JP3085559B2 - Method of manufacturing rare earth ion-containing glass waveguide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Attention has been paid to research and development for realizing lasers and optical amplifiers by adding rare earth ions into the core of a glass waveguide.

FIG. 7 shows a conventional example of a method of adding rare earth ions into a core of a glass waveguide. That is, a glass porous film for a core portion on a substrate obtained in a step of forming a glass optical waveguide film having a core portion through which light propagates and a cladding layer around the core portion on the substrate is made of a rare earth element and a transition metal. Immersion in a solution containing at least one element selected from the elements, adding the element to the core at a predetermined concentration, drying and sintering, and then performing photolithography and dry etching to form a clad on the surface of the core. This is a method of obtaining a rare earth ion-doped glass waveguide for a laser or an optical amplifier by depositing a layer. (JP-A-2-2508
No. 3)

[0004]

However, it is difficult for the above-mentioned conventional method for manufacturing a rare earth ion-doped glass waveguide to realize the following.

[0005] It is difficult to uniformly add rare earth ions into the core. This is because the above-mentioned conventional method is a method of impregnating a liquid into a glass porous film and then forming a transparent glass by a drying and sintering process. The concentration gradient of rare earth ions causes a decrease in excitation efficiency.

[0006] It is difficult to add a large amount of rare earth ions into the core.

[0007] Since it is a method of depositing a glass porous film and then sintering it to form a transparent glass, it is difficult to control the film thickness and the refractive index.

[0008] When impregnating a liquid into a porous glass membrane, impurities are easily mixed therein, and it is difficult to reduce the loss.

The present invention has been devised in order to effectively solve the above-mentioned problems, and an object of the present invention is to uniformly add rare earth ions to a core glass film and to easily control the amount of addition. It is another object of the present invention to provide a method for manufacturing a rare-earth-ion-containing glass waveguide, which can control the refractive index and the film thickness thereof easily.

[0010]

According to a first aspect of the present invention, a substrate heated to a desired temperature is disposed in an upper portion of a chamber during evacuation, and a lower portion of the substrate is disposed in a lower portion of the substrate.
a first evaporator for evaporating an iO ₂ -based tablet by electron beam irradiation, a second evaporator for evaporating a refractive index controlling additive tablet by an electron beam or a heat source, and a tablet of an organometallic compound containing a rare earth element And a vaporizing unit for vaporizing the same by a heat source.The first evaporating unit, the second evaporating unit, and the vaporizing unit evaporate an SiO ₂ system, a refractive index control additive, and an organometallic compound containing a rare earth element, respectively. A SiO ₂ -based film containing the refractive index control additive and rare earth ions is formed on a substrate, and the second invention changes the amount of vaporization of the organometallic compound containing the rare earth element, It controls the content of rare earth ions in the SiO ₂ -based film to be formed, and the third invention is to change the evaporation amount of the refractive index control additive,
This is for controlling the content of the refractive index controlling additive in the formed SiO ₂ -based film. Further, the fourth invention is to form a film while introducing an oxidizing gas from the outside into the chamber, and the fifth invention contains a refractive index control additive and rare earth ions on the substrate. after forming the SiO ₂ based film, to the SiO ₂ based layer surface, is subsequently are those forming this evaporating the SiO ₂ system only the first evaporation portion, further sixth invention, the before the deposition of the SiO ₂ based film containing additives and a rare earth ion for refractive index control on the substrate, is intended for forming this evaporating the SiO ₂ system only advance the first evaporation unit.

[0011]

According to the first aspect of the present invention, the evaporation of the SiO ₂ system and the additive for controlling the refractive index and the vaporization of the organometallic compound containing a rare earth element are simultaneously performed according to the first aspect of the present invention. Therefore, rare earth ions can be uniformly added to the core glass film to be formed. The content of rare earth ions in the core glass film can be easily controlled by adjusting the amount of the rare earth element vaporized by the organometallic compound. In addition, the rare-earth ions are not physically evaporated, but physically evaporated by employing a chemical vaporization method under a much higher vacuum than conventional chemical vapor deposition. _It is easy to enter into system ₂ and the additive for controlling the refractive index. Further, since the particles enter in a state of ultrafine particles, clusters in the glass film are less likely to occur, and it is possible to suppress a reduction in light amplification phenomenon due to concentration quenching. Furthermore, the amount of evaporation of the SiO ₂ system and the additive for controlling the refractive index can be easily controlled by adjusting the beam current of the electron beam, thereby easily controlling the film thickness and the refractive index. Can be.

