KR100281736B1 - Structure and fabrication method of wye-branch type optical waveguide polarized light separator - Google Patents

Abstract

The present invention relates to a structure and a fabrication method of a Y-branch type optical waveguide polarized light separator using a polymer having a large optical birefringence, and more particularly, to a polymer optical waveguide lower cladding layer formed on an arbitrary substrate, TE and TM polarized light components are all guided by the TE and TM polarized light components; a branch in which a TE polarized light component is guided by mode evolution by inserting a birefringent optical polymer layer into one branch of the Y-branch polymer optical waveguide; A Y-branch polymer optical waveguide core layer consisting of a different branch such that the insertion of the birefringent optical polymer layer into the branch polymer optical waveguide branches is removed so that the TM polarization component due to the increase of the relative effective refractive index of the TM mode is guided by mode evolution; And a polymer optical waveguide upper cladding layer formed on the upper surface of the optical waveguide, Forming a polymer layer having a refractive index lower than that of a silicon layer or a core layer polymer as a cladding layer; forming a birefringent optical polymer layer having a large birefringence on the lower cladding layer and performing photolithography and ion etching (RIE) Leaving only one branch of the Y-branch type optical waveguide; flattening the upper part by coating an optical waveguide core material on the lower cladding layer and the birefringent optical polymer layer; A step of aligning the optical waveguide mask and forming an optical waveguide shape by using photolithography, a step of etching the region excluding the central portion of the optical waveguide by reactive ion etching (RIE) after forming the optical waveguide shape, By performing the step of coating the polymer for the cladding layer to complete the device, the polarization separation ratio is high, And can be manufactured in a wide range of polarization-related systems in the future, and can be integrated with polymer optical waveguide devices to provide a new type It is possible to fabricate an optical waveguide device.

Description

Structure and fabrication method of wye-branch type optical waveguide polarized light separator

The present invention can be fabricated by integrating a polymer having optical birefringence on a part of a Y-branch type optical waveguide, and a structure of a new type of polymer optical waveguide polarized light separator using a mode evolution principle. And a manufacturing method thereof.

A technique related to a conventional integrated optical waveguide polarization separation element is as follows.

First, US Pat. No. 5,056,883 (MBJ Diameer et al., Field at Jan. 25, 1991) selectively poles only one branch in a Y-branch type optical waveguide fabricated using a nonlinear polymer optical waveguide, Patent, and IEEE Electron, Lett., Vol. 32, No. 4, pp. 324-325 (1996) (M.C. Oh et al.), In a Y-branch type optical waveguide fabricated by using a nonlinear polymer optical waveguide, the optical birefringence is selectively excited by selectively poling only one branch portion And a polarized light separator is fabricated.

IEEE Photon. Technol. (P.-K.Wei et al.), In which a plurality of kinds of elements are internally diffused into a lithium niobate substrate, Discloses that a polarized light separator is manufactured using birefringence and a Y-branch type optical waveguide.

Next, IEEE Photon. Lett., Vol. 5, No. 9. pp. 1047-1049 (1993) (F. Ghirardi et al.,) Fabricated a directional coupler optical waveguide on an indium phosphide (InP) substrate and fabricated a polarized light separator using the coupling distance difference according to polarization. And IEEE I. Lightwave Technol., Vol. 12, No. 4, pp. 625-633 (1994) (M. Okuno et al.), Disclose the production of a polarized light separator by controlling the birefringence by applying a laser to the optical waveguide device using silica to apply stress.

The conventional polymer optical waveguide polariser is fabricated by using birefringence according to poling in a nonlinear polymer, and it is difficult to apply appropriate birefringence by only polling a specific portion. Also, due to a large absorption loss of a nonlinear polymer and an increase in loss due to polling There is a disadvantage in that the insertion loss of the fabricated device is relatively large and a difference is generated depending on the polarization.

It is an object of the present invention to provide a new type of polymer optical waveguide polarized light separator which can be fabricated more easily than conventional optical waveguide devices, has a small loss, and has a high polarization separation ratio.

In order to attain the above object, the present invention provides a polarization beam splitter comprising: a polymer optical waveguide lower cladding layer formed on an arbitrary substrate; an input portion through which TE and TM polarized light components of both TE and TM polarized light components of the input light are guided; Branching optical polymer layer is inserted into one branch of the waveguide so that the TE polarized light component is guided by the mode evolution and the insertion of the birefringent optical polymer layer into the other branch of the Y-branch polymer optical waveguide is removed to increase the relative effective refractive index And a polymer optical waveguide upper cladding layer formed on the optical waveguide by coating the Y-branch polymer optical waveguide core layer and the polymer optical waveguide upper cladding layer.

According to another aspect of the present invention, there is provided a method for fabricating an optical waveguide, comprising: forming a polymer layer having a lower refractive index than a silicon layer or a core layer polymer as a lower cladding layer of an optical waveguide on a substrate; (RIE) so as to remain on only one side of the Y-branch type optical waveguide; forming an upper portion of the optical waveguide core material on the lower cladding layer and the birefringent optical polymer layer, Forming an optical waveguide shape by using a photolithography; forming a light waveguide shape by reactive ion etching (RIE); forming a light waveguide shape on the planar birefringent optical polymer; Etching the region except for the central portion of the waveguide, and coating the polymer for the upper cladding layer after etching And in that it comprises the step of finish cut with a further feature.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a Y-branch type polymer optical waveguide polarized light separator using a birefringent polymer to which the present invention is applied.

FIG. 2 is a characteristic diagram of an effective refractive index distribution for TE and TM polarized light according to the present invention. FIG.

