KR20030033143A - Method for fabricating planar waveguide type optical amplifier using glass sputtering - Google Patents

Abstract

PURPOSE: A method for fabricating a planar lightwave circuit type optical amplifier using glass sputtering is provided to obtain low waveguiding loss and good gain characteristics by depositing a glass containing a high density rare-earth element. CONSTITUTION: According to the method for fabricating a planar lightwave circuit type optical amplifier, a silica clad layer(401) is formed on a silicon substrate. The silica clad layer is etched in intaglio. A glass film(404) containing a rare-earth element is deposited on the intaglio-etched silica clad layer. And a top clad layer(405) is formed on the glass film containing a rare-earth element. The above silica clad layer is formed as thick as 15-20 micro meter using FHD(Flame Hydrolysis Deposition), PECVD(Plasma Enhanced Chemical Vapor Deposition) or HIPOX. And the etching of the silica clad layer is performed using an ICP(Inductively Coupling Plasma) etching method with a metal mask.

Description

Method for manufacturing planar waveguide optical amplifier using glass sputtering {METHOD FOR FABRICATING PLANAR WAVEGUIDE TYPE OPTICAL AMPLIFIER USING GLASS SPUTTERING}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar waveguide optical amplifier for optical communication, and more particularly, to manufacturing a planar waveguide optical amplifier capable of high-gain amplification transmission of signal light by depositing a glass containing a high concentration of rare earth on an intaglio portion of silica. It is about a method.

In the case of long-distance transmission, the optical signal of 1550nm band used as signal light is gradually weakened by noise or loss of transmission line as it passes through the transmission line. In order to solve the weakening of the optical signal as described above, an optical amplifier that amplifies the optical signal is used.

Conventionally, an optical amplifier using an optical fiber is mainly used, and FIG. 1 illustrates a basic structure of a fiber type optical amplifier using a conventional optical fiber. In Fig. 1, reference numeral 101 denotes a signal light input, 102 denotes a signal light output, 103 denotes a pump leisure diode, 104 denotes a wavelength multiplexer, 105 denotes an isolator, and 106 denotes a rare earth-added optical fiber.

As described above, the conventional fibrous optical amplifier has a limited rare earth metal ion content which can be doped to the rare earth-added optical fiber, and requires a very long rare earth-added optical fiber of several tens of meters (17-50 m), and a separate wavelength multiplexer. (WDM) and isolator are required. Therefore, there is a problem that the size of the optical amplifier is large and mass production is difficult.

In order to solve the problems of the fiber type optical amplifier, a planar waveform optical amplifier has been proposed. The basic structure of a conventional planar waveguide optical amplifier is shown in FIG. In Fig. 2, 201 is a rare earth addition planar waveguide device, and 202 is a pump laser diode, respectively.

As described above, the conventional planar waveguide optical amplifier replaces the rare earth-added optical fiber with a rare earth-added waveguide device, and the optical waveguide containing rare earth metal ions generally has a large transmission loss value for signal light and pump light. The large loss rare earth-containing waveguides do not allow the integration of a number of functional devices that can be made into a low loss waveguide into a waveguide optical amplifier. In addition, in order to combine the signal light and the pump light, a wavelength multiplier made of optical fiber must be attached to the outside.

The present invention is to solve the problems of the prior art as described above, a planar waveguide optical amplifier which can obtain a low wave loss and excellent gain characteristics by depositing a high concentration of rare earth-containing glass on the intaglio-etched portion of silica by sputtering The purpose is to provide a method of manufacturing.

1 is a basic structural diagram of a conventional fiber type optical waveguide,

2 is a basic structural diagram of a conventional waveguide type optical amplifier,

3 is a configuration diagram of a low loss waveguide device in which a conventional wavelength multiplexer is integrated;

4A to 4D are cross-sectional views illustrating a method of manufacturing the optical amplifier according to the first embodiment of the present invention;

5 is a configuration diagram of a sputtering apparatus,

6A to 6G are cross-sectional views illustrating a method of manufacturing an optical amplifier according to a second embodiment of the present invention;

7 shows a structural example in which a functional passive device is combined with an optical amplifier of the present invention;

* Description of the symbols for the main parts of the drawings *

401: lower clad layer 402: metal mask

403: intaglio etching section 404: rare earth-containing glass film

405: upper cladding layer 501: sputtering target

502 collimator 503 sputtering bundle

504 substrate 601 silicon or silica substrate

602: low loss waveguide buffer layer 603: low loss waveguide core layer

604: metal mask 605: etched core layer

606: upper cladding layer 607: optical amplifier section

608: rare earth-containing glass film 609: upper clad layer

The present invention for achieving the above object comprises the steps of forming a silica clad layer on a silicon substrate; Negative etching the silica clad layer; Depositing a rare earth-containing glass film on the etched silica clad layer; It provides a method for producing a planar waveguide optical amplifier comprising the step of forming an upper clad layer on the rare earth-containing glass film.

