KR20010047298A - Planar optic amplifier using aerosol process and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A planar optical amplifier using an aerosol process and a method for manufacturing the same are to dope plenty of erbium into the optical amplifier without a clustering phenomenon by utilizing the aerosol process, thereby reducing a length of the amplifier and a manufacturing cost. CONSTITUTION: A planar optical amplifier includes a silicon substrate(10), an underclad(20), a core(30) which is formed by an aerosol process, and an overclad(40) formed by using the aerosol process. In a method for manufacturing a planar optical amplifier, an underclad is formed on a silicon substrate. A core layer is formed using an aerosol process. The core layer is patterned into a predetermined configuration, thereby forming a core. An overclad is formed using the aerosol process. In the manufacturing step of the core layer, a sol solution is prepared in advance. An aerosol is formed using the sol solution and is deposited on the underclad. An annealing process is carried out for melting the deposited aerosol. A glass film is formed by cooling the melted aerosol.

Description

Planar optical amplifier using aerosol process and manufacturing method thereof {PLANAR OPTIC AMPLIFIER USING AEROSOL PROCESS AND METHOD FOR MANUFACTURING THE SAME}

An object of the present invention is to provide a flat panel optical amplification device manufactured using an aerosol process and a method for manufacturing the same as an element used in optical communication.

Although optical signal transmission paths are mostly used in optical communication, it is technically limited to fabricate high-performance devices having multiple channels such as multi-branch optical couplers and WDM (wavelength division multiplex) devices. Therefore, the technology of integrating the optical fiber uses a technique for implementing a path of an optical signal on a planar substrate, called a Planar Lightwave Circuit (PLC). Flat panel optical devices manufactured by PLC technology can be made of various materials such as semiconductors, silica, and polymers, but silica is composed of a material similar to optical fiber, which has low transmission loss and low connection loss with optical fiber. Since it can be processed using semiconductor processing techniques such as photolithography and etching, it is widely used as a material for flat panel optical devices. The present invention provides a plate-type optical amplification device using silicon as a substrate and a silica thin film layer of an underclad, a core, an overclad, etc. deposited on the substrate by an aerosol process, and a method of manufacturing the same. It is about.

As a method of forming a silica thin film on a substrate, FHD (Flame Hydrolysis Deposition), CVD (Chemical Vapor Deposition), sol-gel (Sol-gel), powder process method and the like are used. The dual FHD method has a high deposition rate and easy formation of a thick film than a CVD method, and thus has the advantage of making a high purity silica waveguide similar to the size of an optical fiber cross section. In the FHD method, oxides such as B, P, and Ge are added as dopants for controlling the refractive index, heat treatment temperature, and the like of the silica optical waveguide film. Conventional techniques for producing optical waveguides using the FHD method are disclosed in EP 0 545 432 and 0 751 408 and the like.

However, the FHD process uses a high vapor pressure chloride material, which presents a high risk, high flame temperatures used to deposit the waveguide (above 1500 ^o C), making it difficult to add large amounts of dopants and controlling the dopant content. There is a difficult problem. For this reason, it is difficult to control the refractive index and the heat treatment temperature of each layer when making the under clad, core and over clad layers using the FHD method. In particular, when the over cladding layer is formed using the FHD method, it is difficult to control the heat treatment temperature to 1100 ^° C. or less due to the limitation of material selection. However, when the heat treatment temperature of the over cladding layer is high, the over cladding layer This can affect the shape of the underlying core and cause serious problems in optical signal processing.

In addition, the FHD method has a problem in that it is difficult to add alkali, alkaline earth, and other rare earth metals having low vapor pressure to the optical waveguide layer in order to manufacture the optical amplifier.

At present, the light source for optical communication uses wavelengths of 1.3 μm and 1.5 μm, and the wavelength of 1.5 μm is the least loss in silica, and the null is used as the communication wavelength. As the optical transmission distance using optical fiber is gradually increased and high functional devices are introduced, the optical transmission method is gradually limited.

