JPH10133043A - Waveguide type optical parts and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide waveguide type optical parts which are safe and excellent in long-term reliability and a manufacturing method therefor. SOLUTION: The waveguide type optical parts 1 having locally changed refractive index can be obtained by irradiating at least a part of a core region 3 which is added with a photosensitizer or an intensifier and is covered with a clad region 4 having lower refractive index than that of the core region 3 of the waveguide type optical parts 1 with UV ray. The photosensitizer added with at least one component among gold, silver, copper and silver halide is used and the intensifier added with cerium or oxide thereof is used. By applying the method to the waveguide type optical parts consisting essentially of quartz series materials, the optical parts with low loss and high reliability can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a waveguide type optical component in which a core region having a higher refractive index is covered with a cladding region having a lower refractive index than the core region, and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the spread of communication systems using light, development of optical components with lower loss and higher reliability has been actively pursued. In particular, a planar optical waveguide type optical component has attracted the most attention as a highly integrated optical circuit element because it can form a complicated circuit on a substrate in addition to its low loss property. In these planar optical waveguide type optical components, a light propagation region called a “core region” having a high refractive index is formed on a silicon substrate with a thermal oxide film or a quartz substrate, and this core region is further formed by a cladding region having a lower refractive index. It is common to take a covered structure.

In particular, the material composition of the core region is excellent in compatibility with an optical fiber, and silicon oxide glass doped with germanium, which has been proven as a low-loss material, is considered to be effective.

On the other hand, in recent years, research has been actively conducted to locally change the refractive index of a core region by irradiating ultraviolet rays using a germanium-doped quartz optical fiber. Although there are still many unclear points about the mechanism of the change in the refractive index due to ultraviolet irradiation, the following two points can be cited as causes of the change in the refractive index.

(1) First, in silicon oxide glass to which germanium is added, silicon is more easily oxidized than germanium, so that a part of germanium cannot be combined with oxygen, and an oxygen deficiency defect is weakly bound between germaniums. . When this part is irradiated with high-energy ultraviolet rays, the bonds between germaniums are broken, and electrons of germanium move from the valence band to the conduction band. The transition of electrons causes light of a wavelength different from that of germanium oxide to be absorbed, and the refractive index changes according to the Kramers-Kronig relationship.

[0006] However, this theory alone cannot explain a change in the refractive index of as much as 10 ^-3 . Therefore, recently, it is common to think that the influence of the density change due to the defect change is the main mechanism.

That is, the bonding of oxygen-deficient defects weakly bonded between germaniums is broken by ultraviolet absorption, and the network structure of the glass in the vicinity thereof shrinks to locally increase the density.
As a result, it is considered that the refractive index increases by the amount of the density change.

(2) If a refractive index is periodically changed in the propagation region, that is, the core region of the optical fiber, it becomes a grating (diffraction grating) and can be used as a filter that reflects only a specific wavelength.

Such an optical component is called a fiber grating, and is extremely small in size as compared with a conventional bulk type diffraction grating, and can be easily connected to another optical fiber. If this technology is applied, it can be used as an optical component having various functions such as a single-frequency oscillation laser, optical pulse compression / shaping, and dispersion compensation, in addition to a function as a filter for simply separating wavelengths. In addition to the field of optical communication, it is considered to be widely applied in the fields of measurement and information processing as sensors and memories.

[0010]

However, the above-mentioned prior art has the following problems.

First, the natural photosensitivity of a silicon oxide glass waveguide (fiber) doped with germanium is too large to give a photo-induced refractive index change (Δn> 10 ⁻³ ) necessary for application to an optical component. There is a problem that it is too small.

Therefore, methods such as a hydrogen loading method and a frame brushing method have been proposed to increase the photosensitivity inherent in optical fibers. All of these remedies increase the photosensitivity by diffusing and filling hydrogen in the core region.

In the hydrogen loading method, an optical fiber is exposed to a high-pressure, high-purity hydrogen atmosphere for a long time,
This is a method of diffusing and filling hydrogen into an optical fiber. Hydrogen loading usually takes about one week under a pressure of 100 to 200 atm, has low production efficiency, and requires careful handling.

The flame brushing method is a method in which hydrogen is diffused in an optical fiber by brushing the optical fiber with a flame of an oxyhydrogen burner. In this method, hydrogen diffusion and filling are performed in a short time, but the shape of the core region itself is deformed due to exposure to high temperature, or germanium as a dopant diffuses to the peripheral portion due to heat, thereby refracting the core region. There is a problem that the rate distribution changes greatly. The use of such an optical waveguide increases the loss and makes it very difficult to obtain desired characteristics.

Further, although the sensitizing effect of filling the core region with hydrogen causes a change in refractive index sufficient for practical use, long-term reliability has not been sufficiently studied. Depending on the use environment or the use period, hydrogen charged in the core region may diffuse to the outside and become unusable. In particular, when used as a communication optical component, it is necessary to sufficiently guarantee long-term reliability.

It is an object of the present invention to solve the above-mentioned problems and to provide a waveguide-type optical component which is safe and has excellent long-term reliability and a method of manufacturing the same.