The silica clad layer is formed to a thickness of 15-20㎛ using one of FHD, PECVD, HIPOX, the negative etching of the silica clad layer is 8-10㎛ in width by ICP etching method using a metal mask depth Etch to be 7-14㎛. One metal film of Cr or Al is used as the metal mask.

The rare earth-containing glass film deposits 1.5-2 μm of either phosphate glass or soda-lime glass containing 2-4 wt% of rare earth metal by sputtering or electron beam method. When the rare earth-containing glass film is deposited, sputtering bundles are formed by using low pressure sputtering or collimator of 2 mmtorr or less so as to be deposited in the depth direction of the intaglio etching.

The collimator is made of a metal of tantalum, and is configured perpendicularly between the sputtering target and the substrate at intervals of 3-4 mm with a thickness of 0.2-0.3 μm and a width of 5-10 μm.

The upper clad layer is formed in a structure surrounded by the upper clad layer by spin coating a refractive index matching polymer or gel on the rare earth-containing glass film.

In addition, the present invention is characterized by providing a planar wave-type optical amplifier combining the high-efficiency amplification and the functional element by constructing the optical amplifier manufactured by the method of claim 1 on the same substrate as the low loss silica functional element.

As the low loss silica functional element, a planar wave type optical amplifier manufactured by combining a low loss optical distribution device such as 8, 16, 32 channels and the optical amplifier manufactured by the method of claim 1 with a lossless distribution or amplification distribution function on the same substrate or The low-loss silica functional device combines an AWG-WDM device such as 8, 16, 32 channels, etc. with an optical amplifier manufactured by the method of claim 1 to amplify the input signal and compensate for insertion loss, thereby improving the quality of the WDM on the same substrate. A planar waveguide optical amplifier is provided.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to describe the present invention in more detail.

3 illustrates a basic structure of a low loss waveguide device in which a general wavelength multiplexer is integrated.

Referring to FIG. 3, the low loss waveguide includes a core layer, which is a region where light is guided, and a lower cladding layer 301 and an upper cladding layer 302 having a lower refractive index than the core layer, wherein the core layer is a signal light input waveguide core. Layer 303, pumped light input waveguide core layer 304 and signal light output waveguide core layer 305. In FIG. 3, reference numeral 306 denotes a wavelength multiplexer integrated in the waveguide.

The low loss waveguide device is a silica glass waveguide manufactured by a method such as Flame Hydrolysis Deposition (FHD), Plasma Enhanced Chemical Vapor Deposition (PECVD) or a waveguide by ion exchange (ion exchange) to a low loss optical glass. To form.

The low-loss optical waveguide device is an optical waveguide device without the addition of rare earth metal ions, and has no optical amplification effect, but can transmit signal light and pump light with low loss, and integrate functional devices such as a wavelength multiplexer and an optical splitter with low loss. have.

The optical amplifier of the present invention can be applied to all of the above-described low loss waveguide manufacturing method, and will be described below with particular focus on the FDH (flame hydrolysis deposition) method.

On the other hand, in the optical waveguide device containing rare earth metal ions such as Er, Nd, Pr, and Yb, when the pumping light and the signal light are transmitted at the same time, part of the pumping light energy is transferred to the signal light due to the electron transition, so that amplification of the signal light occurs. Waveguide device.

Such a waveguide uses glass made by adding a certain amount of rare earth metal ions such as Er, Nd, Pr, and Yb to silicate or phosphate glass containing electron monovalent and divalent alkali metal ions such as Na, K, Ca, and Mg. Manufacture. Rare earth metal ions may be present in the core portion of the waveguide or uniformly present in the entire base material.

Rare earth ion-added optical waveguide devices can precisely etch glass films made by sputtering, electron beam, flame hydrolysis (FHD), chemical vapor deposition (CVD), and aerosol deposition, After the waveguide pattern is formed in, it can be produced using a method such as ion exchange. The present invention exemplifies a waveguide device in which a base material such as soda-lime or phosphate glass containing rare earth metal ions is deposited by sputtering or electron beam to form a waveguide.

The present invention is a method of manufacturing a planar waveguide optical amplifier by implementing the low-loss optical waveguide device and the optical waveguide device containing rare earth metal ions on the same substrate. The basic optical amplifier can be manufactured separately regardless of the low loss waveguide device. However, if the low loss waveguide device is configured on the same substrate, the manufacturing process is different. Accordingly, in the present invention, after fabricating a low-loss waveguide device such as a wavelength multiplexer and a splitter and an AWG-WDM (Arrayed Waveguide Grating WDM) in which signal light and pumping light are input, the optical amplification section is defined and engraved to amplify the rare earth-containing glass. It is produced by depositing on the section.

