KR20010002707A - Tunable Wavelengh Filter Using Grating-Assisted Coupler in Electro-Optic Polymer - Google Patents

Abstract

PURPOSE: A wavelength variable optical filter for grating sub-coupler using an electro-optic polymer is provided to have the electro-optic effect by adding a dye molecule into a polymer having the high optical characteristic. CONSTITUTION: A lower electrode(210) is formed by depositing a metal on a substrate(200). A grating(220) is produced after spin-coating a low cladding layer(215). An Au mask(230) is produced with a standard lithography process after spin-coating an electro-optic polymer core layer(225). An electro-optic polymer optical path(235) is formed by etching the core layer(225). A passive polymer core layer(240) is produced by spin-coating. A photoresist mask(245) is produced with the standard lithography process. A passive polymer optical path(250) is formed by etching the core layer(240). The photoresist and the Au are removed. An upper cladding layer(255) is formed by spin-coating. An upper electrode(260) is produced and polled. A driving electrode(265) is formed by arranging patterns of the optical path(235) and an electrode mask. A section is polished to combine input beam.

Description

Tunable Wavelengh Filter Using Grating-Assisted Coupler in Electro-Optic Polymer}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lattice-assisted coupler-type wavelength tunable optical filter for use in optical division of wavelength division multiplexing. In particular, the present invention relates to a high speed variable center wavelength using an electro-optic effect induced in an electro-optic polymer. And a grating assist coupler structure consisting of an electro-optic polymer optical waveguide and a passive polymer optical waveguide.

Recently, researches on optical communication systems have been actively conducted worldwide to build a high-speed broadband integrated communication network capable of integrating various types of information such as voice, data, and video, and transmitting and processing them at high speed.

In particular, in the wavelength division multiplexing optical communication system, different information is input to multiple light sources having different wavelengths and then multiplexed and transmitted through a single optical fiber, and the receiving end demultiplexes the multiplexed signal. It is characterized in that the bandwidth of information that can be processed can be greatly increased by receiving an optical signal for each wavelength after demultiplexing. Therefore, the wavelength division multiplexing technique is known as a core technology for constructing a high speed optical communication network.

In such a wavelength division multiplexing optical communication system, in order to demultiplex the multiplexed signal and select a desired channel, a tunable wavelench filter that can be connected to a single mode fiber is required. There is a need for a fast variable wavelength optical filter of less than or equal to.

1 is a schematic block diagram showing the function of a tunable optical filter.

As shown in FIG. 1, only one channel that matches the center wavelength λ ₁ of the tunable optical filter 10 among the various channels having different wavelengths of the input terminal appears at the output terminal of the photodetector 20 side.

In order to implement the above technique, in particular, in order to tune at a high speed of ㎲ or less, it is advantageous to manufacture an element using an electro-optic effect. That is, the device using the electro-optic effect generally has a fast operating speed of about several kilowatts.

In order to achieve the above object, a tunable filter using an electro-optic effect has been mainly manufactured using a ferroelectric such as LiNbO ₃ .

In order to achieve the above object, a wavelength variable filter using an electro-optic effect has been manufactured using a ferroelectric such as LiNbO ₃ .

The wavelength variable filter using LiNbO ₃ has been patented by US Patent US4390236 (Tunable polariqation independent wavelength filter).

In the above-described invention, a wavelength tunable optical filter that can vary the center wavelength and employs a polarization selective coupler that separates a TM mode and a TE mode at an input terminal is disclosed.

Referring to the technical features of the present invention, the input light is separated into the TE mode and the TM mode by the polarization selector of the input stage, and proceeds along the TE mode path and the TM mode path, respectively. First, the wavelength selective mode converter located in the TE mode path converts the TE mode to the TM mode at a specific wavelength. Likewise, the wavelength selective mode converter located in the TE mode path converts the TM mode to the TE mode at a specific wavelength. The polarization selective coupler of the output stage combines the light energy of the TE mode and the TM mode in a single wavelength in a single path, and as a result, it is possible to fabricate a tunable optical filter that operates irrespective of polarization.

However, the LiNbO tunable optical filter is fabricated using a ₃ is a LiNbO ₃ is relatively expensive, and also suitable for the use as a large-scale in the optical network, because due to limitations of the substrate is difficult to integrate those multiple optical devices on a single substrate There is a problem that is not.

