JPH05224057A - Production of rare-earth element-added glass film and glass waveguide - Google Patents

Abstract

PURPOSE:To produce a rare-earth element-added glass film with the thickness and refractive index controlled, to which a large amt. of the rare-earth element is uniformly added and capable of making a high gain and to produce a glass waveguide using the film. CONSTITUTION:Substrates 7a, 7b and 7c and three vapor-deposition sources 3, 4 and 5 are provided in the electron-beam vapor deposition device 1, a tablet 3a of SiO2 is placed in the first source 3, a tablet 4a contg. at least two kinds of refractive index controlling additives in the second source 4 and a tablet 5a contg. at least one kind of rare-earth element in the third source 5, then the tablets 3a, 4a and 5a are irradiated with an electron beam and vaporized, and the vapors are deposited on the substrates 7a, 7b and 7c to form an SiO2 glass film contg. the rare-earth element and at least three kinds of the additives.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass film containing at least three kinds of rare earth elements and refractive index controlling dopants, and a method of manufacturing a glass waveguide using the glass film.

[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 It is an object of the present invention to provide a method for producing a rare earth element-added glass film which is obtained by adding a large amount of the rare earth element and has a high gain, and a method for producing a glass waveguide using the same.

[0010]

In order to achieve the above object, a first aspect of the present invention is to provide a substrate and three vapor deposition sources in a chamber of an electron beam vapor deposition apparatus, and use Si as a first vaporization source.
After placing O ₂ tablets, a second evaporation source containing at least two refractive index controlling additives, and a third evaporation source containing at least one rare earth element, Each tablet is irradiated with an electron beam to vaporize the tablet, and the vapor is deposited on the surface of the substrate to form a SiO ₂ glass film containing at least three kinds of rare earth elements and refractive index controlling additives. The second invention is that the tablet to be placed in the second evaporation source is made of a material having a melting point difference of at least two kinds of refractive index control additives within ± 200 ° C. In the invention, the refractive index and the rare earth element concentration are changed in the thickness direction by adjusting the current value of each electron beam and the vapor deposition time. In a fourth aspect of the present invention, the electron beam vapor deposition apparatus is provided with a substrate having a low refractive index layer and three vapor deposition sources, and the first vapor source is SiO 2.
₂ tablets, the second evaporation source contains a tablet containing at least two kinds of refractive index control additives, and the third evaporation source contains a tablet containing at least one rare earth element. The tablet is evaporated by irradiating each with an electron beam, and the vapor is evaporated on the surface of the substrate to form a SiO ₂ glass film containing at least three kinds of rare earth elements and refractive index controlling additives.
The O ₂ glass film is processed into a substantially rectangular shape by photolithography and dry etching, and the entire processed film is covered with a glass film having a low refractive index.

[0011]

As described above, the glass film manufacturing method of the present invention uses the electron beam vapor deposition apparatus having three evaporation sources,
A tablet containing SiO _{2 in} the first evaporation source, a tablet containing at least two kinds of refractive index controlling additives in the second evaporation source, and a tablet containing at least one rare earth element in the third evaporation source. And a glass film is formed on the substrate arranged in the upper part of the electron beam vapor deposition apparatus by adjusting the current value of each electron beam and the vapor deposition time. And Si containing at least two kinds of refractive index control additives
An O ₂ film 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. Further, the tablet put in the second evaporation source is made of a material having a difference in melting point of at least two kinds of refractive index control additives within ± 200 ° C. to eliminate the difference in evaporation rate and suppress cluster generation. A transparent glass film having a particle size of 1 μm or less and a small light scattering loss can be obtained. 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 used for producing the rare earth element-added glass film of the present invention.

As shown in the figure, three evaporation sources 3, 4, 5 formed in a vessel shape are arranged in parallel at the bottom of the chamber 2. Then, a block-shaped tablet 3a obtained by hardening SiO ₂ powder by hot pressing is placed in the first evaporation source 3, and Ge is placed in the second evaporation source 4.
O ₂ (melting point 1100 ° C.) and Ta ₂ O ₅ (melting point 1470
C.) powder is mixed so as to have a desired weight%, and a block-shaped tablet 4a which is hardened by hot pressing is put therein. Furthermore, the third evaporation source 5 further contains at least one rare earth element. A tablet 5a obtained by solidifying Er ₂ O ₃ as a block is put therein. It should be noted that it is better to use powders of various materials used for realizing the above-mentioned tablets, which have a small particle size of 1 μm or less. This is an effective means for significantly reducing the generation or inclusion of clusters that become scattering centers in the film. The tablet 4a contained in the second evaporation source 4 is an additive for controlling the refractive index, and is composed of a mixture of at least two kinds of oxides having a melting point difference close to each other within ± 200 ° C. And the evaporation rate is approaching.
Further, electron beam irradiation units 3b, 4b, 5b are provided near these three evaporation sources 3, 4, 5 and tablets 3a, 4a, which are placed in the evaporation sources 3, 4, 5,
Each of 5a is irradiated with an electron beam so that it is radially evaporated above the tablet 2 as shown in the drawing. Further, the electron beams emitted from these electron beam irradiators 3b, 4b, 5b can be arbitrarily changed by controlling the current value, and by changing the irradiation amount, each tablet can be changed. 3a, 4
The evaporation amounts of a and 5a can be controlled arbitrarily.