According to the second aspect, the content of rare earth ions can be easily controlled during the formation of the film, so that the excitation efficiency can be improved by intensively containing the rare earth ions only in the central portion of the film. Can be improved. Further, a new optical device having a quantum well structure can be realized by forming a layer having a high content of rare earth ions and a layer having a low content of rare earth ions in a multilayer shape in the film thickness direction.

According to the third aspect, the content of the refractive index controlling additive can be easily controlled during the formation of the film. For example, by increasing the refractive index near the center of the film, The optical confinement efficiency is improved, and as a result, a high gain optical amplifier can be obtained. In addition, by forming a refractive index distribution of a so-called W-type structure in which layers having a low refractive index are provided above and below the film, light confinement and a reduction in scattering loss due to non-uniform structure above and below the film can be expected. it can.

According to the fourth aspect, since the oxygen partial pressure during film formation can be adjusted, it is possible to reduce stress in the film, peel off the film, and generate cracks in the film. Thereby, a hot glass film of 10 μm or more can be formed on the substrate.

According to the fifth invention, after forming an SiO ₂ -based film (first layer film) containing a refractive index control additive and rare earth ions on a substrate, a high vacuum clean is formed on the film surface. SiO ₂ based film (second layer film) while keeping the atmosphere
Is formed to protect the SiO ₂ -based film containing the above-described additive for controlling the refractive index and rare earth ions, so that the light propagation loss due to the contamination of the surface of the first layer film and the patterning accuracy due to photolithography and dry etching decrease. Can be prevented. Further, since the second layer film can be used as the clad film, an optical waveguide having a uniform interface between the core film of the first layer film and the clad film can be realized.

According to the sixth aspect of the present invention, before the first layer film is formed on the substrate, the SiO ₂ -based film is formed in advance, thereby reducing the scattering loss caused by the non-uniformity of the substrate surface. be able to. In addition, a high-loss, low-cost substrate can be used, and cost reduction can be achieved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 evaporation apparatus according to the present invention. As shown in the figure, a substrate holding dome 2 is provided in the upper portion of the evacuated chamber 1, and a plurality of substrates 3 are attached to the dome 2, for example, so that one surface thereof faces downward. The substrate 3 is heated to a temperature in the range of 100 to 650 ° C. by a heater 4 provided near the substrate holding dome 2. A first evaporator 5 and a second evaporator 6 are provided below the dome 2 for holding a substrate, and a vaporizer 7 is provided between the first evaporator 5 and the second evaporator 6. Is provided.

The first evaporating section 5 includes a SiO ₂ tablet 8 and an electron beam irradiating section 9. The electron beam irradiating section 9 irradiates the SiO ₂ tablet 8 with an electron beam B to emit the SiO ₂ tablet 8. Is evaporated, and the substrate 3
It is designed to be deposited on top. The SiO ₂ tablet 8 is obtained by solidifying a powder containing SiO ₂ as a main component by hot pressing to form a block.
TiO ₂ in O _2, Ta ₂ O ₅ oxide few weight percent, such as
To some extent.

The second evaporating section 6 comprises a refractive index controlling additive tablet 10 and an electron beam irradiating section 9. Like the first evaporating section 5, the electron beam irradiating section 9 controls the refractive index control. The additive additive tablet 10 is irradiated with the electron beam B to evaporate the additive for controlling the refractive index, and the additive is deposited on the substrate 3. The refractive index controlling additive tablet 10 is made of GeO ₂ , Al ₂ O ₃ , P ₂
The powder containing at least one additive for controlling the refractive index, such as O ₅ and Ta ₂ O ₅ , is formed into a block by solidifying the powder by hot pressing, and the amount of evaporation of the tablet 10 is adjusted. The refractive index of the formed glass film is controlled. That is, by adjusting the amount of evaporation during film formation, a refractive index distribution can be provided in the thickness direction.

