KR100363887B1 - Fabrication method of hybrid coupled planar waveguide type optical amplifier - Google Patents

Abstract

The present invention relates to a heterojunction planar waveguide type optical amplifier and a method for manufacturing the same. A low loss optical waveguide element into which a signal light and a pumping light are incident, and an amplification optical waveguide element containing rare earth metal ions such as Er and Nd are combined. Provided are a planar waveguide optical amplifier with a structure of the present invention and a method of manufacturing the same.

In addition, the present invention provides an optical amplification application device to compensate for the signal attenuation generated in the device by combining with a device (Planar Lightwave Circuit) such as a splitter, a wavelength multiplexer using an amplifier having such a structure.

According to the present invention, the low loss waveguide can be integrated with various functional elements, and the optical amplifier is optimized only by amplifying characteristics, and it is possible to manufacture an optical amplifier by combining two separately manufactured waveguide elements. Both the amplification effect and the device's function can be maximized.

Description

Heterojunction planar waveguide type optical amplifier and its manufacturing method {Fabrication method of hybrid coupled planar waveguide type optical amplifier}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar waveguide type optical amplifier used in optical communication technology. More specifically, the present invention relates to a waveguide having a low loss waveguide and rare earth metal ions mainly intended for the transmission of signal light and pumped light. The present invention relates to an efficient planar waveguide type optical amplifier having the advantages of low loss transmission and optical amplification which each waveguide element has by combining each other, and a method of manufacturing the same.

In the case of long-distance optical communication, the optical signal of 1550nm band, which is used as signal light, is gradually weakened by noise or loss of transmission line as it passes through the transmission line. Therefore, in order to solve this problem, an optical amplifier for amplifying an optical signal is used.

Conventionally, as shown in FIG. 1, an isolator 105, a pump laser diode 103, a wavelength multiplexer 104, and a rare earth-added optical fiber 106 are composed of fibers using optical fibers that amplify and output the input signal light. Fluorescent amplifiers are mainly used.

However, such a conventional optical fiber amplifier requires a very long rare earth-added optical fiber of several tens of meters due to the limited content of rare earth metal ions which can be doped into the rare earth-added optical fiber, and a separate wavelength multiplexer (WDM) This necessitates an increase in the size of the optical amplifier and has a difficult problem in mass production.

As a method for solving the above problems, planar waveguide optical amplifiers are considered. However, in the case of the conventional planar waveguide optical amplifier, as shown in FIG. 2, the rare earth-added optical fiber portion of the optical fiber amplifier is replaced with the rare earth-added waveguide device 206. Accordingly, there is still a problem in that an accessory optical circuit such as the wavelength multiplexer 204 is still needed.

In addition, optical waveguides containing rare earth metal ions used to manufacture planar waveguide optical amplifiers generally have very large transmission loss values for signal light and pumped light. Therefore, it is impossible to integrate various functional elements that can be made into a low loss waveguide into a waveguide optical amplifier using only such a large loss rare earth-containing waveguide. In addition, in order to combine the signal light and the pumping light, the wavelength multiplexer made of optical fiber must be attached to the outside.

In addition, the prior art related to the planar optical amplifier includes a WDM coupler integrated in a high concentration co-doped Er planar wave, resulting in a loss effect generated by the WDM coupler, but a high gain characteristic due to the offset caused by the optical amplification. The optical amplifier has been miniaturized and has a low price [Reference: K. Hattori et al., "Erbium-doped Sillica-based Waveguide Amplifer Integrated with a 980 / 1530nm WDM Coupler, Electronics Letters, Vol. 30, No. 11, pp.856-857 , 1994. 11]

In this prior art, SiO ₂ is castable and phosphorus is co-doped. If Er is added in a predetermined amount or more, Er is clustered together with scattering loss, and thus an optical amplification effect cannot be obtained. The limited addition of Er, which is described here as a certain amount (<0.5wt%), becomes a factor to obtain the optical amplification effect when the length of the Er-added waveguide is lengthened by several ten cm or more. That is, there is a disadvantage in that the size of the device increases, and the integration of the low loss waveguide and the Er addition waveguide is limited by the increase in the length of the Er addition waveguide.