A substrate holding dome 6 is provided above the three evaporation sources 3, 4 and 5, and the substrate holding dome 6 has three substrates 7a, 7b and 7b.
c is attached. Further, a heater 8 is provided in the vicinity of the substrate holding dome 6, and the three attached substrates 7a, 7b, 7c are placed at 100 to 400 ° C.
The heating is within the range. Further, a film thickness monitor glass 9 and a photodetector 10 are attached to the chamber 2 above the substrate holding dome 6, and the film is emitted from a film thickness monitor light source 11 provided in the lower portion of the chamber 2 and The film thickness during film formation is monitored by the light passing through the inside.

Further, an oxygen gas introduction system 12 and a vacuum exhaust system 13 are connected to both sides of the chamber 2, and the inside of the chamber 2 is (10 ⁻⁷ T) by the vacuum exhaust system 13.
After evacuation to an (orr) state, oxygen gas is introduced from the oxygen gas introduction system 12 and the oxygen flow rate is adjusted so that the degree of vacuum is 5 × 10 ⁻⁴ to 5 × 10 ⁻⁵ Torr. ..

Next, the manufacturing method of the present invention will be described.

In the above-mentioned state, the tablets 3a, 4a, 5a in the evaporation sources 3, 4, 5 are
When the electron beams from the respective electron beam irradiators 3b, 4b and 5b are irradiated substantially at the same time, as shown in the figure, the respective tablets 3a, 4a and 5a are evaporated radially,
The SiO ₂ —GeO ₂ —Ta ₂ O ₅ glass film containing Er is deposited on the surfaces of the substrates 7a, 7b, 7c located in the upper portion of the chamber 2 while being mixed in the chamber 2 while being mixed. ..

GeO _{2 is} added to SiO _{2 of} this glass film.
The amounts of addition of —Ta ₂ O ₅ and Er ₂ O ₃ can be easily controlled by adjusting the current values of the electron beams with which the evaporation sources 3, 4, and 5 are irradiated. For example, if the current value of the electron beam from the electron beam irradiation unit 3b is 70 m
The current value of each electron beam from the other electron beam irradiation units 4b and 5b is fixed to A and is set to 35 to 50 mA and 4
As a result of changing the glass film within the range of _{5 to} 55 mA, GeO ₂ —Ta ₂ O ₅ and Er ₂ O in SiO ₂ were formed.
The addition amount of ₃ is several mol% to several tens mol% and 100 pp
It could be varied over a range of m to 1%. Moreover,
This glass film is formed with a grain size of 1 μm or less, and has a conventional dual evaporation source method (that is, SiO ₂ —GeO ₂ —T).
a ₂ O ₅ tablet)
It was possible to obtain a glass film having a small light scattering loss without clusters having the above grain size. Further, as described above, the refractive index controlling additive of the tablet 4a is composed of a mixture of at least two kinds of oxides whose melting points are close to each other within ± 200 ° C., and their evaporation rates are also close to each other. However, the reason is that when the difference in melting point of at least two kinds of refractive index control additives is ± 200 ° C. or more, clusters having a particle size of several μm or more are generated in the formed glass film, This is because the light scattering loss increases. The film thickness during film formation is monitored by the film thickness monitor glass 9, the photodetector 10 and the film thickness monitor light source 11 provided in the chamber 2.

The above-mentioned G is used as the refractive index controlling additive.
In addition to eO ₂ and Ta ₂ O ₅ , TiO ₂ (melting point 1820
℃), ZnO (melting point 1725 ℃), Al ₂ O ₃ (melting point 2
045 ° C), Cr ₂ O ₃ (melting point 2435 ° C), MgF ₂
(Melting point 1260 ° C.), CeF ₃ (melting point 1320 ° C.), M
gO (melting point 2850 ° C), ZrO ₂ (melting point 2700 ° C)
Nb ₂ O ₅ (melting point 1520 ° C.) and the like can be used in combination. Er ₂ O is used as a rare earth element.
₃ (melting point 2390 ° C.), CeO ₂ (melting point 1950
℃), Eu ₂ O ₃ (melting point 2100 ℃), La ₂ O ₃ (melting point 2315 ℃), Sm ₂ O ₃ (melting point 2325 ℃), Nd
₂ O ₃ (melting point 1520 ° C.) or the like can be used.

