencies, etc. are generated. The material in which the above phenomenon appears is non-linear
Shaped optical material, KH₂PO_Four, LiNbO ₃Etc.
Inorganic materials are well known, but recently, 2-methyl
-4-nitroaniline (MNA), 4-dimethylamino
-3-acetamidonitrobenzene (DAN), 3,5
-Dimethyl-1- (4-nitrophenyl) pyrazole
Nonlinear optics with large organic materials represented by (DMNP)
It is attracting attention because it has a constant.

Recently, much research has been conducted to apply the above-mentioned organic nonlinear optical material to an optical wavelength conversion element that halves the wavelength of a low-power laser light source such as a semiconductor laser. It is important for the optical wavelength conversion element to be designed so that the fundamental wave is confined at a high energy density and the interaction length between the fundamental wave and the higher harmonic wave is lengthened.

Therefore, as the form of the optical wavelength conversion element, an optical fiber type or an optical waveguide type is used. In the optical wavelength conversion element of these forms, at least one of the optical waveguide section and the cladding having a lower refractive index than the optical waveguide section is composed of a single crystal or a polycrystal of an organic nonlinear optical material. High conversion efficiency is obtained by guiding the waves.

[0005]

However, the optical wavelength conversion element using the above-mentioned organic nonlinear optical material is disclosed by the incidence of light to the organic nonlinear optical material, particularly light having a wavelength in the light absorption region of the organic nonlinear optical material. Photolysis occurs. The graph of FIG. 5 shows the measured values of the light transmittance of a single crystal of DMNP and DAN, where DMNP has a wavelength of 0.45 μm or less, D
It can be seen that AN absorbs light having a wavelength of 0.48 μm or less. The reason why the transmittance of long wavelength light does not reach 100% is due to surface reflection.

Due to this light absorption, there is a problem that the light wavelength conversion element is deteriorated and the life of the light source device using the light wavelength conversion element is shortened. Therefore, an object of the present invention is to provide an optical wavelength conversion element that solves the above-mentioned technical problems and is less likely to cause deterioration of the optical wavelength conversion element due to irradiation of light, and that can prolong the life of the light source device. is there.

[0007]

According to a first aspect of the present invention, there is provided an optical wavelength conversion element, which includes at least a light incident area of a light incident end surface and a light emitting area of a light emitting end surface. Is provided with a light shielding layer on the outer surface thereof. The light-shielding layer does not need to be formed on the entire outer surface of the light wavelength conversion element except for the light incident area on the light incident end surface and the light emitting area on the light emitting end surface. The light emitting end face may not be formed at all.

[0008]

According to the above construction, since the light shielding layer is provided on the outer surface of the optical wavelength conversion element excluding the light input / output area, it is possible to apply the organic nonlinear optical material forming at least one of the optical waveguide portion and the clad. It is possible to minimize the incidence of harmful light.

[0009]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 2 is a conceptual diagram showing a basic configuration of a light source device using a light wavelength conversion element which is an embodiment of the present invention. This light source device collimates laser light generated from a laser light source 1 such as a semiconductor laser with a spherical lens 2,
The collimated light beam is condensed by the spherical lens 3,
The light is incident on the light wavelength conversion element 4.

The optical wavelength conversion element 4 is of an optical fiber type, as shown enlarged in FIG. 1, and has a core 41 and a clad 42, and
A light shielding layer 43 is formed on the outer periphery of the clad 42 except for the light incident / exiting end faces 44 and 45. The light-shielding layer 43 is composed of, for example, a light-reflecting film made of a metal such as aluminum or silver, a carbon film that does not transmit ultraviolet rays or visible light, a paint film, or the like. Any one or both of the core 41 and the clad 42 is formed by applying a known organic nonlinear optical material such as MNA and DAN.

When laser light is incident on the core 41 of the optical wavelength conversion element 4, Cherenkov radiation is generated with the incident laser light as a fundamental wave, and the generated second harmonic (converted light) is emitted and diffused in a ring shape. It is emitted while doing. The emitted converted light is collimated and further condensed to be used for reading an optical disk. In this case, since the outer periphery of the light wavelength conversion element 4 is covered with the light shielding layer 43, light having a wavelength that causes harmful light deterioration (for example, light having a wavelength of 0.5 μm or less in the case of DAN) is externally applied to the core 41 or the clad. Four
2 can be prevented. The fundamental wave and 2
Needless to say, since the second harmonic wave passes through the organic nonlinear optical material, problems such as deterioration due to light absorption do not occur.