SUMMARY OF THE INVENTION An object of the present invention devised to solve the conventional problems as described above is an optical amplification waveguide containing a low loss optical waveguide element and rare earth metal ions capable of integrating functional elements such as a wavelength multiplexer and an optical splitter. The present invention provides a method for manufacturing a planar waveguide type optical amplifier capable of simultaneously integrating and amplifying various types of low-loss functional devices by separately manufacturing the devices and bonding them to each other.

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 low loss waveguide device incorporating a wavelength multiplexer;

4 is a rare earth addition waveguide device prepared by the ion exchange method

5 is a cross-sectional view of a heterojunction planar waveguide optical amplifier manufacturing process of the present invention;

6 is a structural diagram of a planar waveguide type optical amplifier according to an embodiment of the present invention.

7 is a structural diagram in which a functional passive device is combined with an optical amplifier according to an embodiment of the present invention;

Explanation of symbols on the main parts of the drawings

101, 201: signal light input 102, 202: signal light output

103, 203: pump laser diode 104, 204: wavelength multiplexer

105, 205: isolator 106: rare earth addition optical fiber

206: rare earth addition planar waveguide device

300: low loss optical waveguide device 301: buffer layer

302: upper cladding layer 303: signal light input waveguide core

304: pumping light input waveguide core 305: signal light output waveguide core

400: optical waveguide device for amplifying rare earth metal ions

401: Rare earth-added base material glass (Er-containing silicate glass)

402 metal thin film 403 KNO ₃ molten salt

404: waveguide for optical amplification formed by ion exchange

501: spring 601: silicon or silica substrate

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

604: metal (aluminum, chrome, etc.) mask

605: etched waveguide core layer 606: low loss waveguide upper cladding layer

607: exposed portion of the low-loss waveguide upper layer (waveguide device coupling portion for rare earth ion-added optical amplification)

608: waveguide device for optical amplification containing rare earth metal ions

701: silicon or silica substrate 702: wavelength multiplexer

703: waveguide device for optical amplification containing rare earth metal ions

704: 16 channel optical splitter

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, as a component of the planar waveguide optical amplifier of the present invention, a low loss optical waveguide device is an optical waveguide device without addition of rare earth metal ions, and has no optical amplification effect, but can transmit signal light and pumped light with low loss. Functional elements such as a wavelength multiplexer and an optical splitter having low loss can be integrated.

The waveguide is generally composed of a core layer, which is a region where light is guided, and a buffer layer and an upper cladding layer having a lower refractive index. The low loss waveguide device may be manufactured by forming a waveguide in a silica glass waveguide manufactured by a method such as flame hydrolysis and chemical vapor deposition or a method of ion exchange or the like in a low loss optical glass.

3 illustrates a low loss optical waveguide device in which a wavelength multiplexer is integrated as an example, and may be manufactured through the same process as in Example 1 described later.

Meanwhile, an optical amplification waveguide device containing rare earth metal ions such as Er, Tm, Pr, and Yb, which is another component of the planar waveguide optical amplifier of the present invention, is part of the pumped light energy when the pumped light and the signal light are simultaneously transmitted. Is a waveguide device in which amplification of signal light occurs while being transferred to signal light by an electron transition action.

Such a waveguide uses glass made by adding a certain amount of rare earth metal ions such as Er, Tm, Pr, and Yb to silicate or phosphate glass containing electrons monovalent and divalent alkali metal ions such as Na, K, Ca, and Mg. Manufacture. Rare earth metal ions may be present in the waveguide core portion or may be uniformly present throughout the substrate. Rare earth ion-added optical waveguide devices can precisely etch glass films made by sputtering, Flame Hydrolysis Deposition (FHD), Chemical Vapor Deposition (CVD), Aerosol deposition, or the like. After forming the waveguide pattern, it can be produced using a method such as ion exchange.

4 shows a manufacturing process of a rare earth-added waveguide device manufactured by an ion exchange method as an example, and may be manufactured through the following process.

First, a metal (Al) thin film 402 having a thickness of 2000 Å is formed on the silicate glass 401 containing 2 wt% Er ions by thermal evaporation.

