JPH07244308A - Optical wavelength conversion element and its production - Google Patents

Abstract

PURPOSE:To obtain an optical wavelength conversion element constituted to realize higher efficiency, higher reliability and lower cost. CONSTITUTION:Substrate glass 4a on which an antireflection film 5 for basic waves is formed by a vacuum vapor deposition method is adhered by a UV curing resin 3a to the incident end of a glass fiber consisting of two layers; a core 1 and a clad 2. Similarly, substrate glass 4b on which an antireflection film 6 of second higher harmonic waves is formed by a vacuum vapor deposition method is adhered by a UV curing resin 3b at the exit end. The antireflection film 5 of the basic waves is formed at the incident end face, by which scattering of the basic waves at the incident end face and the loss by reflection are suppressed. The loss of the radiated second higher harmonic waves by scattering and reflect at the exit end face is prevented by the antireflection film 6 and the efficient taking out of the second higher harmonic waves is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light wavelength conversion element and a method for manufacturing the same, and more particularly, as a laser light source which can be used in light-applied consumer equipment such as optical disks and laser printers, or commercial equipment And a method for manufacturing the same.

[0002]

2. Description of the Related Art As a light source for pickup of optical discs, compact discs, laser discs, magneto-optical discs, etc., conventionally, mainly from red to infrared (650 nm to 83 nm).
Although a semiconductor laser having a wavelength of 0 nm) is used, studies are currently underway to use a laser having a shorter wavelength as a light source in order to improve the recording capacity. One is a II-VI group compound semiconductor laser capable of direct blue oscillation, and the other is an SHG using an existing semiconductor laser.
(Second Harmonic Generation: Second harmonic generation)
The element is intended to obtain a laser beam having a wavelength of half of that.

In particular, a short wavelength light source using an SHG element is currently under active research and development because of its practicality. S
In order to realize highly efficient wavelength conversion in the HG element, the energy of the fundamental wave incident on the organic nonlinear optical crystal should not be attenuated as much as possible, and the second harmonic wave emitted from the nonlinear optical crystal should be effectively extracted to the outside of the element. In addition, it is important to prevent the deterioration of the organic nonlinear optical crystal. For this reason, it has been attempted to reduce the energy loss due to reflection and scattering at the time of entering and exiting the light in the wavelength converting element of the waveguide type or the resonator type wavelength converting element using the bulk crystal to improve the efficiency. ing.

For example, the "optical wavelength conversion element" described in Japanese Patent Application Laid-Open No. 2-254426 is on the end face of the optical wavelength conversion element including the end face of the organic nonlinear optical material or on the surface of the bulk crystal of the organic nonlinear optical material. By providing the circuit breaker, the sublimation and metamorphosis of the organic nonlinear optical material are prevented.

In addition, according to the conventionally devised method regardless of the waveguide type or bulk type, an antireflection film such as a dielectric multilayer film or a single layer film is directly formed on the surface of the organic nonlinear optical crystal. When forming such a dielectric film, a vacuum vapor deposition method is generally used, and an organic nonlinear optical crystal must be installed in a vacuum chamber when directly forming a film. However, there is a problem that the organic crystal is damaged during film formation, and although it is possible to achieve high efficiency in principle, it was impossible to realize in the device manufacturing process. Although attempts have been made to realize a technique that protects an organic crystal and prevents reflection as described above, it has been difficult with the conventional technique.

Further, the reflection of the fundamental wave from the end face of the crystal causes the fluctuation of the intensity or the destruction of the primary light source when the reflected light returns to the primary light source. Conventionally, to prevent this,
An isolator such as a Faraday rotator and a primary light source and an S
By inserting between the HG elements, the return light due to reflection was shielded. However, in this case, there is a drawback that the number of parts increases, leading to high cost.

[0007]

The recording density of the optical recording system can be improved by using the SHG element as a light source as described above, but it is important to improve the efficiency of the SHG element. Therefore, attempts have been made as described in the above-mentioned prior art, but it is difficult to actually manufacture the element, and it is difficult to put it into practical use in the manufacturing process. In addition to high efficiency, the return light due to the reflection of the fundamental wave from the incident end face of the SHG element also adversely affects the primary light source,
Heretofore, improvements have been attempted as described above with respect to antireflection or shielding of return light by reflection. However, it was difficult to realize both in terms of manufacturing method and cost.

The present invention has been made in view of the above circumstances, and has a structure in which a glass substrate on which a dielectric multilayer film or a single layer film is formed is attached to the input / output end face of an organic nonlinear optical crystal. It is an object of the present invention to provide an optical wavelength conversion element and a method for manufacturing the same, which are intended to realize high efficiency, high reliability, and low cost.

