JPH05226733A - Rare-earth element added glass waveguide and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a glass waveguide in which a film thickness and a refractive index are controlled and a rare-earth element is uniformly added by a method wherein a core glass composed of a specific oxide matter containing the rare- earth element is formed on the surface of a substrate. CONSTITUTION:When electron beams are substantially concurrently emitted to tablets 3a, 4a within evaporation sources 3. 4 from electron guns 5, 6, respectively, and each of the tablets 3a, 4a radially evaporates to mix within a chamber 2 as well as reach a plurality of substrates 8a to 8n located on the upper part within the chamber 2, so that a glass film composed of SiO2 and Ta2O5, may be formed on the surface. Here, by adjusting a current of the electron guns 5, 6, the annexing amount of a rare-earth element in a glass film can be adjusted by controlling an evaporation speed from the evaporation source. A control scope of the annexing amount can be realized ranging within several percentages from 100ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass waveguide containing a rare earth element and a method for manufacturing the glass waveguide.

[0002]

2. Description of the Related Art In recent years, attention has been paid to research and development for realizing a laser or an optical amplifier by adding a rare earth element into the core of a glass waveguide.

FIG. 3 shows a conventional example of a method of adding a rare earth element into the core of a glass waveguide. That is, a glass porous film for a core part on a substrate obtained in a step of forming a glass part for transmitting light and a glass optical waveguide film having a clad layer around the core part on the substrate is made to transition with a rare earth element. Immerse in a solution containing one or more kinds of elements selected from metallic elements, add the element to the core portion at a predetermined concentration, dry and sinter, and then photolithography and dry etching process on the surface of the core portion. This is a method for obtaining a rare earth element-doped glass waveguide for laser or optical amplifier by depositing a clad layer (JP-A-2-2508).
3 gazette).

[0004]

However, the above-mentioned conventional method for manufacturing a glass waveguide containing a rare earth element has the following drawbacks.

(1) It was difficult to uniformly add a rare earth element into the core portion. That is, since the above-mentioned method is a method of impregnating a liquid in the glass porous film, it has a concentration distribution in the thickness direction of the glass porous film,
The concentration gradient of the rare earth element in the core part caused a decrease in excitation efficiency.

(2) It has been difficult to add a large amount of rare earth element in the core portion.

(3) It is difficult to control the film thickness and the refractive index because it is a method of depositing a porous glass film and then sintering it to obtain transparent glass.

(4) Impurities are easily mixed in through the liquid,
It was difficult to reduce the loss.

Therefore, the present invention was devised to effectively solve the above problems, and its main purpose is to control the film thickness and refractive index, to uniformly add rare earth elements, and Another object of the present invention is to provide a rare earth element-doped glass waveguide in which a large amount of the rare earth element is added and which has high gain, and a manufacturing method thereof.

[0010]

To achieve the above object, the first invention is to form a core glass composed of SiO ₂ and Ta ₂ O ₅ containing at least one rare earth element on the surface of a substrate, The core glass is covered with a low refractive index layer, and the second invention is that the SiO ₂ and Ta ₂ O ₅ core glass containing at least one kind of the rare earth element are formed by an electron beam evaporation method. Further, the third invention is a method of forming Si on a substrate having a low refractive index layer by an electron beam evaporation method.
An integrated tablet of O ₂ and Ta ₂ O _{5 and} a tablet containing at least one rare earth element are simultaneously evaporated to form a SiO ₂ and Ta ₂ O ₅ glass film containing at least one rare earth element. A SiO ₂ and Ta ₂ O ₅ glass film containing at least one of the rare earth elements is processed into a substantially rectangular shape by photolithography and dry etching, and then the entire surface of the substantially rectangular glass film is coated with a low refractive index glass film. The fourth invention is the above-mentioned SiO ₂
Integrated tablet of Ta ₂ O ₅ and SiO ₂ and Ta ₂
This is formed by mixing O ₅ powder and then solidifying it into a predetermined shape by hot pressing.