The vaporizing section 7 contains an organic metal compound containing a rare earth element in an evaporation source 11 such as a boat, a filament, a crucible, a basket, and the like. Is vaporized and added to the SiO ₂ system deposited on the substrate 3. As the organometallic compound containing the rare earth element, a rare earth compound which is solid at normal temperature, for example, R (DPM) ₃ , R (HFA) ₃ , R (F
OD) ₃ , where R: Er, Nd, Sm, Eu, Y
and rare earth elements such as b, Pr, and La.

[0022] A glass film 13 for monitoring the film thickness and a photodetector 14 are mounted on the upper part of the dome 2 for holding the substrate. Is monitored.

A method for forming a SiO ₂ -based film containing the additive for controlling the refractive index and the rare earth ions in the above structure will be described. First, after evacuating the chamber 1 to a high vacuum (about 10 ⁻⁷ Torr), the oxidizing gas G (for example,
O ₂ , N ₂ O, ozone, etc.) are introduced as shown by the arrows, and the flow rate of the oxidizing gas G is adjusted so that the degree of vacuum becomes 5 × 10 ⁻⁴ to 5 × 10 ⁻⁵ Torr. Next, in such a state, a voltage is applied to each of the evaporation units 5 and 6,
The electron beam irradiating section 9 irradiates the SiO ₂ -based tablet 8 and the refractive index controlling additive tablet 10 with the electron beam B to evaporate, and the heater 12 of the vaporizing section 7.
As a result, the organic metal compound containing the rare earth element in the evaporation source 11 is vaporized, and a glass film is formed on the substrate 3 held by the substrate holding dome 2. These evaporators 5, 6 and vaporizer 7 are simultaneously turned on to start evaporation and vaporization. The evaporation amount of the evaporating section 6 is controlled by adjusting the beam current of the electron beam B, whereby the addition amount of the refractive index controlling additive in the film is controlled. That is, the refractive index of the film is changed by the ratio of the respective evaporation rates. If the vaporizing section 7 uses, for example, a filament, the amount of vaporization is controlled by adjusting the filament current, thereby controlling the amount of rare earth ions added to the glass film. still,
The film formation state is film thickness monitor glass 13, photodetector 1.
4. Monitoring can be performed in real time by the light source 15 for film thickness monitoring.

In this method of forming a glass film, the SiO ₂ system and the additive for controlling the refractive index are independently evaporated or vaporized depending on the irradiation amount of the electron beam B, so that the refractive index of the formed glass film can be easily controlled. be able to. Also, the amount of rare earth ions to be added can be easily controlled by changing the filament current, and the film thickness can be easily controlled. In addition, since the glass film is formed under a high vacuum and clean atmosphere, there is no need to worry about an increase in loss due to impurity contamination. Further, since the above-mentioned glass film is a transparent and dense film, a sintering process is not required as in the related art. Even if heat treatment is performed, 1200
Since the temperature is lower than or equal to ° C., diffusion and evaporation of rare earth ions contained in the glass film are extremely small. Further, as described above, the rare earth ions evaporate while being vaporized and are contained in the film, so that they are rarely contained in the film as large granular masses. Therefore, a glass film for an active device with low loss and high excitation efficiency can be realized.

As described above, according to the present invention, the amount of vaporization can be controlled by adjusting the vapor pressure and the temperature, and furthermore, it evaporates in the form of ultrafine particles (several hundreds of mm or less). Can be added. Therefore, it is possible to solve the problem that the excitation efficiency is reduced by being added to the glass film in a cluster state as in the related art.

FIG. 2 shows a modified embodiment of the present invention. As shown in the drawing, in the present embodiment, a first evaporator 5 having a built-in SiO ₂ tablet 8 which is a main component of a glass film is arranged directly below a dome 2 for holding a substrate. A second evaporating unit 6 having a built-in refractive index control tablet 10 for adding a trace amount, and a vaporizing unit 7 having a rare earth element built therein, and other configurations are the same as those of the first embodiment. It is. That is, in the first embodiment, the SiO ₂ based tablet 8 which is a main component of the glass film is provided on the outer periphery of the vaporizing portion 7 provided at the center.
Since the first evaporating section 5 having the built-in structure is located, the distance from each substrate 3 held by the substrate holding dome 2 may be different, resulting in non-uniform film formation. By locating the first evaporator 5 at the center, the distance from each substrate 3 held by the substrate holding dome 2 becomes uniform, and the uniformity of the SiO ₂ -based film is improved.