[0009]

According to the present invention, in order to achieve the above object, (1) the wavelength of laser light is halved.
In an optical wavelength conversion element using a harmonic wave generation element, a core formed of an organic nonlinear optical material having a high second harmonic wave generation efficiency in a central part, and a core having a refractive index lower than that of the core and formed around the core. In order to protect the clad layer formed of a material having a high transmittance of harmonic light and the organic non-linear optical material in the central portion, it is provided on the end face where the fundamental wave is incident and the end face where the second harmonic is emitted, respectively. And a high-transmissivity plate material, and (2) antireflection for preventing reflection of the fundamental wave on the surface of the high-transmissivity plate material attached to the element end face on which the fundamental wave is incident. With the provision of a membrane,
(3) An antireflection film for preventing reflection of the second harmonic is provided on the surface of a plate material having a high light transmittance, which is attached to the end face of the element from which the second harmonic is emitted, or (4) In the method of manufacturing an optical wavelength conversion element having a resonator structure using a bulk crystal of an organic nonlinear optical material, in the end surface of the bulk crystal on which the excitation light is incident and the end surface on which the second harmonic wave is emitted, a light transmissive element is used. Formed by attaching a high plate material, and having the plate material end face of the adhered high light transmitting plate on which the excitation light is incident, has both the function of preventing the reflection of the excitation light and the effect of the total reflection of the second harmonic. The present invention is characterized in that a film is formed and a film having both the total reflection of excitation light and the antireflection of the second harmonic is formed on the end surface of the plate material from which the second harmonic is emitted.

[0010]

A feature of the light wavelength conversion element is that laser light having a wavelength in the 400 nm range can be easily obtained. However, in order to achieve high efficiency (high power), there are the above-mentioned problems. In order to solve these problems, the present invention firstly has a structure in which a plate material that protects the organic nonlinear optical crystal and prevents the reflection of the end face is attached to the incident end face of the SHG element. In order to prevent reflection of the fundamental wave, a dielectric multilayer film or a single layer film is previously formed on this plate material by a vacuum evaporation method. This is attached to the incident end face of the SHG element with an adhesive for optical use such as epoxy resin. Similarly, an antireflection film for preventing reflection of the second harmonic is formed in advance on the emitting end of the second harmonic and is attached to the emitting end.

With the structure of the present invention, first,
There is an effect that the contact between the organic nonlinear optical material and the air on the input / output end face of the element can be shielded, and thereby the deterioration of the organic nonlinear optical material due to sublimation or modification can be prevented. Next, an anti-reflection film attached to the input / output end face of the element has the function of preventing reflection from the incident end face, allowing the fundamental wave to be efficiently coupled to the nonlinear optical crystal, and reflecting from the incident end. Since the amount is small, it has an effect of preventing element deterioration due to the return light to the primary light source.
The antireflection film attached to the emitting end face is basically different from the one attached to the incident end face, and the second harmonic generated by the optical wavelength conversion element can be effectively taken out to the outside of the element without causing loss due to reflection inside the element. Has an effect. As described above, as the function relating to the element performance, not only preventing the characteristic deterioration of the entire optical wavelength conversion element including the primary light source and the organic nonlinear optical material, but also providing a highly efficient wavelength conversion characteristic, and Second efficiently generated
Since the harmonics can be taken out of the device, it is possible to realize an optical wavelength conversion device with high efficiency, long life and high reliability.

Further, in the method of manufacturing an optical wavelength conversion element according to the present invention, the antireflection films for the fundamental wave and the second harmonic wave are individually formed on the surface of the plate material first, and then S
The manufacturing process of attaching to the input / output end face of the HG element is adopted, and as described in the prior art, the sublimation of the crystal at the time of film formation and the case of directly forming a film on the surface of the organic nonlinear optical crystal are performed. It has an effect of preventing deterioration such as denaturation. Further, the adoption of this manufacturing process is very important in manufacturing a practical optical wavelength conversion element.

In addition, in order to improve the recording density of an optical recording system represented by an optical disk or a magneto-optical disk, the light source is shorter than the conventional one, in addition to the improvement on the system side such as utilizing super-resolution. It is useful to use a wavelength laser. Furthermore, in the optical wavelength conversion element of the present invention, as described above, a highly practical optical wavelength conversion element can be provided by improving the manufacturing method while improving efficiency, environment resistance, cost reduction, long life, and reliability improvement. It is possible to manufacture.