[0017]

In order to achieve the above object, a waveguide type optical component according to the present invention comprises a waveguide type optical component in which a core region having a higher refractive index is covered by a cladding region having a lower refractive index than the core region. In the optical component, the core region is one in which at least one element of gold, silver, and copper is added, and at least part of the core region is irradiated with ultraviolet rays, and the refractive index is locally changed.

In order to achieve the above object, a method of manufacturing a waveguide-type optical component according to the present invention comprises manufacturing a waveguide-type optical component by covering a core region having a higher refractive index with a cladding region having a lower refractive index than the core region. In the method, after adding at least one element of gold, silver, and copper to the core region, at least a part of the core region to which these elements are added is irradiated with ultraviolet light to locally change the refractive index. is there.

In the present invention, in addition to the above constitution, silver added to the core region is preferably added as any one of silver chloride, silver bromide and silver iodide.

In the present invention, in addition to the above structure, it is preferable to add cerium to the core region.

The waveguide-type optical component and the method of manufacturing the same according to the present invention can obtain a highly sensitive photoinduced refractive index change without performing high-pressure hydrogen treatment.

According to the present invention, the refractive index is locally changed by irradiating a core region to which a photosensitizer or a sensitizer is added with ultraviolet rays, and gold, silver, copper or silver halide is used as a photosensitizer. A sensitizer to which at least one component is added and a sensitizer to which cerium or its oxide (ceria) is added are used.

By applying the present invention to a waveguide type optical component using a quartz-based material as a main component, a highly reliable optical component with low loss can be realized.

Here, elements such as gold, silver, and copper function as photosensitive metals. That is, when a glass material to which a small amount of these metals is added is irradiated with high-energy ultraviolet rays, it is exposed to light and neutral metal atoms are precipitated. The photosensitivity depends on the type and amount of metal, but when cerium is added as a sensitizer, the effect is particularly remarkable. When ultraviolet light is irradiated on the glass to which the photosensitive metal and cerium are added, photoelectrons are emitted from Ce ³⁺ , and these are captured by the photosensitive metal ions and the coexisting Ce ⁴⁺ capture center. Subsequently, the metal ions combine with the electrons captured by Ce ⁴⁺ to form metal atoms, and further, these metal atoms and the neutral metal capturing the photoelectrons aggregate to form metal colloids.

When the silver halide is irradiated with ultraviolet rays, a neutral silver colloid is formed in the silver halide colloid ions. Thus, high photosensitivity can also be obtained by adding silver ions in the form of silver halide. The degree of this photosensitivity differs depending on the wavelength and the type of halogen, and the photosensitive layer becomes sensitive to light having a long wavelength in the order of silver iodide, silver bromide, and silver chloride.

The change in the defect caused by the neutral metal atoms formed in this manner causes a change in local density and internal stress, thereby causing a change in the refractive index. However, since the addition of an excessive amount of the metal element causes light absorption, it must be added in a small amount in the range of 0.01 to 0.1 wt% in the core region.

The change in the refractive index by the conventional ultraviolet irradiation was effective only for the silicon oxide glass to which germanium was added due to its mechanism.

However, according to the present invention, the dopant added to the core region in order to increase the refractive index is not limited to germanium, and a change in the refractive index can be confirmed even when phosphorus or titanium is added.

The addition of the photosensitive metal element and the sensitizer as described above can be performed by a sputtering method, a vapor deposition method, or an ion implantation method. In particular, it is applicable to a planar optical waveguide type optical component using a planar substrate.

[0030]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a waveguide type optical component according to the present invention.

In the waveguide type optical component 1 shown in FIG. 1, a core region 3 having a high refractive index, which is a light propagation region, is formed on a quartz substrate 2, and a core region 3 having a lower refractive index than the core region 3 is formed by a core. Region 3 is covered. The size of the core region 3 is about 6
μm × 6 μm, but is not limited to this. The core region 3 is obtained by adding 8 wt% of germanium oxide as a dopant for increasing the refractive index to silicon oxide glass as a main component. In the core region 3, 0.01 wt% of silver is added as a photosensitive metal by ultraviolet irradiation, and cerium oxide (ceria) is used as a sensitizer in an amount of 0.03 w%.
t% is added. Since the addition of an excessive amount of a photosensitive metal or a sensitizer causes light absorption, the amount added to the core region 3 must be kept within a range of 0.1 wt% or less.

The cladding region 4 contains silicon oxide glass as a main component, and phosphorus and boron are added. This is because phosphorus has a property of increasing the refractive index and boron has a property of decreasing the refractive index. By adjusting the component ratio between phosphorus and boron, the refractive index of the cladding region 4 can be made substantially equal to that of the quartz substrate 2. That is, the core region 3 is covered with the quartz substrate 2 having a lower refractive index and the cladding region 4, and the quartz substrate 2 functions as a lower cladding.