Subsequently, a waveguide pattern is formed through photolithography and wet etching, and then impregnated in KNO ₃ salt 403 melted at 380 ° C. for 1 hour to exchange Na ions of the silicate glass 401 with K ions for optical amplification waveguide ( After forming 404, the Al thin film is removed with an acid solution to complete the waveguide device for optical amplification.

FIG. 5 shows the structure of the planar waveguide optical amplifier of the present invention, wherein the low loss optical waveguide device 300 and the optical waveguide device 400 containing rare earth metal ions are bonded to each other.

The rare earth metal ion-containing optical waveguide device 400 is positioned at an upper end of the low-loss waveguide, which is broken from each other. In this case, a part of the rare-earth-containing waveguide overlaps with the upper end of the low-loss waveguide so that the signal light and pumping light are upper in the low-loss waveguide at the input stage. It is naturally moved toward the waveguide containing rare earth metal ions, and after optical amplification occurs, it is moved to the low loss waveguide of the lower output stage to be output.

The length of the overlapping portion of each waveguide element can be determined by calculating the signal and pumping light so that the light and pumping light can be transferred with the least loss from known mathematical methods such as the coupled mode theory.

Each waveguide device may be bonded to a UV cured epoxy, or may be simply fixed using a spring 501 or the like. At this time, in order to reduce the light loss, a UV-cured infrared transmission epoxy is used between both waveguide elements or a low loss medium such as a refractive index matching liquid is filled. For precise alignment of each waveguide, a portion of the cladding layer of the low loss waveguide may be processed by etching or the like to make a mounting position of the waveguide device to which rare earth metal ions are added.

Hereinafter, a method of manufacturing a planar waveguide optical amplifier according to the present invention will be described.

Example 1

Figure 6 shows a cross-sectional view of a heterojunction waveguide optical amplifier manufacturing process according to an embodiment of the present invention.

First, a 20 µm buffer layer 602 having a refractive index difference Δn of 0.3 to 0.75% and a 6 to 8 µm core layer 603 are formed on the silicon substrate 601 by flame hydrolysis.

After forming a metal (Cr, AL) mask 604 having a thickness of 2000Å by thermal evaporation thereon, a waveguide pattern is formed through photolithography and wet etching.

Thereafter, after etching the wavelength multiplexer and the signal light transmission waveguide 605 which combine the signal light of 1550 nm wavelength and the pumped light of 980 nm through inductive coupled plasma (ICP) etching, the metal film is removed, and the flame hydrolysis method is applied thereon. The upper clad layer 606 is formed by using.

Thereafter, the upper cladding layer 606 is exposed to photolithography and etching to form an exposed portion 607 in order to couple the waveguide device for optical amplification.

Subsequently, the rare earth metal ion-containing amplification optical waveguide device 608 made by the same process as in FIG. 4 was precisely processed to obtain an appropriate size, and then applied to the exposed portion 607 of the low loss waveguide device by applying ultraviolet curing epoxy. Then, the signal light is incident and the transmission loss is measured. The position of the upper waveguide device for fine amplification is finely adjusted to minimize the loss of signal light, and then the ultraviolet rays are irradiated to cure the epoxy to attach the elements to each other to complete the planar waveguide type light attenuator.

Example 2

First, a low loss waveguide device is manufactured in the same manner as in Example 1 .

In addition, the waveguide device for optical amplification is manufactured by using the ion exchange method as shown in FIG. 4 described above with the phosphate glass to which 2% Er ions and 5% Yb ions are added together.

Thereafter, the refractive index matching liquid having a refractive index of 1.5 is uniformly applied to the upper end of the low loss waveguide device, and then the optical amplification waveguide device is placed and pressed with a pre-made spring 501 to be combined as shown in FIG. 5.

Example 3

Embodiments 1 and 2 show the basic elements of the optical amplifier configuration, and can be manufactured by integrating the elements having different functions (optical divider, multi-channel Wavelength Division Multiplexer (WDM), etc.) in the low loss silica waveguide.