[0014]

Embodiments will be described below with reference to the drawings. FIG. 1 is a configuration diagram for explaining an embodiment of an optical wavelength conversion device according to the present invention, which is a configuration diagram of a fiber waveguide type SHG device. In the figure, 1 is a core, 2 is a clad, 3
a and 3b are ultraviolet curable resins, 4a and 4b are substrate glass,
Reference numeral 5 is an antireflection film (for a fundamental wave), 6 is an antireflection film (for a second harmonic), 7 is a fundamental wave, and 8 is a second harmonic. As a basic configuration, a glass fiber consisting of two layers of a core 1 and a clad 2 is bonded at the incident end with a substrate glass 4a on which an antireflection film 5 of a fundamental wave is formed by a vacuum deposition method with an ultraviolet curable resin 3a. Similarly, at the exit end, the substrate glass 4b is provided with a second harmonic antireflection film 6 formed by a vacuum vapor deposition method and bonded with an ultraviolet curable resin 3b.

By forming the antireflection film 5 for the fundamental wave on the incident end face, the loss due to scattering and reflection of the fundamental wave on the incident end face is suppressed, and therefore the fundamental wave 7 coupled in the core 1 very efficiently. Is propagated while being confined in the core 1 having a high refractive index, and the second harmonic wave 8 generated by the interaction with the nonlinear material of the core 1 is clad at an angle determined by the mutual refractive index of the core 1 and the clad 2. 2 is emitted inside.
The radiated second harmonic propagates through the cladding layer 2 and is taken out from the emitting end face. At this time, the second harmonic antireflection film 6 formed on the emitting end face causes the second harmonic at the emitting end face. It is possible to efficiently extract the second harmonic without loss due to scattering and reflection.

In this embodiment, FD11 is used as the cladding glass.
(Heavy flint glass from Schott, USA), 3,5-dimethyl-1- (4-nitrophenyl) pyrazole (PRA) as the core material, fiber waveguide type SHG with a core diameter of 1.4 μm and an outer diameter of 1 mm. A device was used. A MgF ₂ single layer film (incident side film thickness: 0.16 μm, emission side film thickness: 0.08 μm) was used as the antireflection film for the fundamental wave and the second harmonic, which is a feature of the present invention.

FIG. 2 shows the wavelength dependence of the reflectance of the MgF ₂ single-layer antireflection film used in this example. From this result, it can be seen that the reflectance is suppressed to 1.5% or less on both the input and output sides, which contributes to the improvement of the coupling efficiency of the fundamental wave and the emission efficiency of the second harmonic.

3 (a) to 3 (c) show SH according to the present invention.
It is a figure which shows one Example of the manufacturing method of G element, The reference number in a figure is the same as FIG. First, as shown in FIG.
A glass substrate 4a having both surfaces optically polished and sufficiently removed of oil and water by washing is prepared, and an incident fundamental wave antireflection film 5 is formed on the glass substrate 4a by a vacuum deposition method. Similarly, as shown in FIG. 2B, another glass substrate 4b is prepared, and the second harmonic antireflection film 6 is formed by the vacuum evaporation method. Next, as shown in FIG. (C), a hollow capillary having FD11 as a cladding glass is filled with 3,5-dimethyl-1- (4-nitrophenyl) pyrazole as a core material to crystallize a fiber. An ultraviolet curing resin 3a, 3b, or an adhesive such as an epoxy resin is applied to both end faces of the fiber, and a glass substrate 4a with an antireflection film for a fundamental wave prepared in advance is applied to the incident side end face as the second harmonic. The glass substrate 4b with the antireflection film for waves is adhered and sealed to the end face on the emission side. As described above, the manufacturing method according to the present invention makes it possible to manufacture an organic nonlinear optical crystal without exposing it to a vacuum.

The core material used in this example is 3,
Not limited to 5-dimethyl-1- (4-nitrophenyl) pyrazole, MNA (dimethylnitroaniline), DAN
(4- (N, N-dimethylamino) -3-acetoamindoni
The same effect can be obtained by using other organic nonlinear substances such as trobenzene). Regarding the clad material,
Any material may be used as long as it has a lower refractive index than the core material, and is not limited to the material used in this embodiment. Also, the antireflection film for the fundamental wave and the second harmonic need not be limited to the dielectric multilayer film or the single layer film as long as the transmission characteristics at each wavelength are satisfied. Similarly, as the adhesive for the glass substrate and the element, any material having a high transmittance of the fundamental wave and the second harmonic can be used without being limited to this embodiment.