FIGS. 3 to 6 show various embodiments of the substrate with a glass film realized by the method of the present invention. First, a substrate with a glass film shown in FIG. 3 has a refractive index control additive and SiO ₂ containing rare earth ions on a substrate 3.
The substrate 3 is made of glass (quartz, borosilicate, Vycor, etc.), semiconductor (S
i, GaAs, InP, etc.), a magnetic material, or the like. The substrate with a glass film shown in FIG. 4 is obtained by continuously forming a second layer film 17 on the first layer film 16 of FIG. 3, and this second layer film 17 is a SiO ₂ -based film. . Also,
In the substrate with a glass film shown in FIG. 5, before forming the first layer film 16 on the substrate 3, the low refractive index layer film 18 (ie, Si
O ₂ based film) is obtained by the formation, further, continuously forming the low refractive index layer film 18, the first layer film 16 and the second layer film 17 substrate with the glass films on the substrate 3 shown in FIG. 6 It was done.

In each of the substrates with a glass film shown in FIGS. 3 to 6, the refractive index distribution in the first layer film 16 may be uniform or the refractive index near the center of the film thickness may be increased to increase the light intensity. May be better confined. Also, the content of rare earth ions in the first layer film 16 is increased as in the above-described refractive index distribution by increasing the content near the center and decreasing the content toward the periphery to increase the excitation efficiency. You may. Further, it is also possible to configure a wavelength-selective optical amplifier by adopting a structure in which thin layers having a high rare earth ion content and thin layers having a low rare earth ion content are alternately stacked.

Next, a specific embodiment using the apparatus shown in FIG. 2 will be described.

Twelve disk-shaped (diameter: 20 mmφ, thickness: 15 mmt) SiO ₂ powders having a particle size of 1 μm or less are hot-pressed on the SiO ₂ tablet 8 of the first evaporator 5. GeO _{2 having a} particle size of 1 μm or less is added to the refractive index controlling additive tablet 10 of the second evaporating section 6.
Six pieces prepared in the same disk shape as above by hot pressing using powder were placed. In addition, one Er (DPM) ₃ block (diameter 8 mmφ, thickness 12 mmt) was installed in the evaporation source 11 containing the rare earth element in the vaporization section 7. After evacuating the chamber 1 to a high vacuum of about 10 ⁻⁷ Torr, O ₂ gas was introduced into the chamber 1 and the degree of vacuum was maintained at 5 × 10 ⁻⁵ Torr. 10 was irradiated with the electron beam B, and at the same time, a current was supplied to the evaporation source 11 to perform vapor deposition. Where SiO ₂
The deposition rate of Ge is in the range of 5.3 to 6.8 ° / sec.
O ₂ is in the range of 0.1 to 0.8 ° / sec.
Could be controlled in the range of 3 × 10 ⁻³ to 4 × 10 ⁻² Å / sec. The resulting film has a particle size of 1 μm as compared with the physical vapor deposition method using a conventional electron beam vapor deposition method.
These clusters were hardly observed. That is,
This is considered to be due to the effect of chemically evaporating Er under an extremely high vacuum. In addition, SiO ₂ and GeO with different melting points
It is also believed that the independent evaporation of ₂ contributes additionally.

As described above, the present invention relates to the method shown in FIG.
By using a new manufacturing method that combines physical vapor deposition and chemical vapor deposition under a much higher vacuum than conventional gas-phase chemical vapor deposition (CVD), a film with extremely small particle size and uniformity can be obtained. It is possible to form a film with high purity, and it is possible to make rare-earth ions more uniform and ultrafine compared to the method in which the SiO ₂ system, the additive for controlling the refractive index, and the rare earth element are all physically evaporated by electron beam evaporation. It can be added in a state.