Rare earth-doped fiber amplifiers, especially erbium doped fiber amplifiers (EDFAs), are ideal for overcoming fiber loss in the 1.55 µm wavelength range. Therefore, such an amplifier can be used to increase the optical transmission length, and its application range is widened with various optical passive elements. EDFAs are very difficult to fabricate, and with current technology, only a small amount (a few ppm / m) of erbium can be added. When only a small amount of erbium is added, the amplifier length is long (for example, 20 to 50 m at 20 dB gain, based on 200 times amplification of the optical signal), and therefore, the cost (about 30,000 won / m) is also expensive.

Since silica has a covalent bond structure, when a large amount of erbium is added, the erbium ions break the covalent bonds and do not settle, and a clump of erbium ions is formed. This massing phenomenon causes light loss due to light scattering and worsens amplification characteristics. In order to eliminate such masses, when alkali is added to the silica, covalent bonds are broken and the silica structure is opened to the ionic bond structure, whereby erbium ions are easily settled. However, it is known that it is very difficult to add alkali ions and only a very small amount is added by the conventional optical fiber manufacturing method, and it is reported that alkali or erbium ions are not evenly distributed.

Using Planar Lightwave Circuit (PLC) manufacturing technology instead of optical fiber makes it possible to manufacture small and low cost optical amplifiers, and it is possible to integrate active and passive devices on a single substrate. It is possible to implement Accordingly, research has been made on erbium-doped devices in the field of flat panel optical devices. However, the conventional FHD method is limited in the composition of the material as described above, it is very difficult to produce a thin film to which erbium is uniformly added.

Accordingly, it is an object of the present invention to provide a low cost, high performance erbium-doped flat plate optical amplifier.

Another object of the present invention is to provide a method for manufacturing a plate type optical amplification device using an aerosol process.

Another object of the present invention is to provide a flat panel optical amplification device comprising a core and an overclad produced using an aerosol process.

1 is a cross-sectional view showing the structure of an optical amplifying device of the present invention.

Figure 2 is a schematic diagram of the aerosol processing equipment used in the manufacture of the optical amplification device of the present invention.

3 is a graph showing the refractive index and the consolidation temperature of a (92-x) SiO ₂ -xB ₂ O ₃ -8P ₂ O ₅ glass thin film.

4 is a graph showing a change in refractive index of a glass thin film with a change in annealing temperature.

5 is a graph showing the change in refractive index when GeO ₂ is added.

6 is a graph showing the change in refractive index when Er ₂ O ₃ is added.

<Explanation of symbols for the main parts of the drawings>

10: silicon substrate

20: under cladding

30: core

40: overclad

50: holder

60: substrate

70: torch

80: aerosol generator

90: X-Y stage

In order to achieve the above object, a planar optical amplifier manufactured using an aerosol process has been disclosed. The plate type optical amplifying device of the present invention includes a silicon substrate 10, an underclad 20, a core 30 formed using an aerosol process, and an over clad formed using an aerosol process. (overclad, 40).

In addition, a method of manufacturing a flat plate optical amplifying device using an aerosol process has been disclosed. In the method of manufacturing the optical amplification device according to the present invention, the under cladding 20 is formed on the silicon substrate 10, the core layer is formed by using an aerosol process, and the core layer is etched to form the core 30. And forming the overclad 40 by using an aerosol process.

1 shows a flat panel optical amplification device of the present invention manufactured using an aerosol process. Looking at the structure of the optical amplification device of the present invention is composed of a silicon substrate 10, an underclad (20), a core 30 and an overclad (40). An optical amplification device manufacturing process is briefly described as follows. First, the underclad 20 is formed on the silicon substrate 10 by using a known silica thin film manufacturing method. The under cladding 20 may be formed using, for example, an FHD method that is easy to manufacture any thick film using a material such as SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , and can be mass-produced. It doesn't happen.