FIG. 4 is a block diagram of a resonator type SHG element using a bulk crystal according to the present invention. In the figure, 9 is an organic nonlinear optical crystal, 10 is a semiconductor laser chip, 11 is a heat sink, and 12 is a semiconductor laser beam. Antireflection film (solid laser medium pumping light total reflection film), 13 is solid laser medium, 14
a, 14b are adhesives, 15a, 15b are glass substrates, 1
Reference numeral 6 is a solid laser medium pumping light antireflection film (second harmonic total reflection film), 17 is a solid laser medium pumping total reflection film (second harmonic antireflection film), 18 is a semiconductor laser light, and 19 is a solid laser medium. Excitation light, 20 is the second harmonic.

The semiconductor laser chip 1 has a basic structure.
0, a solid-state laser medium 13 and an organic nonlinear optical crystal 9. The semiconductor laser chip 10 used is for exciting the solid-state laser medium 13 and emits a semiconductor laser light 18 having an oscillation wavelength of 809 nm. In the present embodiment, YVO ₄ is used as the solid-state laser medium 13, and after both surfaces are optically polished, the incident side end face is anti-reflective with respect to the laser beam of 809 nm, and the action of total reflection is performed with respect to the excitation light generated by absorption excitation. The dielectric multi-layered film (12) having is formed by a vacuum deposition method.

Further, an organic nonlinear optical crystal (in this example, 3,5-dimethyl-1- (4-nitrophenyl) pyrazole was prepared similarly to Example 1 in FIGS. 1 and 3 described above. (A bulk crystal is used), and an antireflection film 16 for 19 wavelengths of excitation light excited by the solid-state laser medium 13 in the substrate glass 15
Which is formed by a vacuum vapor deposition method is adhered with an ultraviolet curable resin 14, and at the emitting end, a substrate glass 15 on which an antireflection film 17 for the second harmonic is formed by a vacuum vapor deposition method is used as an ultraviolet curable resin 14. It is composed by bonding with.

Further, in this case, the antireflection film 16 has an antireflection function for the excitation light, but is designed so as to act as a total reflection film for the second harmonic generated in the organic nonlinear crystal. Has been done. Similarly, the antireflection film 17 has an antireflection effect on the second harmonic, but is designed to act as a total reflection film on the excitation light.

By constructing the optical wavelength conversion element in this way, the pumping light 1 excited by the solid-state laser medium 13
9 has a resonance structure between the incident end face of the solid-state laser medium 13 and the emitting end face of the organic nonlinear optical crystal 9, the pumping light power inside the resonator is amplified, and the efficiency of the second harmonic generated is greatly improved. Will contribute. The cavity length can be easily adjusted by adjusting the distance between the solid-state laser medium 13 and the organic nonlinear optical crystal 9. Further, the semiconductor laser light, the excitation light by the solid-state laser medium, the antireflection film for the second harmonic, and the total reflection film, which are the features of the present invention, are the two-layer periodic structure of Na ₃ AiF ₆ and ZnS (optical). A dielectric multilayer film having a film thickness λ / 4) was used.

FIGS. 5A to 5C show SH according to the present invention.
It is a figure which shows the other Example of the manufacturing method of G element, The reference number in a figure is the same as FIG. It can be manufactured by the same process as in the first embodiment. First, as shown in FIG. 1A, a glass substrate 15a is prepared by optically polishing both surfaces and sufficiently removing oil and water by washing.
An anti-reflection film for the excitation light and a total reflection film 16 for the second harmonic are formed on 5a by a vacuum evaporation method. Similarly, as shown in FIG. 6B, another glass substrate 15b is prepared, and the antireflection film for the second harmonic and the total reflection film 17 for the excitation light are formed by the vacuum evaporation method.

Next, as shown in FIG. 3C, crystals are grown in advance by a solvent evaporation method, and 3,5-dimethyl-
Bulk crystal of 1- (4-nitrophenyl) pyrazole 9
Of the glass substrate 15a, 1 prepared in the above manner by applying an adhesive such as an ultraviolet curable resin 14a, 14b or an epoxy resin to both end faces of the bulk crystal 9.
5b is adhered to each of the incident side and the emitting side, and then the semiconductor laser and the solid-state laser medium are combined to complete the manufacturing. As described above, the manufacturing method according to the present invention makes it possible to manufacture an organic nonlinear optical crystal without exposing it to vacuum.

In the case of the resonator type optical wavelength conversion element, unlike the first embodiment, the entire organic nonlinear optical crystal cannot be completely shielded from the atmosphere, and the glass substrate can protect at least both ends of the input and output. In this embodiment, in order to secure the stability of the device, it is necessary to purge the inside of the device with an inert gas such as Ar or N ₂ because it is only the surface.