[0011]

In the glass waveguide of the present invention, the core glass, which is a region through which light propagates, is composed of SiO ₂ and Ta ₂ O ₅ having substantially the same melting points, and at least one rare earth element is added to the core glass. The glass film for a core is formed by an electron beam evaporation method having two evaporation sources as its manufacturing method. That is, S
When powders of iO ₂ and Ta ₂ O ₅ are mixed, a tablet solidified by hot pressing is put, a tablet containing at least one rare earth element is put in the other evaporation source, and when these tablets are simultaneously irradiated with an electron beam, The vapor is on the substrate placed on the upper side of the electron beam evaporation system,
Since it is a method of forming a glass film, a glass film containing at least two kinds of rare earth elements and a refractive index controlling additive Ta ₂ O ₅ can be easily obtained. Moreover, the film thickness and the refractive index can be precisely controlled, and the rare earth element can be added at a high concentration. Further, by adjusting the current value of each electron beam over time, the composition in the thickness direction (that is, the refractive index and the concentration of the rare earth element added) can be controlled. The tablet placed in one of the evaporation sources is made of a material having a melting point difference of ± 200 ° C such as SiO ₂ and Ta ₂ O ₅ to eliminate the difference in evaporation rate, suppress cluster formation, and have a particle size of 1 μm or less. It is possible to obtain a transparent glass film having a small light scattering loss. Further, since there are no clusters having a grain size of 1 μm or more in the glass film, the dry etching can be uniformly performed, and a substantially rectangular core pattern with less etching roughness can be formed. Further, by manufacturing an optical waveguide using the substrate thus obtained, an optical waveguide having low loss and high gain characteristics can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an electron beam vapor deposition apparatus 1 used for producing a glass film for core of a rare earth element-added glass waveguide according to the present invention.

As shown in the drawing, two evaporation sources 3 and 4 formed in a vessel shape are arranged at the bottom of the chamber 2.
A block-shaped tablet 3a made of SiO ₂ and Ta ₂ O ₅ is placed in one evaporation source 3, and a block-shaped tablet containing at least one rare earth element in one evaporation source 4. 4a is included.

The tablet 3a in the evaporation source 3 is made of SiO.
_This is a block-shaped sintered body in which powders of ₂ and Ta ₂ O ₅ are mixed so as to have a desired weight% and hot-pressed so that the sintered density becomes 90% or more. Also, this Ta ₂
O ₅ is an additive for controlling the refractive index, and is 1 with respect to SiO ₂ .
It is added in an amount of 10 to 10% by weight.

Further, electron guns 5 and 6 are provided in the vicinity of the evaporation sources 3 and 4, and the tablets 3a and 4a in the evaporation sources 3 and 4 are irradiated with electron beams to evaporate them. ..

On the other hand, inside the chamber 2, a substrate holder 7 is provided above the evaporation sources 3 and 4, and a plurality of substrates 8a to 8n are attached to the substrate holder 7. There is. A heater 9 is provided above the substrate holder 7 to heat the plurality of substrates 8a to 8n attached to the substrate holder 7 within a range of 100 to 400 ° C.

An oxygen gas introduction system 10 and a vacuum exhaust system 11 are connected to the chamber 2, respectively, and the chamber 2 is evacuated by the vacuum exhaust system 11 to a (10 ⁻⁷ Torr) state. After that, oxygen gas is introduced from the oxygen gas introduction system 10, and the degree of vacuum is 5 × 10 ⁻⁴ to 5 × 10.
-The oxygen flow rate is adjusted so that it becomes ^-5 Torr.

A partition plate 1 is provided between the evaporation sources 3 and 4.
2 is provided to prevent evaporative substances generated from these evaporation sources 3 and 4 from mixing with each other.

Next, the operation of the present invention will be described.