Next, a method of 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 a method for manufacturing a rare earth element-doped optical waveguide of the present invention. First, Figure 2
As shown in (a), the core layer 16 (refractive index nw, nw> nb) is formed on the substrate 15 having the low refractive index layer 14 (refractive index nb) obtained by the above-mentioned method, and A metal film 17 (for example, a WSi film) is formed on the core layer 16 by a sputtering method, a vacuum deposition method, an ion plating method, or the like. This metal film 17 has a thickness Tμ.
m (T: in the range of several μm to several tens of μm), the thickness is sufficient to etch the core layer 16 (0.1 μm to 1 μm).
m).

Next, as shown in FIG. 2B, a photoresist film pattern 18 is formed on the metal film 17 as a mask for etching the metal film 17 by photolithography. Thereafter, as shown in FIG. 2C, the metal film 17 is etched by dry etching using the photoresist film pattern 18 as a mask. This dry etching is performed in a plasma atmosphere using a reactive ion etching apparatus while flowing NF ₃ gas. Next, as shown in FIG. 2D, the metal layer 17 is masked and the core layer 16 is dry-etched.
Also in this dry etching, a reactive ion etching apparatus is used and etching is performed in a plasma atmosphere while flowing a CHF ₃ gas. Then, as shown in FIG. 2E, the metal film 17 is peeled off. This peeling is performed by dry etching using the NF ₃ gas. And finally Figure 2 (f)
As shown in FIG. 5, a clad layer 19 having a refractive index of nc (nc <nw) is coated on the surface of the etched core pattern.
The cladding layer 19 is formed by flame deposition method, plasma CV
It is realized by the D method, the low pressure CVD method or the like.

[0024]

In summary, the present invention has the following excellent effects.

[0025] (1) making a tablet for refractive index control additive to be added to the SiO ₂ in the rare earth element and SiO ₂ of independently evaporation these tablets independently by the electron beam respectively placed in separate evaporation Gennai Therefore, it is possible to easily control the refractive index and the concentration of the rare earth element added.

(2) Further, the glass film formed has a particle size of 1
The film is transparent and has a small light scattering loss of μm or less.

(3) As a result, it is possible to obtain a rare earth element-added glass film with low loss and high gain characteristics.

[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 fourth 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 Vapor Deposition Device 2 Chamber 3, 4, 5 Vapor Deposition Source 3a, 4a, 5a Tablet 7a, 7b, 7c Substrate

Front page continuation (72) Inventor Katsuyuki Imoto 3550 Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Cable Ltd. Advanced Research Center (72) Inventor Seiichi Kashimura 3550 Kida-yocho, Tsuchiura City, Ibaraki Hitachi Cable Advanced Research Co., Ltd. In the center

Claims (4)

[Claims] 1. A substrate and three vapor deposition sources are provided in a chamber of an electron beam vapor deposition apparatus, and Si is used as a first vaporization source.
After placing O ₂ tablets, a second evaporation source containing at least two refractive index controlling additives, and a third evaporation source containing at least one rare earth element, Each of the tablets is irradiated with an electron beam to vaporize the tablet, and the vapor is deposited on the surface of the substrate to form a SiO ₂ glass film containing at least three kinds of rare earth elements and refractive index controlling additives. A method for producing a glass film containing a rare earth element. 2. The tablet placed in the second evaporation source is made of a material having a difference in melting point of at least two kinds of refractive index controlling additives within ± 200 ° C. A method for manufacturing a glass film containing a rare earth element. 3. The rare earth element addition according to claim 1, wherein the refractive index and the rare earth element concentration are changed in the thickness direction of the SiO ₂ glass film by adjusting the current value of each electron beam and the vapor deposition time. Method for manufacturing glass film. 4. A chamber having an electron beam vapor deposition apparatus is provided with a substrate having a low refractive index layer and three vapor deposition sources, and
A tablet containing SiO _{2 in} the first evaporation source, a tablet containing at least two kinds of refractive index controlling additives in the second evaporation source, and a tablet containing at least one rare earth element in the third evaporation source. After the addition, the tablets are each irradiated with an electron beam to evaporate the tablets, and the steam is deposited on the surface of the substrate to form a SiO ₂ glass film containing at least three kinds of rare earth elements and refractive index controlling additives. And processing the SiO ₂ glass film into a substantially rectangular shape by photolithography and dry etching, and covering the processed film with a glass film having a low refractive index. Production method.