The present invention is to solve the problems of the prior art, an object of the present invention is to add a dye (dye) molecules to the polymer having excellent optical properties such as PMMA, polyimide, etc. Disclosed is a tunable optical filter using an optical polymer and a method of manufacturing the same.

In order to achieve the object of the present invention, the optical device of the present invention has a structure in which a buried electro-optic polymer optical waveguide and a buried passive polymer optical waveguide are arranged side by side, the buried electro-optic polymer optical waveguide It is proposed that the grating is configured to cause power coupling between the two waveguides at the wavelength, and the center wavelength is constructed using the electro-optic effect induced in the electro-optic polymer optical waveguide by applying a voltage to the tuning electrode.

In addition, in the technical idea of the manufacturing method of the present invention, after depositing a metal as a lower electrode formed on the substrate, and then spin-coating a lower cladding layer (top) to produce a grating in a suitable position. After the lattice is manufactured, the electro-optic polymer core layer is spin-coated. After the above process, an Au mask is formed and a reactive ion etching process is introduced to etch the core layer to form a buried optical waveguide. The passive polymer core layer is spin-coated to produce a photoresist mask on the place where the passive polymer optical waveguide is to be formed, and then a reactive ion etching process is introduced to form a buried passive polymer optical waveguide. After that, the photoresist and Au used as masks for the reaction ion etching are removed. After the treatment, the upper cladding layer is formed by spin coating thereon, and the upper electrode is manufactured by the same method as the lower electrode. In addition, electric field polling is performed to induce an electro-optic effect on the electro-optic polymer, the electro-optic optical waveguide pattern and the electrode mask pattern are aligned to form a driving electrode, and finally, a cross-section is polished to combine the input light. Thus, the manufacture of the tunable optical filter using the electro-optic polymer of the present invention can be completed.

1 is a schematic configuration diagram for explaining the function of a tunable optical filter.

2 is a block diagram of a grating assist coupler type tunable optical filter using an electro-optic polymer as an embodiment of the present invention.

3 is a schematic explanatory diagram of a manufacturing process of the tunable optical filter of FIG. 2.

4 is a transmission characteristic diagram according to the wavelength of the device for an embodiment of the present invention.

<Description of main parts of drawing>

10: wavelength tunable optical filter 20: photodetector

100: cladding layer 110: passive polymer optical waveguide

120: tuning electrode 130: electro-optic polymer optical waveguide

140: grid 150: ground

200: substrate 210: lower electrode

215: lower cladding layer 220: grating

225: electro-optic polymer core layer 230: Au mask

235: electro-optic polymer optical waveguide 240: passive polymer core layer

245 photoresist mask 250 passive polymer optical waveguide

255: upper cladding layer 260: upper electrode

265: driving electrode

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

Before describing the embodiments of the present invention, the characteristics of the electro-optic polymer will be briefly described in order to facilitate understanding of the present invention. Electro-optic polymer is manufactured to have an electro-optic effect by adding a dye molecule to a polymer having excellent optical properties such as PMMA and polyimide, and has the following excellent properties.

First, since the dielectric constant (Dielectric constsnt) is small, the speed matching between the light wave and the microwave is good, so it can be easily applied to an optical device requiring a large bandwidth.

Second, since the manufacturing process is simple, it is advantageous to manufacture low-cost devices through mass production.

Third, since there is no substrate limitation, when using a Si or GaAs substrate, an electric circuit and an optical waveguide device can be integrated together on the same substrate.

Fourth, it is easy to implement a new type of device because of its flexibility in designing the device.

In addition, in the case of an electro-optic polymer, a new pigment molecule can be studied to improve the nonlinear effect of the polymer, thereby realizing a polymer having better electro-optic properties. It is possible to prepare.

2 is a schematic configuration diagram of an embodiment of a grating assist coupler type tunable optical filter using the electro-optic polymer of the present invention.

As shown in FIG. 2, an electro-optic polymer optical waveguide having a longitudinal direction at a predetermined position inside the upper and lower cladding layers 100 formed on a substrate (not shown), and having a plurality of gratings 140 formed thereon. 130, a passive polymer optical waveguide 110 spaced apart from the electro-optic polymer optical waveguide 130 by a predetermined distance in a longitudinal direction inside the cladding layer 100, and a bottom of the bottom cladding layer 100. A ground portion 150 formed in the same direction as the electro-optic polymer optical waveguide 130 and a tuning electrode 120 formed on the upper cladding layer 100 in the same direction as the electro-optic polymer optical waveguide 130. It is composed.