After the under clad is formed, a core layer, which is a borophosphosilicate-based glass thin film in which alkali and a large amount of erbium is added, is formed on the under clad 20 using an aerosol process. Briefly describing a core layer forming method using an aerosol process is to form a glass thin film by melting the fine particles at a high temperature through a heat treatment process (densification process) after depositing the fine particles on the under clad through the aerosol process. After the core layer is formed, the core layer is etched using the semiconductor process technology to leave only the optical circuit pattern portion (the core 30 portion in FIG. 1). In the present invention, Na ₂ O and a large amount of P ₂ O ₅ or the like is suitably included in the core layer as a dopant so that a large amount of erbium is included in the core layer without lumping.

After the core 30 is formed, the overclad 40 is formed on the under clad 20 and the core 30 using an aerosol process. In the present invention, Na ₂ O was added to the SiO ₂ -B ₂ O ₃ -based glass to lower the melting point when manufacturing the over cladding layer, thereby enabling heat treatment at 1100 degrees or less. As a result, no deformation occurs in the shape of the core even after the overclad heat treatment, and thus an optical device having high reproducibility in manufacturing can be obtained.

The aerosol process used in the present invention is a method in which a liquid sol is formed into particles using an ultrasonic vibrator and oxidized with an acid / hydrogen flame to be deposited on a substrate. The aerosol process has a very limited restriction on the addition of dopants compared to the FHD method, and thus it is possible to freely control the content of B, P, Ge and the like. It was found by experiment that an amorphous clear glass thin film containing 0.1-2 mol of B ₂ O ₃ , 0.1-45 mol of P ₂ O ₅ , and 0.1-20 mol of GeO ₂ was added.

The aerosol process also allows the addition of large amounts of metals, such as alkali metals, which are low vapor pressure and difficult to transport into the gas phase, and rare earths, which are heavy ions. Therefore, even though it is a suitable method for the fabrication of a flat plate type optical amplification element which should contain an element such as erbium with low vapor pressure, many studies have not been made. In addition, the aerosol process has the following advantages.

-It is possible to manufacture multi-component glass thin films with low light transmission loss.

-Fast deposition speed and easy fabrication of thick film of several to several tens of micrometers.

-It is possible to obtain almost the same refractive index with the device of almost the same size as the optical fiber, so the connection loss of the optical fiber is small.

-Economical as it can be mass produced and manufactured at room temperature.

Looking at the aerosol process, that is, the glass thin film manufacturing process using aerosol used in the core 30 and the over cladding 40 in the present invention in detail as follows. First, certain materials (e.g. TEOS (tetraethyl orthosilicate), B [(CH ₃ ) ₂ CHO] ₃ , H ₃ PO ₄ , Ge (OC ₂ H ₅ ) ₄ , Er (NO ₃ ) ₃ .5H ₂ O , HNO ₃ , methanol, distilled water, etc.) to prepare a sol solution. To this end, TEOS is first hydrolyzed in a solvent with a molar ratio of 5: 1 of distilled water and methanol for 1 hour. Nitric acid is used as a hydrolysis catalyst, and when the amount of phosphoric acid is large, the amount of nitric acid is reduced. B [(CH ₃ ) ₂ CHO] ₃ and Ge (OC ₂ H ₅ ) ₄ were slowly added thereto and reacted for 3 hours while stirring with a magnetic stirrer. The composition ratio of this sol solution depends on the composition ratio of the thin film to be produced, and the composition ratio of the preferred sol solution used in the production of each layer of the present invention is shown in Table 1.

Under Clad Solution mol Core solution mol Over clad solution mol SiO ₂ 80 to 85 30-70 20-50 B ₂ O ₃ 5 to 15 5-10 50-80 P ₂ O ₅ 5 to 15 25-65 GeO ₂ + 2-12wt Na ₂ O +0.5 to 5wt +0.5 to 5wt Er ₂ O ₃ + 0.2-5wt

More preferably, the sol solution for making the core is 40-50 mol, approximately 5 mol, 45-55 mol, 2-, of SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , Na ₂ O, Er ₂ O ₃ , respectively. It has a composition ratio of 3wt, 1-2Wt, GeO ₂ , constitutes ₂ to 3wt of the sol solution when the refractive index is 0.3Δ, 10 to 11wt when the refractive index is 0.75Δ. In addition to the more preferred over the composition ratio of the sol solution for cladding includes _{SiO 2, B 2 O 3,} Na 2 O is 20 to 30 mol, respectively, 70 to 80 mol, 2-3wt.