4A to 4D are cross-sectional views illustrating a method of manufacturing an optical amplifier using silica engraved etching according to a first embodiment of the present invention.

First, as shown in FIG. 4A, a lower clad layer 401, which is a buffer oxide film, is formed on the silicon substrate using a FHD, PECVD, HIPOX, or the like to have a thickness of 15-20 μm in consideration of an intaglio etching. In this case, when using a silica substrate, the silica substrate is used as the lower clad layer without forming a separate clad layer.

On the substrate on which the lower clad layer 401 is formed, one of an Al layer and a Cr layer is deposited as a metal mask layer 402 to a thickness of 2000 to 3000 m 3. The deposited metal mask layer 402 is patterned through a conventional photolithography process to define an intaglio etching section 403 of silica.

As shown in FIG. 4B, the lower clad layer 401 or silica is etched using the patterned metal mask layer 402. In this case, an intaglio etching of the lower clad layer 401 or silica is performed using an inductively coupled plasma (ICP) etching method, and CF ₄ and O ₂ are used as etching gases. The width of the intaglio etching is 8-10㎛, and the depth is 7-14㎛. The verticality of the sides of silica etched by ICP etching method is more than 86 ° and close to vertical.

As shown in FIG. 4C, the rare earth-containing glass 404 is deposited on the negatively etched lower clad layer 401 or silica by sputtering or electron beam.

A method of depositing the rare earth-containing glass 404 by the sputtering method will now be described with reference to FIG. 5. 5 shows a sputtering schematic diagram formed by inserting the collimator 502 between the sputtering target 501 and the substrate 504.

Sputtering target (sputtering target, 501) consists of a general water-cooled sputter gun, the diameter of the glass is used 2-4 inches (50-100mm), 1/4 inch (6mm).

In general, sputtering is processed in several tens of mmtorr, so that deposition on the etched side becomes a problem. In the present invention, a low pressure process of 1-2 mmtorr reduces the scattering of sputtered particles.

Induction deposition in the engraved depth direction induces progression in the same direction as the method of making bundles of sputtered particles with a mean free path of 1 m or more with a process pressure of 10 ^-5 torr or less and more than 1 m. There is a method using a collimator (502).

The method of lowering the process pressure decreases the deposition rate below 100 kW / hr, which is not suitable for thick film deposition. Even in the case of using the collimator 502, the deposition rate is low, such as 1000-2000 Pa / hr, it is difficult to form a thick film.

The collimator 502 has a structure of 0.2-0.3 mm in thickness and 5-10 mm in width with a metal material such as tantalum (Ta) to maintain a 3-4 mm spacing and to stand vertically. The sputtering gas passing through the collimator 502 forms a bundle 503 in a direction perpendicular to the substrate and is deposited on the substrate. At this time, the substrate temperature is maintained at 300-400 ℃ heating.

As the material of the rare earth-containing glass, phosphate glass or soda-lime glass containing 2-4 wt% of rare earth oxide is used. Sputtering thickness of the glass film 404 is deposited to 1.5-2㎛, wherein the difference Δn of the refractive index with the lower cladding layer 401 according to the refractive index of the glass base material is about 1-3%. The deposited rare earth-containing glass 404 is stabilized by heating to 600-700 ° C. for 2 hours.

The upper cladding layer 405 is formed on the rare earth-containing glass film 404 by using a refractive index matching polymer or gel by spin coating to manufacture the optical amplifier of the present invention. The glass deposited outside the amplification section is not removed separately, and the amplification gain characteristic depends on the rare earth content and the state of the glass film, and has a gain characteristic of 3-4 dB / cm.

6A to 6G illustrate a process cross-sectional view of implementing the low loss waveguide device and the optical amplifier of the present invention on the same substrate.

First, as shown in FIG. 6A, the lower cladding layer 602, which is a low loss waveguide buffer layer, and the low loss waveguide core layer 603 are deposited on the silicon substrate or the silica substrate 601 at 15 μm and 6 μm by FHD, respectively, and FIG. 6B. As described above, a metal film is deposited and then lithography to form a metal mask 604.

As shown in FIG. 6C, the core layer 603 is etched using the metal mask 604. An upper cladding layer 606 is deposited on the etched core layer 605 as shown in FIG. 6D by 10 µm by FHD. After the photoresist film 607a is deposited on the upper cladding layer 606, an optical amplification section 607 is defined by a lithography process.

As shown in FIG. 6E, the upper cladding layer 606 of the optical amplification section 607 is etched by 14 μm using the photosensitive film 607a as a mask. At this time, the depth of the intaglio etching is adjusted to match the center of the core layer 605 of the low loss silica waveguide.