7 shows an embodiment in which a functional passive element (16 channel lossless optical splitter) is combined with an optical amplifier of the present invention. First, a plurality of wavelengths are multiplexed on a silicon or silica substrate 701 in the same manner as in Example 1. The firearm 702 and the 16 channel optical splitter 704 are formed as a low loss waveguide to manufacture a low loss optical waveguide device.

Then, the rare earth metal ion-containing optical waveguide element 703 manufactured in the same manner as in Example 1 or Example 2 described above is bonded on the portion where the low loss waveguide of the low loss optical waveguide element is cut off, and is placed on one substrate. Several optically amplified functional devices are manufactured. In this case, the method of combining the low loss optical waveguide device and the optical amplification waveguide device is also the same as in the first or second embodiment .

In addition, although not illustrated here, the present invention may be manufactured by applying to a device such as a multi-channel WDM, an optical transmission / reception module, a WDM-PON (Passive Optical Network) module, or the like.

As described above, since the present invention manufactures a planar waveguide type optical amplifier by simply facing each other by combining heterogeneous waveguide elements made by different processes, a process most suitable for each element can be used.

For example, in the process where it is difficult to add rare earth metal ions such as flame hydrolysis, only low loss waveguide devices are manufactured.On the other hand, the base glass to which rare earth metal ions are added is ion-exchanged to make a waveguide device for optical amplification, which is then flavored and combined In the case of making an optical amplifier, it is possible to make the optical amplifier simpler than the conventional technology in which the two waveguides are configured in the same process or on the same substrate.

According to the present invention, a low loss waveguide can be integrated with various functional elements, and an optical amplifier can be manufactured by optimizing only the amplification characteristics so as to combine the two waveguide elements with each other to manufacture an optical amplifier. Maximizes the full functionality of the device.

The technical spirit of the present invention has been described above with reference to the accompanying drawings, but this is by way of example only and not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (12)