The bulk material used in this example is
The same effect can be obtained by using not only 3,5-dimethyl-1- (4-nitrophenyl) pyrazole but also other organic nonlinear substances such as chalcone and DAN. Further, the semiconductor laser light, the excitation light by the solid-state laser medium, the antireflection film for the second harmonic, and the total reflection film are limited to the dielectric multilayer film as long as the transmission or reflection characteristics at each wavelength are satisfied. No need. Similarly, the adhesive for the glass substrate and the element can be used as long as it is a material having a high transmittance for the excitation light and the second harmonic by the solid-state laser medium, without being limited to this embodiment.

[0029]

As is apparent from the above description, in the wavelength conversion element according to the present invention, in the fiber type, the core material can be protected, the life is longer, the reliability is higher than the conventional one, and the stability is stable. The effect of being excellent can be expected. In addition, since the fundamental wave can be efficiently coupled into the fiber and the generated second harmonic can be efficiently extracted to the outside of the element, it is expected that the wavelength conversion efficiency of the optical wavelength conversion element can be improved. it can. Further, also in the resonator type, the same effect as that of the fiber type can be expected except for the direct protection of the organic nonlinear optical crystal. Furthermore, in the manufacturing method as well, it is possible to manufacture the organic nonlinear optical crystal directly without exposing it to a vacuum at the time of coating, and it is possible to improve the manufacturing yield of the wavelength conversion element and to apply the processes of conventional electronic devices and optical devices. Therefore, it can be manufactured at low cost, and the economic effect of the present invention is great. Further, it can be applied to an optical system as a short wavelength laser light source.

[Brief description of drawings]

FIG. 1 is a structural diagram for explaining an embodiment of an optical wavelength conversion device (fiber Cherenkov type SHG device) according to the present invention.

FIG. 2 is a reflection characteristic diagram of a single-layer antireflection film according to the present invention.

FIG. 3 Fiber type and resonator type SH according to the present invention
It is a figure for demonstrating the manufacturing method of a G element.

FIG. 4 is a structural diagram of a resonator type SHG element according to the present invention.

FIG. 5 is a drawing for explaining the manufacturing method of the resonator type SHG element according to the present invention.

[Explanation of symbols]

1 ... Core, 2 ... Clad, 3a, 3b ... Adhesive, 4a,
4b ... Glass substrate, 5 ... Fundamental wave antireflection film, 6 ... Second harmonic antireflection film, 7 ... Fundamental wave, 8 ... Second harmonic wave, 9 ... Organic nonlinear optical crystal, 10 ... Semiconductor laser chip, 11 ...
Heat sink, 12 ... Semiconductor laser light antireflection film (solid laser medium excitation light total reflection film), 13 ... Solid laser medium,
14a, 14b ... Adhesive, 15a, 15b ... Glass substrate, 16 ... Solid-state laser medium pumping light antireflection film (second harmonic total reflection film), 17 ... Solid-state laser medium pumping light total reflection film (second harmonic reflection) Prevention film), 18 ... Semiconductor laser light, 1
9 ... Solid-state laser medium excitation light, 20 ... Second harmonic wave.

Claims (4)

[Claims] 1. A light wavelength conversion element using a second harmonic generation element that halves the wavelength of laser light, wherein a core formed of an organic nonlinear optical material having a high second harmonic generation efficiency is provided in the central portion, A fundamental wave is incident on the periphery of the core in order to protect the clad layer formed of a substance having a lower refractive index than that of the core and having a high light transmittance of the second harmonic light, and the organic nonlinear optical material in the central portion. An optical wavelength conversion element comprising: a plate material having high light transmittance, which is provided on each of the end surface and the end surface from which the second harmonic wave is emitted. 2. An antireflection film for preventing reflection of a fundamental wave is provided on a surface of a plate material having a high light transmittance attached to an end face of an element on which the fundamental wave is incident.
The optical wavelength conversion element described. 3. An antireflection film for preventing reflection of the second harmonic is provided on the surface of a plate material having a high light transmittance, which is attached to the end face of the element from which the second harmonic is emitted. The optical wavelength conversion element according to claim 1. 4. The method for manufacturing an optical wavelength conversion device having a resonator structure using a bulk crystal of an organic nonlinear optical material, wherein the end face of the bulk crystal on which the excitation light is incident and the end face on which the second harmonic wave is emitted, Each plate is formed by attaching a plate material with high light transparency, and the end faces of the plate materials with high light transparency that are attached and on which the excitation light is incident prevent the reflection of the excitation light and totally reflect the second harmonic. And a film having both functions of total reflection of excitation light and antireflection of second harmonics are formed on the end surface of the plate material from which the second harmonics are emitted. Method for manufacturing wavelength conversion element.