When the tablets 3a and 4a in the evaporation sources 3 and 4 are irradiated with electron beams from the electron guns 5 and 6 at substantially the same time in the above-mentioned state,
As shown in the figure, the tablets 3a and 4a evaporate radially, and while mixing in the chamber 2, reach the plurality of substrates 8a to 8n located in the upper part of the chamber 2 and reach the surfaces thereof with SiO ₂ and Ta ₂ O. _A glass film consisting of ₅ will be formed. Here, the amount of the rare earth element added to the glass film can be easily adjusted by adjusting the currents of the electron guns 5 and 6 to control the evaporation rate from the evaporation source 3. That is, the addition amount of the rare earth element in the glass film can be easily controlled by adjusting the evaporation rate, and the control range of the addition amount is 100.
It can be realized in the range of ppm to several%. For example, as a result of putting a tablet of Er ₂ O ₃ into the evaporation source 3 and making a glass film as a prototype, the addition amount of Er in the SiO ₂ —Ta ₂ O ₅ glass film is within the range of several hundred ppm to 2%. It could be changed by adjusting the current value of the electron gun 5. Moreover, the propagation loss of these glass membrane is less than 0.15 dB / cm, the loss in the case of using GeO ₂ or P ₂ O ₅ in place of the conventional Ta ₂ O ₅ (0.25~0.3dB / cm ), A low loss value was realized.

In the present embodiment, Ta ₂ O ₅ was selected as the refractive index control additive because the melting point of SiO ₂ is almost the same as that of SiO ₂ and thus the integrated tablet 3a is irradiated with an electron beam from the electron gun 5. In that case, SiO ₂ and Ta ₂ O ₅ are melted substantially uniformly and vaporized at almost the same evaporation rate.
This is because the refractive index controllability is extremely good. Therefore, a linear proportional relationship can be obtained between the weight percentage of SiO ₂ and Ta ₂ O ₅ and the refractive index, which are predetermined in the powder state. Also, SiO
_Since the powders of ₂ and Ta ₂ O _{5 have} a small particle size of 1 μm or less and the particle sizes are well aligned, the fine particle size of the glass film formed on the substrates 8a to 8n becomes almost uniform to 1 μm or less, This is because a core glass film with low scattering loss can be obtained. Furthermore, since the particle diameters of the SiO ₂ and Ta ₂ O ₅ powders are well aligned, tablets with a sintered density of 90% or more can be made with good reproducibility, which is also a core glass film with low scattering loss. It was effective for realization.

The tablets 3a and 4a of this embodiment were formed with a glass film thickness of 7 .mu.m to 10 .mu.m by using several to ten or more cylindrical tablets having a diameter of 18 mm and a thickness of 10 mm. However, the shape of the tablet may be a quadrangle or a polygon, and the size is not limited to the above value. In addition, the substrates 8a to 8n have a diameter of 3
Although 20 quartz substrates each having a thickness of 1 mm and a thickness of 1 mm were attached to the substrate holder 7, the present invention is not limited to this, like the tablet. For example, the size may be 4 inches or 5 inches, and the material is quartz. In addition to the substrate, a SiO ₂ film on the surface,
Alternatively, it may be a Si substrate having a film containing at least one kind of refractive index controlling additive such as P, B and F in SiO ₂ , and the shape, material and quantity thereof are not limited to those in the above embodiment. Further, if the substrate holder 7 is configured to rotate in the circumferential direction during the glass film formation, it is possible to suppress the deviation of the film thickness and the refractive index within the substrate surface and between the substrates to be small. As an experimental example, it was possible to obtain a refractive index deviation of 0.1% or less in the substrate plane and 0.5% or less between the substrates. Further, the deviation of the film thickness was 0.3% or less within the substrate surface and 3% or less between the substrates. Furthermore, if a film thickness monitor is provided in the apparatus 1, it becomes possible to monitor the film thickness during the formation of the glass film, and the manufacturing yield is improved as compared with the conventional method.

Next, a method for manufacturing a rare earth element-doped optical waveguide using the glass film obtained by the above method will be described.