The core region 3 is processed into a rectangular cross section by film formation by sputtering and reactive ion etching after waveguide patterning. The material composition of the target material used for sputtering is prepared in accordance with the composition of the core region 3. At this time, since the element relating to photosensitivity takes a plurality of valences in the glass, the melting atmosphere for manufacturing the target material is important.

In particular, photosensitive metals have low ionic solubility,
Care must be taken so that the atmosphere is not reduced because it is easily reduced.

On the other hand, in the cladding region 4, fine particles for a glass film having a low refractive index are deposited by a flame hydrolysis reaction over the entire core region 3 processed into a rectangular cross-sectional shape on the quartz substrate 2. By sintering at a high temperature, the fine particles are turned into a transparent glass. By adding phosphorus and boron, sintering can be performed at a temperature lower than the deformation temperature of the quartz substrate 2.

Although the quartz substrate 2 having the function of the lower clad is used for the waveguide type optical component shown in FIG. 1, the present invention is not limited to this, and a silicon substrate may be used. However, when a silicon substrate is used, a silicon oxide layer must be formed on the silicon substrate to avoid absorption by the substrate and adjust the refractive index. This silicon oxide can be formed by sputtering or vapor deposition, but can also be formed by thermal oxidation of a silicon substrate.

Although silver was used as the photosensitive metal by irradiation with ultraviolet rays, similar changes in the refractive index were confirmed when gold, copper, or silver halide such as silver chloride was used.

FIG. 2 is a conceptual diagram of a method of manufacturing a waveguide type optical component according to the present invention. FIG. 2 particularly describes a case where a grating is formed.

A waveguide type optical component 1a in which at least one of gold, silver and copper is added to the core region is mounted on an XY stage 5, and a grating pattern is written on the waveguide type optical component 1a. Put the phase mask 6 that was set.
Excimer laser light (ultraviolet light) 8 shaped into an appropriate beam shape by a lens 7 from above the phase mask 6-
Irradiate in the Z direction. When the phase mask 6 is irradiated with the excimer laser light 8, the refractive index of the core region of the waveguide type optical component 1 a is locally changed by the excimer laser light 8 transmitted through the transmission part of the phase mask 6, as shown in FIG. The obtained waveguide type optical component 1 is obtained.

The grating length obtained by the change in the refractive index due to the exposure can be determined by moving the lens 7 and the mirror 9 in the X and Y directions to scan with the excimer laser beam 8, or
It is adjusted by moving the stage 5 in the XY directions together with the waveguide type optical component 1a. As a result of forming the grating in the optical waveguide in this way, a waveguide-type optical component having a grating with a length of 5 mm, a reflectance at a wavelength of 1535 nm of 99.8% or more, and a light-induced refractive index change of 10 ^-3 or more is obtained. be able to.

As described above, according to the present invention, the refractive index can be locally changed by irradiating at least a part of the core region to which at least one of gold, silver and copper is added with ultraviolet rays. It does not require hydrogen filling such as the hydrogen loading method and the frame brushing method. As a result, there is no need for a manufacturing process that requires long-term and careful attention for safety or an overheating manufacturing process that deteriorates the optical characteristics of the waveguide. Further, since the refractive index is not changed by the hydrogen treatment, there is no possibility that hydrogen diffuses into the air and loses its function.
Therefore, an optical component having excellent long-term reliability can be obtained. Further, the present invention can utilize a conventional manufacturing method, and can be easily applied to a planar optical waveguide type optical component having various functions.

[0043]

In summary, according to the present invention, the following excellent effects are exhibited.

At least a part of the core region in the waveguide type optical component in which at least one element selected from gold, silver and copper is covered by a cladding region having a lower refractive index than the core region is irradiated with ultraviolet rays. Thereby, since the refractive index of the core region can be locally changed, it is possible to provide a waveguide-type optical component that is safe and has excellent long-term reliability and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a sectional view of a waveguide type optical component according to the present invention.

FIG. 2 is a conceptual diagram of a method for manufacturing a waveguide-type optical component according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 waveguide type optical component 2 quartz substrate 3 core region 4 cladding region

Claims (5)

[Claims] 1. A waveguide type optical component in which a core region having a high refractive index is covered with a cladding region having a lower refractive index than the core region, wherein the core region has at least one element selected from gold, silver and copper. A waveguide-type optical component, wherein the refractive index is locally changed by being added and at least partially irradiated with ultraviolet rays. 2. A method of manufacturing a waveguide-type optical component in which a core region having a high refractive index is covered with a cladding region having a lower refractive index than the core region, wherein the core region includes at least one element selected from gold, silver, and copper. A method of manufacturing a waveguide-type optical component, which comprises irradiating at least a part of a core region to which these elements are added with ultraviolet rays to locally change a refractive index. 3. The method according to claim 2, wherein the silver added to the core region is added as any one of silver chloride, silver bromide, and silver iodide. . 4. The method according to claim 2, wherein cerium is added to the core region. 5. The core region has a refractive index higher than that of the cladding region by adding at least one component of germanium, phosphorus or titanium oxide to glass containing silicon oxide as a main component. 5. The method of manufacturing a waveguide-type optical component according to any one of items 1 to 4.