Amplifying optical waveguide device comprising a wavelength multiplexer combining signal light and pumped light and a low loss optical waveguide device composed of a low loss waveguide and a waveguide containing rare earth metal ions. The amplifying optical waveguide device is positioned above the low-loss waveguide of the low-loss optical waveguide device, and the two optical waveguide devices are combined to form a structure in which a part of the rare earth metal ion-containing waveguide overlaps the upper portion of the low-loss waveguide. Heterojunction planar waveguide type, characterized in that the signal and pumping light is naturally moved toward the waveguide containing the rare earth metal ions in the upper end of the low loss waveguide at the input stage and then moved to the low loss waveguide at the lower output stage for output. Optical amplifier. The method of claim 1, The combination of the low loss optical waveguide device and the amplifying optical waveguide is a heterojunction planar waveguide optical amplifier, characterized in that using a UV curing epoxy, or a spring. The method of claim 1, The coupling of the low loss optical waveguide element and the amplification optical waveguide element is performed by processing a part of the cladding layer of the low loss waveguide by etching or the like to prepare a coupling space for mounting the amplification optical waveguide element therein. A heterojunction planar waveguide optical amplifier. The method according to claim 2 or 3, The heterojunction planar waveguide optical amplifier of claim 1, wherein a low loss medium such as UV cured infrared ray transmissive epoxy or a refractive index matching solution is filled in a coupling portion between the low loss optical waveguide device and the amplification optical waveguide. It consists of a wavelength multiplexer that combines signal and pumping light, which are made of individual elements, and an optical waveguide element for amplification, which consists of a low loss optical waveguide element consisting of a low loss waveguide and a passive waveguide containing rare earth metal ions. The amplifying optical waveguide device is positioned above the low-loss waveguide of the low-loss optical waveguide device, and the two optical waveguide devices are combined to form a structure in which a part of the rare earth metal ion-containing waveguide overlaps the upper portion of the low-loss waveguide. In the low loss waveguide of the input stage, the signal and pumping light is naturally moved toward the waveguide containing the rare earth metal ions on the upper side, and after the optical amplification occurs, it is moved to the low loss waveguide of the output stage at the bottom so that the functional passive element is included. Heterojunction planar waveguide optical amplifier. Manufacturing a low loss optical waveguide device comprising a wavelength multiplexer combining the signal light and the pumped light and a signal loss transmission waveguide; A step of manufacturing an amplifying optical waveguide device composed of a waveguide containing rare earth metal ions; And And a step of coupling the two optical waveguide elements. The method of claim 6, The process of manufacturing the low loss optical waveguide device, Forming a buffer layer and a core layer having a predetermined refractive index difference using a flame hydrolysis method or the like on a silicon substrate; Forming a metal mask having a predetermined thickness through thermal evaporation on the core layer, and then forming a waveguide pattern constituting a signal multiplexer and a wavelength multiplexer that combines signal light and pumped light through photolithography and wet etching; And And removing the metal film after etching the wavelength multiplexer and the signal light transmission waveguide which combine the signal light and the pumped light through the inductively coupled plasma etching, and forming an upper clad layer by using the flame hydrolysis method thereon. A heterojunction planar waveguide optical amplifier manufacturing method. The method of claim 6, The process of manufacturing the amplifying optical waveguide device, Thermally depositing a metal thin film having a predetermined thickness on the silicate glass containing Er ions; After forming a waveguide pattern through photolithography and wet etching, impregnating the molten KNO ₃ salt for a predetermined time to exchange Na ions of silicate glass with K ions to form a waveguide, and then remove the metal thin film with an acid solution. Heterojunction planar waveguide optical amplifier manufacturing method comprising a. The method of claim 6, The process of manufacturing the amplifying optical waveguide device, Forming a thin metal film having a predetermined thickness by thermal evaporation on phosphate glass to which Er ions and Yb ions are added together; After the waveguide pattern is formed through photolithography and wet etching, it is impregnated with molten KNO ₃ salt for a predetermined time to exchange Na ions of phosphate glass with K ions to form a waveguide, and then the metal thin film is removed with an acid solution. Heterojunction planar waveguide optical amplifier manufacturing method comprising a. The method according to any one of claims 6 to 9, The process of combining the two optical waveguide elements, Forming an exposed portion through photolithography and etching on the upper clad layer of the low loss optical waveguide device; After precisely processing the already prepared amplifying optical waveguide device to make an appropriate size, apply ultraviolet curing epoxy to attach to the exposed part, and the position of the optical amplifying waveguide device is fine so that the loss of signal light is minimized by injecting the signal light Adjusting; The method of manufacturing a heterojunction planar waveguide type optical amplifier comprising the step of bonding the two optical waveguide device by curing the epoxy by irradiation with ultraviolet light. The method according to any one of claims 6 to 9, The process of combining the two optical waveguide elements, And uniformly applying a refractive index matching liquid having a predetermined refractive index on the upper end of the low loss waveguide device, and then placing the optical amplification waveguide device on the light amplifying waveguide device and coupling the spring to a pre-made spring. Forming a buffer layer and a core layer having a predetermined refractive index difference by using flame hydrolysis on a silicon substrate; Forming a metal mask having a predetermined thickness through thermal deposition on the core layer, and then forming waveguide patterns of wavelength multiplexers and functional passive devices to be integrated through photolithography and wet etching; And removing the metal film after forming the wavelength multiplexer and the functional passive elements through inductively coupled plasma etching, and forming an upper clad layer using the flame hydrolysis method thereon. Manufacturing a device; Thermally depositing a thin metal film having a predetermined thickness on the silicate or phosphate glass containing Er ions or Er ions and Yb ions; After the waveguide pattern is formed through photolithography and wet etching, it is impregnated with molten KNO ₃ salt for a predetermined time to exchange Na ions of silicate or phosphate glass with K ions to form a waveguide, and then the metal thin film is removed with an acid solution. A step of manufacturing an amplifying optical waveguide device composed of a waveguide containing rare earth metal ions comprising the step of; And Positioning the amplifying optical waveguide element on top of the low-loss waveguide of the low-loss optical waveguide element, and combining the two optical waveguide elements such that a part of the rare earth metal ion-containing waveguide overlaps the upper portion of the low-loss waveguide. Heterojunction planar waveguide optical amplifier manufacturing method comprising a functional passive element characterized in that.