The sol solution is then placed in a container with an ultrasonic vibrator to produce an aerosol. When ultrasonic waves are used to make an aerosol, when ultrasonic waves pass through the liquid and reach the interface between the liquid and the gas, liquid droplets are produced at the interface, the size of the liquid particles is a function of the density and surface tension of the liquid and the angular frequency of the ultrasonic wave. Therefore, the size of the aerosol can be adjusted by adjusting the density and surface tension of the liquid. In a preferred embodiment of the present invention, ultrasonic waves of 1.5 MHz are used and the size of the aerosol is approximately 4 μm or less.

The aerosol thus produced is deposited on the underclad (when forming the core layer) on the silicon wafer (when forming the core layer) or on the underclad and core (when generating the overclad) using the torch 70 shown in FIG. The aerosol is moved to the torch 70 by argon (Ar) gas, and is deposited on the silicon wafer 60 attached to the wafer holder 50 while being oxidized by an acid and hydrogen flame. At this time, in order to minimize the volatilization of B ₂ O ₃ and P ₂ O ₅ using the temperature controller 110 to maintain the wafer holder 50 200 degrees. In addition, the torch moves in a mesh shape on the XY stage 90 using the computer 100 so that the thickness of the thin film is uniformly deposited.

After deposition, the Si wafer is subjected to a heat treatment process. First, in order to remove the crystal water or organic matter of the deposited powder is heat-treated for 1 hour in an oxygen atmosphere (atmosphere) of 500 degrees. Next, the dried thin film is heat-treated in a tubular furnace for 2 hours to melt the oxide powder. The melting temperature depends on the composition of the thin film, in the present invention is 1250 to 1330 degrees for the core layer, 900-1000 degrees for the over cladding layer. After melting, quenching in air to produce a glass thin film.

3 to 6 are graphs showing characteristics of the glass thin film manufactured using the aerosol process, and FIGS. 3 to 4 are (92-x) SiO ₂ -xB ₂ O ₃ -8P ₂ using the aerosol process described above. 5 and 6 are graphs showing the characteristics of thin films prepared with an O ₅ glass composition, and FIG. 5 and FIG. 6 show the effect of refractive index when GeO ₂ and Er ₂ O ₃ are added to the 62SiO ₂ -30B ₂ O ₃ -8P ₂ O ₅ composition. It is a graph showing the effect. First, Figure 3 is a (92-x) is a graph showing the refractive index and the melting temperature (consolidation temperature) of the glass thin films in the _{SiO 2 -xB 2 O 3 -8P 2} O 5 solution or a thin film to the concentration of B ₂ O _3. As the B ₂ O ₃ content increases from 20 to 70 moles, the refractive index increases from 1.4589 to 1.4683. In general, as the content of B ₂ O ₃ increases in SiO ₂ -B ₂ O ₃ system, the refractive index increases after decrease but slow cooling after melting shows the same results as shown in FIG. 3. This is because as the content of B ₂ O ₃ increases, B ₂ O ₃ having a triangular structure is changed into a tetrahedral structure and the glass structure becomes more dense as Si is substituted, thereby increasing the refractive index.

The refractive index of the glass varies depending on the cooling rate and heat treatment conditions.In the fabrication of the optical amplification device, the under cladding layer undergoes two additional heat treatments when the core layer and the over cladding layer are formed after the layer is formed, and the core undergoes another heat treatment. . For example, after the under cladding is vitrified at 1350 degrees, a core layer is deposited thereon and subjected to a heat treatment at 1320 degrees. The core layer is etched to form a core, and then the overclad is deposited to undergo a final heat treatment at 1000 degrees. Therefore, the change of the refractive index by heat treatment after layer formation is very important.