3A to 3C are views showing a process for producing a polymer optical waveguide polarized light separator according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

1: birefringence optical polymer

2: Y-branch polymer optical waveguide core layer

3: polymer optical waveguide lower cladding

4: Polymer optical waveguide upper cladding

5: Silicon (Si) substrate

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

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of a Y-branch type polymer optical waveguide polarized light separator using a birefringent polymer to which the present invention is applied.

A polymer lower cladding layer 3 formed on an arbitrary substrate and a birefringent optical polymer 1 formed only on an area corresponding to one arm of the Y-branch type optical waveguide on the lower cladding layer 3 , A Y-branch polymer optical waveguide core layer (2) formed on the lower cladding layer (3) and the birefringent optical polymer (1), and a polymer optical waveguide upper cladding layer (4) formed by coating on the optical waveguide do. In general, the birefringence optical polymer has a large refractive index difference of about 10 ^-2 between the TE mode and the TM mode.

1 shows the position of the birefringent polymer aligned with the optical waveguide. The birefringent optical polymer 1 has a different refractive index depending on the polarization of the optical wave. For easier explanation, It is assumed that it has a large refractive index and a small refractive index with respect to the TM polarized light.

Of course, depending on the type of polymer, the polymer may have a birefringence opposite to that, and such a polymer may also be used in the fabrication of the proposed device.

The operating characteristics of the three-dimensional optical waveguide device can be generally explained by using the effective refractive index in order to facilitate the analysis.

The effective refractive index in the case of optical birefringent medium is different depending on the polarization. In FIG. 2, the effective refractive index distribution is shown.

The effective refractive index of the right branch with birefringent optical polymer 1 is higher for TE polarized light and lower for TM polarized light. Conversely, the effective refractive index of the left branch without birefringent optical polymer is higher for TM polarized light and lower for TE polarized light.

When the light wave is incident on the asymmetric Y-branch type polymer optical waveguide core layer 2 formed as described above, the TE and TM polarized light propagates toward the branch having the higher refractive index, and the polarized light separation occurs, The TM polarized light component propagates through the branch with the birefringent polymer and the TM polarized light component propagates to the opposite branch. The performance of the polarized light separator is determined by the magnitude of the branching angle and the birefringence. When the branching angle is small and the birefringence is large The polarized light separation becomes high.

Unlike the structure of the polarized light separator described above, the birefringent polymer is aligned on both branches of the Y-type optical waveguide, and the thickness of the birefringent polymer aligned on each branch is made different so that the refractive index difference according to the two planes can be controlled You may.

3A to 3C are cross-sectional views illustrating a process of manufacturing a polymer optical waveguide polarized light separator according to the present invention. This is explained as follows.

First, a general silicon (Si) substrate is prepared for preparing a polymer device, and a SiO ₂ layer is formed as a lower cladding layer 3 of the optical waveguide on the prepared substrate or a polymer having a refractive index lower than that of the core layer polymer is coated Then, the optical polymer 1 having a large birefringence is coated on the lower cladding layer 3 so as to remain only on one branch portion of the optical waveguide.

Reactive ion etching (hereinafter referred to as RIE) may be used for this purpose. However, when the optical polymer 1 has photosensitive characteristics, a desired pattern can be formed simply by photolithography.

After the birefringent optical polymer 1 is formed, the optical waveguide core material is coated to make the top flat, the Y-branch optical waveguide mask is aligned on the flat top, and the optical waveguide shape is formed by photolithography. After fabrication, use the RIE process to deeply etch the region except the central part of the optical waveguide.

Finally, when the polymer for the upper cladding layer 4 is coated, the fabrication of the device is completed.

At this time, the cross-sectional formation for the input and output of the light wave uses a cleavage method or a polishing method using a silicon (Si) cut surface.

The thus fabricated optical waveguide polarized light separator of the present invention is much simpler to manufacture than the method using birefringence due to poling of a nonlinear polymer and does not require an electrode fabrication process or an electric field polling process.

As described above, the polarized light separator of the present invention has advantages of high polarization separation ratio, small loss, and easy fabrication. Further, since it is an element that can be mass-produced at low cost by using a polymer, it can be applied to a multi- .

Further, the optical waveguide device can be integrated with existing optical waveguide devices to produce a new type optical waveguide device.

Claims (2)

An optical waveguide TE, TM polarized light separator, comprising: a polygonal optical waveguide lower cladding layer formed on an arbitrary substrate; An input part for guiding all of the TE and TM polarized light components to the upper part of the lower cladding layer, a Y-branch polydimuth optical waveguide for introducing a birefringent optical polymer layer into one branch, And a Y-branch polymer optical waveguide configured by removing the insertion of the birefringent optical polymer layer on the other branch of the Y-branch polymer optical waveguide so that the TM polarization component due to the increase of the relative effective refractive index in the TM mode is guided by mode evolution. Core layer; And a polymer optical waveguide upper cladding layer formed by coating on the optical waveguide. A birefringent optical polymer layer formed on only one branch region of the Y-branch type optical waveguide on the lower cladding layer, and a polymer optical waveguide core layer formed on the lower cladding layer and the birefringent polymer layer, And a polymer optical waveguide upper cladding formed by coating on the optical waveguide core layer, wherein the lower cladding layer of the optical waveguide is made of a silicon layer or a core layer polymer Forming a polymer layer having a low refractive index; Forming a birefringent optical birefringent optical flat layer on the lower cladding layer and leaving only one branch of the Y-branch type optical waveguide using photolithography and ion etching (RIE); Coating the optical waveguide core material on the lower cladding layer and the birefringent optical polymer layer to flatten the upper portion; Arranging a Y-branch optical waveguide mask on top of a flat birefringent optical polymer and making an optical waveguide shape using photolithography; Etching the region excluding the central portion of the optical waveguide by reactive ion etching (RIE) after forming the optical waveguide shape; And then coating the polymer for the upper cladding layer after the etching to complete the device.

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