The present invention is not limited to the above embodiment. First, in FIGS. 1 and 2, the second evaporation source may be a resistance heating system using a filament, a boat, etc., in addition to the electron beam. . That is, the additive for controlling the refractive index is S
Since the melting point is lower than that of the iO ₂ system, a tablet, chip or powdery additive for controlling the refractive index is placed in a filament, boat, or the like, and the filament (or boat) is added.
It is also conceivable to evaporate the above additive by passing a current through it.

[0033]

As described above, according to the method of the present invention, rare earth ions can be uniformly added to the core glass film of the optical waveguide, and the amount thereof can be easily controlled.
Further, the refractive index and the thickness of the core glass film can be easily controlled. Further, since a film can be continuously formed under a high vacuum, there is an excellent effect that there is almost no increase in light loss due to mixing of impurities.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of an electron beam evaporation apparatus according to the present invention.

FIG. 2 is a schematic view showing another embodiment of the electron beam evaporation apparatus according to the present invention.

FIG. 3 is a cross-sectional view showing one embodiment of a substrate with a glass film realized by the method of the present invention.

FIG. 4 is a sectional view showing a second embodiment of the substrate with a glass film realized by the method of the present invention.

FIG. 5 is a sectional view showing a third embodiment of a substrate with a glass film realized by the method of the present invention.

FIG. 6 is a sectional view showing a fourth embodiment of a substrate with a glass film realized by the method of the present invention.

FIG. 7 is a process chart showing a conventional method of adding rare earth ions into a core of a glass waveguide.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 3 Substrate 5 First evaporator 6 Second evaporator 7 Vaporizer

──────────────────────────────────────────────────の Continuing from the front page (72) Katsuyuki Imoto, 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Inside the Hitachi Research Center, Inc. (72) Seiichi Kashimura 3550 Kida Yomachi, Tsuchiura City, Ibaraki Hitachi, Ltd. (56) References JP-A-4-22906 (JP, A) JP-A-3-53202 (JP, A) JP-A-5-224057 (JP, A) JP-A-5-205 294653 (JP, A) JP-A-3-35203 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/12-6/14 H01S 3/06

Claims (6)

(57) [Claims] 1. A substrate heated to a desired temperature is arranged above a chamber under vacuum evacuation, and S
a first evaporator for evaporating an iO ₂ -based tablet by electron beam irradiation, a second evaporator for evaporating a refractive index controlling additive tablet by an electron beam or a heat source, and a tablet of an organometallic compound containing a rare earth element And a vaporizing unit for vaporizing the same by a heat source.The first evaporating unit, the second evaporating unit, and the vaporizing unit evaporate an SiO ₂ system, a refractive index control additive, and an organometallic compound containing a rare earth element, respectively. A method of manufacturing a rare earth ion-containing glass waveguide, comprising forming a SiO ₂ -based film containing the refractive index control additive and rare earth ions on a substrate. 2. The method according to claim 1, wherein the content of rare earth ions in the formed SiO ₂ -based film is controlled by changing the amount of vaporization of the organometallic compound containing the rare earth element. A method for manufacturing a rare earth ion-containing glass waveguide. 3. The content of the refractive index controlling additive in the formed SiO ₂ based film is controlled by changing the evaporation amount of the refractive index controlling additive. Or 2
The manufacturing method of the rare-earth-ion containing glass waveguide as described in the above. 4. A film is formed while introducing an oxidizing gas from the outside into the chamber.
The manufacturing method of any one of the rare earth ion-containing glass waveguides. 5. An SiO ₂ -based film containing an additive for controlling a refractive index and a rare earth ion is formed on the substrate.
_{On the} surface of the O ₂ -based film, Si
Claim 1 or the method of producing the rare-earth ion-containing glass waveguide according to, characterized in that the O ₂ system is evaporated to deposit it. 6. A before forming the SiO ₂ based film containing additives and a rare earth ion for refractive index control on the substrate, forming this by only advance the first evaporator unit to evaporate the SiO ₂ system The method for producing a rare earth ion-containing glass waveguide according to any one of claims 1 to 5, wherein the glass waveguide is formed as a film.