4 is an experiment of reheating a sample quenched in a tool for 24 hours at a transition temperature after vitrifying the composition of (92-x) SiO ₂ -xB ₂ O ₃ -8P ₂ O ₅ to determine the effect of such heat treatment. After performing, it is a graph showing the change of the refractive index of the glass thin film according to the reheating temperature. The refractive index rapidly rises near the transition temperature, but it can be seen that there is almost no change in the refractive index when reheating at 900 degrees or more. In other words, the vitrification temperature of the core and overclad should be at least 900 degrees in order not to affect the refractive index of the formed underclad layer.

The change rate of the refractive index between the under cladding layer and the core is called Δ. In the experimental results shown in FIGS. 3 to 4, B ₂ O ₃ is 20 and 70 moles, respectively, in order to maximize this value (x = 20, x = 70) yields Δ 0.7. However, the refractive index can be adjusted more easily than this to manufacture various devices. FIG. 5 is a graph showing the refractive index when x wt (x = 2 to 12) GeO ₂ is added to 62SiO ₂ -30B ₂ O ₃ -8P ₂ O ₅ . According to FIG. 5, as the GeO ₂ was increased from 2 to 12, the refractive index increased from 1.4633 to 1.4716. By adding GeO ₂ in this way, various values Δ of 0.3 to 0.75 can be obtained.

FIG. 6 is a graph illustrating a change in refractive index when Er ₂ O ₃ is added, and it can be seen that the refractive index increases as the amount of Er ₂ O ₃ added increases. Therefore, during the generation of the device, the content of B ₂ O ₃ , P ₂ O ₅ , GeO ₂ , Na ₂ O, and Er ₂ O ₃ is appropriately adjusted to obtain a desired refractive index.

In a preferred embodiment of the present invention, when the core layer and the overclad of the optical amplification device is made using an aerosol process, the heat treatment temperature of each layer, the composition ratio (mol) of the resulting thin film and the refractive index of the resulting thin film are shown in Table 2 and same.

The composition ratio of the thin film prepared in Table 2 was measured using EPMA (Elecrton Probe Micro Analysis). As described with reference to FIG. 4, the heat treatment temperature of the overclad was 900 degrees or more in order to prevent a change in the refractive index of the core. In addition, in order not to add a deformation | transformation to the shape of a core, the heat processing temperature of the overclad was 1000 degrees or less. In addition, in the composition ratio range shown in Table 2, the refractive index change rate between the under cladding and the core layer was 0.3 to 1.0Δ.

Under Clad (Thin Film Mole) Core (thin mol) Over clad (thin film mol) SiO ₂ 90-95 50-80 40-70 B ₂ O ₃ 0.5 to 5 0.5 to 1 25-55 P ₂ O ₅ 1 to 10 20 to 45 GeO ₂ 1 to 10 Na ₂ O 0.1 to 5 0.1 to 5 Er ₂ O ₃ 0.1 to 5 Heat treatment temperature (℃) 1300-1350 1250-1330 900-1000 Refractive index (λ (633nm) 1.4580 (± 5 × 10 ^-4 ) 1.4624 to 1.4727 (0.3 to 1.0 Δ ) 1.4575 (± 5 × 10 ^-4 )

More preferably, the underclad, core and overclad are heat treated at 1350 degrees, 1300 degrees and 900 to 1000 degrees, respectively.

As can be seen from Table 4, in the optical amplification device of the present invention, a large amount (20 to 45 mol) of P ₂ O ₅ is added to the core by using an aerosol process, and covalent bonding of SiO ₂ is performed by adding Na ₂ O By cutting off, a large amount of erbium can be added without lumping.

In addition, by adding Na ₂ O to the overclad, the heat treatment temperature of the overclad could be lowered to 900 to 1000 degrees, a temperature not affecting the core.

Although the method for manufacturing the optical amplifying device of the present invention is described only for the embodiment including erbium in the present specification, the optical amplifying device may be used in an optical amplification device including other rare earth metals or an optical amplification device in which Tellurium is added. .

By using a material that can be heat-treated at least (core melting temperature -100 degrees) or less in the overclad, the melting point of the core layer can be widened, so that devices with various functions can be developed. Since no deformation occurs, the reproducibility of production is increased.