The tuning electrode 120 is for varying the center wavelength, the grating 140 is between the electro-optic polymer optical waveguide 130 and the passive polymer optical waveguide 110 buried in the cladding layer 100 at a specific wavelength. It is for generating a power coupling.

In the embodiment of the present invention, the two waveguides 110 (the two by the grating 140 in the input light multiplexed into the input terminal of the passive polymer optical waveguide 110 embedded in the cladding layer 100 multiplexed) Only signals of wavelengths where the phase matching conditions between 130 are satisfied are coupled to the embedded electro-optic polymer optical waveguide 130.

In addition, only one specific wavelength is coupled to the embedded passive polymer optical waveguide 110 even for input light multiplexed by multiple wavelengths incident on the embedded electro-optical optical waveguide 130. In this case, when the coupling between the two waveguides 110 and 130 is weak, the lattice period may be determined from the following phase matching condition.

β ₁ -β ₂ = 2π / Λ

Here, β ₁ and β ₂ are propagation constants of the two waveguides 110 and 130, respectively, and Λ is a period of the grating 140.

Hereinafter, a process of manufacturing the tunable optical filter using the electro-optic polymer of the present invention will be described in detail with reference to the accompanying drawings.

3 is for explaining a process of manufacturing a tunable optical filter using the electro-optic polymer of the embodiment of the present invention. The process of manufacturing the tunable optical filter using the electro-optic polymer of the present invention includes the following processes.

(A) forming a lower electrode 210 by depositing a metal on the substrate 200, and (Fig. 3 (a))

(b) after the step (a), spin-coating the lower cladding layer 215 thereon, and then fabricating the grating 220 at a predetermined position (FIG. 3). (b))

(c) After the step (b), spin coating the electro-optic polymer core layer 225 thereon, and then fabricating the Au mask 230 on the place where the optical waveguide is to be formed using a standard lithography process. Process to do, (FIG. 3 (c))

(d) After the step (c), a reaction ion etching (O ₂ RIE) process by oxygen plasma is introduced to etch all the electro-optic polymer core layers 225 to form a buried electro-optic polymer optical waveguide 235. And spin-coating the passive polymer core layer 240 thereon, and fabricating the photoresist mask 245 on the place where the passive polymer optical waveguide is to be formed using a standard lithography process, (FIG. 3 ( d))

(e) After the above step (d), the passive polymer core layer 240 is etched by etching all of the passive polymer core layers 240 by the reactive ion etching process by oxygen plasma, and the reactive ion etching process is performed by using a mask. A process of removing the photoresist and Au used, (FIG. 3 (e))

(f) after the step (e), the upper cladding layer 255 is formed thereon by spin coating, and the upper electrode 260 is manufactured by the same method as the lower electrode 210, and then the electro-optic polymer is Performing a polling to cause an optical effect, and (FIG. 3 (f))

(g) After the step (f), the electro-optic polymer optical waveguide 235 pattern and the electrode mask pattern are aligned to form the driving electrode 265, and finally, the cross section is polished to couple the input light. Process to do. (Fig.3 (g))

Figure 4 is a numerical value of the change in the transmission characteristics according to the wavelength of the tunable optical filter according to an embodiment of the present invention using the effective index method and the beam propagation method to verify the effect of the present invention The simulated results are shown.

Figure 4 (a) shows a simplified structure of the device of the present invention performing numerical simulation. Here, n ₁ , n ₃ , n ₅ correspond to the cladding layer, n ₂ represents a passive polymer optical waveguide, and n ₄ represents an electro-optic polymer optical waveguide. In addition, d ₂ is the thickness of the passive polymer optical waveguide, d ₄ is the thickness of the electro-optic polymer optical waveguide, D _gr is the thickness of the grating, 2S ₃ is the distance between the two optical waveguides.

4 (b) and 4 (c) show the transfer characteristics when the distance 2S ₃ between the two waveguides is 6 µm and 8 µm, respectively.

In both cases, the center wavelength of the filter is located at 1.55 mu m. When the spacing between the two waveguides (2S ₃ ) is 6 μm (FIG. 4 (b), the coupling length becomes about 346 times the grating period and the full width half maximum (FWHM) is about 2.4 nm). When the spacing between the two waveguides is 8 µm (Fig. 4 (c)), the bond length is longer, which is about 933 times the lattice period, and the FWHM is about 0.8 nm. By adjusting the coupling length using, we can design a frequent optical filter with the desired bandwidth.