FIG. 3 shows another embodiment of the light wavelength conversion element. In this example, the optical wavelength conversion element 5 is composed of a three-dimensional optical waveguide having a structure in which a channel 51 having a rectangular cross section is embedded in the upper surface of a clad 52. A light-shielding layer 53 is formed on the outer surface of the clad 52 and the upper exposed surface of the channel 51 except the light input / output end surfaces 54 and 55.

Also in this embodiment, when laser light is incident on the light incident end surface 54 of the channel 51, a second harmonic (converted light) is generated with the incident laser light as a fundamental wave, and the light emitting end surface 55 on the opposite side. Is emitted from. Then, it is possible to prevent light having a wavelength that causes optical deterioration due to the light shielding layer 53 from entering the channel 51 and the clad 52 from the outside.

Next, an example of manufacturing the light wavelength conversion element will be described. Here, a manufacturing example of the optical fiber type wavelength conversion element shown in FIG. 1 will be described. Inner diameter 2.5 μm, outer diameter 1.
SF4 glass with a length of 0 mm and a length of 50 mm (made by Hoya Glass)
The capillary was filled with the DAN melt, and the single crystal was grown as a core by cooling to prepare an optical fiber type optical wavelength conversion element. The core growth method is a method in which a molten liquid of DAN is sucked up by utilizing a capillary phenomenon, and then a crystal is grown from the end by the Bridgman method (for a detailed manufacturing method, refer to JP-A-3-111826).

Two pieces of this optical fiber type optical wavelength conversion element were cut out to a length of 5 mm, and thereafter, an aluminum thin film as a light shielding film was formed on the side surface of one glass clad by a vacuum deposition method. Nd: YAG is added to the core of each optical wavelength conversion element.
When laser light with a wavelength of 1.064 μm was incident, converted light with a wavelength of 0.532 μm was emitted from the fiber emission end into the air.

A performance deterioration test was conducted by leaving the element with and without the light-shielding film under a white lamp of 100 W for a long period of time, and a performance deterioration test was performed. The conversion efficiency decreased exponentially with the number of days. The results of this performance deterioration test are shown in FIG. Next, using DMNP instead of DAN as the material of the core, an optical wavelength conversion device similar to the above was manufactured, and the same performance deterioration test was conducted. As a result, the conversion efficiency of the device with the light-shielding film was hardly deteriorated. In addition, the conversion efficiency of the device without the light-shielding film decreased exponentially with the number of days. The results of this performance degradation test are shown in FIG.

The present invention is not limited to the above-described embodiment. For example, of the light incident end face 44 of FIG. 1, a portion other than the end face 41a of the core 41, which is the light incident region, that is, the end face 42a of the clad 42 is formed. May be covered with a light-shielding layer, and a part of the light-incident end surface 54 of FIG. 3 excluding the end surface 51a of the channel 51, which is a light-incident region, that is, the end surface 52a of the clad 52 may be covered with the light-shielding layer. .. This is because in any case, light does not enter the end surface of the clad. Furthermore, it goes without saying that it is not necessary to provide a light-shielding layer on a portion where external light is not likely to enter, such as a mounting surface of the light wavelength conversion element on the substrate.

[0018]

As described above, according to the optical wavelength conversion element of the present invention, the absorption of harmful light into the organic nonlinear optical material forming at least one of the optical waveguide portion and the clad can be minimized. It is possible to prevent deterioration of the light wavelength conversion element due to photolysis of the organic nonlinear optical material, and it is possible to extend the life of the light wavelength conversion element.

[Brief description of drawings]

FIG. 1 is a perspective view showing a basic configuration of a light wavelength conversion element according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a basic configuration of a light source device to which the light wavelength conversion element is applied.

FIG. 3 is a perspective view showing a basic configuration of a light wavelength conversion device according to another embodiment of the present invention.

FIG. 4 is a graph showing a result of a performance deterioration test of the light wavelength conversion element.

FIG. 5 is a graph in which the light transmittance of an organic nonlinear optical material is measured.

[Explanation of symbols]

 4,5 Optical wavelength conversion element 41 Core 42,52 Clad 43,53 Light-shielding layer 51 Channel

Claims (1)

[Claims] 1. An optical waveguide section and a clad having a refractive index lower than that of the optical waveguide section. At least one of the optical waveguide section and the clad is made of an organic nonlinear optical material, and is incident on the optical waveguide section. In a light wavelength conversion element that generates light whose wavelength has been converted from light, a light-shielding layer is provided on the outer surface of the light wavelength conversion element excluding the light incidence area of the light incidence end surface and the light emission area of the light emission end surface or a part of the outer surface. An optical wavelength conversion element characterized by being provided.