By using an aerosol process for the production of the glass thin film constituting the optical amplifying element, a large amount of erbium can be added to the glass thin film without lumping phenomenon. By adding a large amount of erbium, the length of the amplifier can be shortened and a low cost optical amplifier can be manufactured.

Claims (22)

In a planar optical amplifier, Silicon substrate, Underclad, A core formed using an aerosol process, Overclad formed using an aerosol process Flat type optical amplifying device comprising a. The flat panel optical amplifier of claim 1, wherein a refractive index change rate of the underclad and the core is 0.3 to 1.0Δ. The flat panel optical amplifying device of claim 1, wherein the core comprises 0.1 to 5 moles of Er ₂ O ₃ . According to claim 1, wherein the core is 50 to 80 moles of SiO ₂ , 0.5 to 1 mole of B ₂ O ₃ , 20 to 45 moles of P ₂ O ₅ , 1 to 10 moles of GeO ₂ A flat plate amplification device. The flat optical amplifier of claim 1, wherein the core comprises 0.1 to 5 moles of Na ₂ O. The flat type optical amplifying device of claim 1, wherein the overclad comprises 40 to 70 moles of SiO ₂ and 25 to 55 moles of B ₂ O ₃ . The flat optical amplifier of claim 1, wherein the overclad comprises 0.1 to 5 moles of Na ₂ O. In the manufacturing method of flat plate optical amplification Forming an underclad on a silicon substrate, Forming a core layer using an aerosol process, Etching the core layer to form a core; Forming an overclad using an aerosol process Method for manufacturing a flat plate optical amplifying device comprising a rule The method of claim 8, wherein the forming of the core layer Forming a sol solution, Forming an aerosol using the sol solution, Depositing the aerosol on the underclad; Heat-treating and melting the deposited aerosol, Cooling the molten aerosol to form a glass thin film Method for manufacturing a flat plate optical amplifying device comprising a The method of claim 9, wherein the heat treatment includes heat treatment at 1250 degrees to 1330 degrees. The method of claim 9, wherein the sol solution comprises 0.2 to 5 wt% of Er ₂ O ₃ . The method of claim 9, wherein the sol solution contains 1 to 2 wt% of Er ₂ O ₃ . The sol solution of claim 9, wherein the sol solution comprises 30 to 70 mol of SiO ₂ , 5 to 10 mol of B ₂ O ₃ , 25 to 65 mol of P ₂ O ₅ , and 2 to 12 wt of GeO ₂ . Amplification device manufacturing method. The plate according to claim 9, wherein the sol solution comprises 40 to 50 moles of SiO ₂ , approximately 5 moles of B ₂ O ₃ , 45 to 55 moles of P ₂ O ₅ , and 2 to 3 wt or 10 to 11 wt of GeO ₂ . Fluorescent amplifier device manufacturing method. The method of claim 9, wherein the sol solution comprises 0.5 to 5 wt% of Na ₂ O. 11. The method of claim 9, wherein the sol solution comprises 2 to 3 wt% of Na ₂ O. 11. The method of claim 8, wherein the overclad forming step Forming a sol solution, Forming an aerosol using the sol solution, Depositing the aerosol on the core and underclad; Heat-treating and melting the deposited aerosol, Cooling the molten aerosol to form a glass thin film Method for manufacturing a flat plate optical amplifying device comprising a The method of claim 17 The heat treatment step is an optical amplification device manufacturing method comprising the heat treatment at 900 degrees to 1000 degrees. The method of claim 17, wherein the sol solution comprises 20 to 50 moles of SiO ₂ and 50 to 80 moles of B ₂ O ₃ . The method of claim 17, wherein the sol solution comprises 20 to 30 moles of SiO ₂ and 70 to 80 moles of B ₂ O ₃ . 18. The method of claim 17, wherein the sol solution contains 0.5 to 5 wt% of Na ₂ O. 18. The method of claim 17, wherein the sol solution contains 2 to 3 wt% of Na ₂ O.