FIG. 2 shows an embodiment of the rare earth element-doped glass waveguide 15 of the present invention. First, the glass waveguide 15a shown in FIG. 2A is made of Si containing at least one rare earth element obtained on the substrate 8 by the method described above.
A glass film made of O ₂ and Ta ₂ O ₅ is processed into a substantially rectangular shape by photolithography and dry etching to form a core glass 13, and a clad glass layer having a refractive index lower than that is formed on the core glass 13. 2 is formed by forming the buffer layer 16 on the substrate 8 and the core glass 13 obtained by the method described above on the upper surface of the buffer layer 16.
And a clad glass layer 14 are formed,
The glass waveguide 15c of FIG. 2C is obtained by coating a clad glass thin film 17 instead of the clad glass layer 14 of the glass waveguide 15b of FIG. 2B. The clad glass layer 14 and the clad glass thin film 17 are formed by a flame deposition method, a chemical vapor deposition method (CVD method), a plasma CVD method, or the like.

In the glass waveguide 15 shown in FIGS. 2A to 2C, after the core glass film is formed on the substrate 8 by the above-described method, for example, WSi is formed on the core glass film.
A metal film such as a film is formed, and then a photoresist pattern is formed on the metal film by a photolithography process. Next, after masking the photoresist pattern by a dry etching process and peeling the core glass film again by a dry etching process, a glass waveguide is manufactured by coating the entire core glass pattern with a low refractive index film. Become.

As described above, the core glass film is formed by the electron beam evaporation method and is composed of glass composed of SiO ₂ and Ta ₂ O ₅ containing a rare earth element, so that it is a low loss glass. A waveguide is realized. In addition, as described above, the clad glass layers 14 and 17
Is a glass having a refractive index lower than that of the core glass 13, and SiO ₂ or SiO ₂ has P,
It is composed of at least one refractive index controlling additive such as B, F, Ge and Ti.

[0028]

In summary, according to the present invention, the glass film for core is formed by using the electron beam evaporation method. Therefore, by controlling the current value of the electron beam, the glass film for core can be formed. It becomes easy to uniformly add the rare earth element or control the addition amount. Moreover, it becomes easy to control the film thickness and the refractive index of the formed glass. Further, unlike the conventional case, since liquid is not used, there is an excellent effect that a loss is reduced and a light scattering loss is reduced without mixing impurities, and a glass film having high gain can be provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an electron beam vapor deposition apparatus and a manufacturing method used in the first invention.

FIG. 2 is a schematic view showing an embodiment of the present invention.

FIG. 3 is a schematic view showing a method for manufacturing a conventional rare earth element glass waveguide.

[Explanation of symbols]

1 Electron Beam Evaporation Method 3a Tablet made of SiO ₂ and Ta ₂ O ₅ 4a Tablet containing rare earth element 8 Substrate 13 Core glass 14 Low refractive index layer 15 Glass waveguide

Claims (4)

[Claims] 1. A core glass made of SiO ₂ and Ta ₂ O ₅ containing at least one rare earth element is formed on the surface of a substrate, and the core glass is covered with a low refractive index layer such as a clad glass. A rare earth element-doped glass waveguide. 2. S containing at least one of the rare earth elements
The rare earth element-doped glass waveguide according to claim 1, wherein the core glass composed of iO ₂ and Ta ₂ O ₅ is formed by an electron beam evaporation method. 3. A tablet having SiO ₂ and Ta ₂ O ₅ and a tablet containing at least one rare earth element are simultaneously evaporated by an electron beam vapor deposition method on a substrate having a low refractive index layer to obtain at least one rare earth element. Seed-containing SiO
_{A 2-} Ta ₂ O ₅ glass film is formed, and the SiO ₂ —Ta ₂ O ₅ glass film containing at least one of the rare earth elements is processed into a substantially rectangular shape by photolithography and dry etching. A method for manufacturing a rare earth element-doped glass waveguide, characterized in that the entire surface of a substantially rectangular glass film is covered with a low refractive index layer. Integrated tablet wherein said SiO ₂ and Ta ₂ O _5, after uniformly mixed powder of SiO ₂ and Ta ₂ O _5, characterized in that it was formed was solidified in a predetermined shape by hot pressing The method for producing a rare earth element-doped glass waveguide according to claim 3.