While one embodiment of the present invention has been described above, various embodiments of the present invention may be embodied as long as the average expert in the art includes the present invention.

As described above, the present invention relates to a lattice-assisted coupler-type wave tunable optical filter manufactured by using an electro-optic polymer, and is used to select a signal of a desired channel in an optical communication system of wavelength division multiplexing. Since the center wavelength can be changed at high speed by using the electro-optic effect which is induced in, it is advantageous to implement the optical packet switching function.

By securing the technology of integrating the electro-optic polymer optical waveguide and the passive polymer optical waveguide, it is possible to implement a variety of polymer optical waveguide devices.

Claims (9)

In the grating assist coupler type wavelength tunable optical filter used for optical division of wavelength division multiplexing, An electro-optic polymer optical waveguide buried in the cladding layer, A buried passive polymer optical waveguide arranged at a position spaced apart from the electro-optic polymer optical waveguide by a predetermined distance; A lattice formed in the embedded electro-optic polymer optical waveguide or in the embedded passive polymer optical waveguide, Comprising a tuning electrode formed on the cladding layer above, The grating acts to cause power coupling between the two waveguides at a particular wavelength and to vary the center wavelength using an electro-optic effect induced in the electro-optic polymer optical waveguide by applying a voltage to the tuning electrode. Wavelength Tunable Optical Filter for Lattice-assisted Coupler Using Electro-optic Polymer The tunable optical filter of claim 1, wherein the electro-optic polymer optical waveguide and the passive polymer optical waveguide are arranged in a form buried side by side in the longitudinal direction of the cladding layer. The tunable optical filter for grating auxiliary coupler using an electro-optic polymer according to claim 1, wherein the grating is formed on a bottom surface of the electro-optic polymer optical waveguide. The tunable optical filter for grating auxiliary coupler using an electro-optic polymer according to claim 1, wherein the grating is formed on the bottom of the passive polymer optical waveguide. The wavelength tunable optical filter of claim 1, wherein the tuning electrode is formed so that the electric field and the light wave overlap well in the electro-optic polymer optical waveguide. The tunable optical filter of claim 1, wherein the electro-optic polymer is prepared by adding a dye molecule to a polymer having excellent optical properties such as PMMA or polyimide. The buried electro-optic according to claim 1, wherein only signals having a wavelength satisfying a phase matching condition between the two waveguides by the grating in the input light multiplexed into the input terminal of the passive polymer optical waveguide embedded in the cladding layer are multiplexed. Wavelength variable optical filter for grating auxiliary coupler using an electro-optic polymer characterized in that the output is coupled to the polymer optical waveguide The method according to claim 1, wherein only one specific wavelength is coupled to the buried passive polymer optical waveguide for the multiplexed input light multiplexed to the buried electro-optical optical waveguide using the electro-optic polymer Tunable Optical Filters for Lattice Auxiliary Combiners A method for manufacturing a lattice assisted coupler type wavelength tunable optical filter using an electro-optic polymer used for wavelength division multiplexing optical communication, the manufacturing method comprising the following steps: grating assist using an electro-optic polymer Method of manufacturing a combiner type tunable optical filter (a) forming a lower electrode by depositing a metal on the substrate; (b) after the step (a), spin coating the lower cladding layer thereon, and then manufacturing a lattice at a predetermined position. (c) after the step (b), spin coating an electro-optic polymer core layer thereon, and then fabricating an Au mask on the place where the optical waveguide is to be formed using a standard lithography process. (d) After the step (c), a reaction ion etching (O ₂ RIE) process by oxygen plasma is introduced to etch all the electro-optic polymer core layers to form a buried electro-optic polymer optical waveguide, on which a passive polymer core is formed. Fabrication of spin-coated layers and fabrication of photoresist masks on top of passive polymer optical waveguides using standard lithography processes (e) After the above step (d), the passive polymer core waveguide is formed by etching all the passive polymer core layers by the reactive ion etching process by oxygen plasma, and the photoresist and Au used as a mask when the reactive ion etching is performed. Process to remove (f) after the step (e), the upper cladding layer is formed thereon by spin coating, the upper electrode is fabricated in the same manner as the lower electrode, and then polled to induce an electro-optic effect on the electro-optic polymer. Process to perform (g) after the step (f), aligning the electro-optic polymer optical waveguide pattern and the electrode mask pattern to form a driving electrode, and finally polishing the cross section to couple the input light.