A rare earth-containing glass film 608 is deposited on the intaglio-etched substrate as shown in FIG. 6F, and an upper clad layer 609 is formed as shown in FIG. 6G.

FIG. 7 is a plan view of an eight-channel distributor 704, an eight-channel AWG-WDM device 705, and an optical amplifier 703 in the low-loss waveguide device on the same substrate 701. The structure of the wavelength multiplexer 702 for the signal light and pump light entrance is also composed of a low loss silica waveguide. The length of the optical amplification section combined with the eight channel splitter 704 is distributed at the same intensity as the input signal light with a lossless loss at 2 cm. The 3cm amplification section is implemented with an 8-channel branch amplifier that compensates for losses and generates about 5dB of gain. In the case of the 8-channel AWG-WDM 705, the gain required to compensate for the weak signal at the input stage and to compensate for the insertion loss of the device 3dB generated by the wavelength multiplexing is about 10dB and the amplification section length is 3cm.

According to the present invention as described above, by inserting and depositing a glass medium having a high amplification efficiency into the silica clad layer having excellent optical characteristics, it is possible to implement an optical amplifier having low waveguide loss and excellent gain characteristics. In addition, although the present invention differs depending on the rare earth metal content and distribution of the glass in the amplification section, gain characteristics of 3-4 dB per single length (cm) can be obtained at a rare earth content of 2% or more, so that the optical amplifier can be miniaturized and reduced in price. Can contribute.

In addition, the same substrate integration process of the low-loss silica element in the high efficiency amplifier is easy, and even if only the amplifier is configured, the configuration of the wavelength multiplexer combining the signal light and the pump light can be simplified, thereby achieving miniaturization and high efficiency. In addition, since the present invention makes a low-loss waveguide device and then makes an optical amplification waveguide device separately, a process most suitable for each device can be used.

In addition, in the present invention, when the 8-channel splitter, 8-channel AWG-WDM element, and the optical amplifier are implemented on the same substrate among the low-loss waveguide elements, the structure of the wavelength multiplexer for the signal light and the pump light inlet is also composed of the low-loss silica waveguide. The length of the optical amplification section combined with the splitter is distributed in the same intensity as the input signal light with lossless distribution at 2cm, and an 8-channel branched heavy amplifier with gain of about 5dB at 3cm is implemented, so in the case of 8-channel AWG-WDM The device's functionality can be improved by compensating for the weak signal at the input stage at 3cm and compensating for the insertion loss of 3dB caused by wavelength multiplexing.

Therefore, the low loss waveguide can be integrated with various functional devices, and the optical amplifier can be manufactured by optimizing only the amplification characteristics, so that the amplifier can be manufactured according to the present invention. It can be maximized.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (11)

Forming a silica clad layer on the silicon substrate; Negative etching the silica clad layer; Depositing a rare earth-containing glass film on the etched silica clad layer; And And forming an upper clad layer on the rare earth-containing glass film. The method of claim 1, The silica clad layer is formed of a thickness of 15-20㎛ using one of FHD, PECVD or HIPOX method of manufacturing a planar waveguide optical amplifier. The method of claim 1, The engraved etching of the silica clad layer is etched to a width of 8-10㎛ and 7-14㎛ depth by ICP etching method using a metal mask. The method of claim 3, wherein The metal mask is a method of manufacturing a planar waveguide optical amplifier, characterized in that a metal film of Cr or Al is used. The method of claim 1, The rare earth-containing glass film is a method of manufacturing a planar waveguide optical amplifier, characterized in that one of the phosphate glass or soda lime glass containing 2-4wt% rare earth metal is deposited by sputtering or electron beam method. The method of claim 5, When the rare earth-containing glass film is deposited to form a sputtering bundle by using a low pressure sputtering or collimator of 2mmtorr or less so as to be deposited in the depth direction of the intaglio etching method of manufacturing a planar waveguide optical amplifier. The method of claim 6, The collimator is made of a metal of tantalum, manufacturing method of planar waveguide optical amplifier, characterized in that the vertical configuration between the sputtering target and the substrate at intervals of 3-4mm with a thickness of 0.2-0.3㎛, 5-10㎛. The method of claim 1, The top clad layer is a planar waveguide optical amplifier manufacturing method characterized in that the spin-coated refractive index matching polymer or gel on the rare earth-containing glass film is formed in a structure surrounding the upper clad layer. A planar waveguide optical amplifier in which an optical amplifier manufactured by the method of claim 1 and a low loss silica functional device are implemented on the same substrate to combine high efficiency amplification and a functional device. The method of claim 9, The low loss silica functional device is a planar waveguide optical amplifier, characterized in that the low-loss optical distribution device of any one of channels 8, 16 or 32. The method of claim 10, The low loss silica functional device is a planar waveguide optical amplifier, characterized in that the AWG-WDM device of any one of channels 8, 16 or 32.