KR100293317B1 - Electro-optic polymer optical waveguide polarization-independent light modulator and its manufacturing method - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-optic polymer optical waveguide and a polarization independent optical modulator, and a method of fabricating the same. It is manufactured by reactive ion etching process and inputs by connecting two kinds of electrodes of the same length in series so that the optical axis of the optical waveguide can be formed 45 ° counterclockwise and 45 ° clockwise with respect to the substrate surface through the electric field polling process. By devising an electro-optic polymer optical phase modulator that operates independently of the polarization state of light and such an optical phase modulator on both waveguides of the Mach-Zehnder interferometer, by devising an electro-optic polymer light intensity modulator that operates independently of the polarization state of the input light, As the need for a high speed light modulator without polarization dependence increases, polarization such as the present invention The demand of the independent electro-optic optical phase modulator or the light intensity modulator is greatly increased, and the electrode structure proposed in the present invention can be designed with a traveling waveform, which is advantageous in manufacturing a high speed optical modulator.

Description

Electro-optic polymer optical waveguide polarization independent optical modulator and manufacturing method thereof

The present invention relates to an electro-optic polymer optical waveguide polarization independent light modulator using 45 ° electric field polling and a method of fabricating the same.

To date, polarized independent electro-optic optical modulators have been proposed and manufactured using LiNbO ₃ , semiconductors, and the like.

Recently, as the research into the device using the electro-optic polymer is actively conducted, an electro-optic optical modulator that operates irrespective of polarization has been proposed by appropriately designing an electric poling electrode structure.

On the other hand, in the prior patent, "Polarization-insensitive linear waveguide electrooptic phase modulator [Patent No. US Patent 4932737]" polarization by making two sets of electrodes that can apply the electric field in the horizontal and vertical direction to the electro-optic polymer optical waveguide An independent electro-optic optical phase modulator was designed.

However, the prior patent has not been easy to design the electrode as a traveling waveform because the electrode is divided into two parts.

Therefore, there is a problem in that it is difficult to manufacture a high speed optical phase modulator.

Also, the preceding paper IEEE Photonics Technology, Vol. 8, No. 11, Nov. 1996, pp. In "Polymeric polarization-independent modulator incorporating twisted optic-axis waveguide polarization converters" of 1483-1485, a polarization-independent electro-optic light intensity modulator was designed by sequentially connecting a phase modulator, a polarization converter, and a phase modulator to an electro-optic polymer optical waveguide. .

However, in the above paper, the characteristics of the entire device depend largely on the characteristics of the polarization transducer, and the insertion of the device lengthens the device.

In addition, since the electrodes of the phase modulator and the polarization transducer are separated, the design of the traveling waveform electrode is not easy, and thus, there is a problem that the high speed light intensity modulation is not suitable.

An optical waveguide type electro-optic optical modulator is an element that changes the phase or intensity of light exiting the output by applying an electric field to modulate the light incident to the input of the optical waveguide, which is essential in a high speed optical communication system.

Electro-optic light modulation utilizes an electrooptic effect in which the optical refractive index changes with the electric field, which depends on the polarization state of the light.

In general, it is an elliptical polarization that is emitted from a laser and propagates an optical fiber and is coupled to an optical modulator.

When the light is incident on the optical waveguide of the electro-optic optical modulator, both the transverse electric (hereinafter referred to as TE) and the transverse magnetic (hereinafter referred to as TM) modes can be excited.

Therefore, there is a need for an electro-optic light modulator that operates without depending on the polarization of the input light.

The present invention has been made to solve the above problems, and an object thereof is to provide an optical waveguide type electro-optic optical modulator having the same output irrespective of the polarization state of the input light.

1 is a schematic structural diagram of a polarization independent electro-optic polymer optical phase modulator to which the present invention is applied.

FIG. 2 is a sectional view taken along the lines A1-A2 and B1-B2 of FIG.

3 is a schematic structural diagram of a polarization independent electro-optic polymer light intensity modulator according to the present invention.

* Explanation of symbols for main parts of the drawings

100, 113, 123: substrate surface

110, 120: Electrode for electric field poly in A, B area

111, 121: cladding layer

111a, 121a: upper electrode

111b, 121b: core layer

111c, 121c: lower electrode

112, 122: insulating layer

130: waveguide

In order to achieve the above object, the electro-optic polymer optical waveguide according to the Bono polarization independent optical phase modulator includes a channel type optical waveguide for guiding both the transverse electric (TE) and the transverse magnetic (TM) modes using an electro-optic polymer. The optical axis of the channel-type optical waveguide is formed at a counterclockwise direction in some regions of the channel-type optical waveguide with respect to the substrate surface and in a clockwise direction in the other regions so that the optical axes in the two regions are perpendicular to each other. It is characterized by the fact that two kinds of electrodes having the same length are composed of electrodes for electric field poly connected in series so as to perform the same phase change regardless of the polarization state.

In addition, the electro-optic polymer optical waveguide polarization independent optical light modulator according to the present invention is a Mach-Zehnder interferometer consisting of a channel-type optical waveguide for guiding both the transverse device (TE) and transverse magnetic (TM) mode with an electro-optic polymer material; The optical axis of both channel type optical waveguides is formed counterclockwise in some areas of the channel type optical waveguide and clockwise in the other areas, so that the optical axes in both areas are perpendicular to each other. In order to achieve the same intensity change regardless of the polarization state of the input light, two types of electrodes having the same length are configured as electric field polling electrodes connected in series.

The change of the optical refractive index by the applied electric field is called an electro-optic effect, and this effect causes the phase change of the waveguide light.

However, this phase change depends on the polarization state of the waveguide.

This polarization dependency is caused by the phase change of the waveguide parallel to the optical axis when the electric field parallel to the optical axis is applied, but the phase change of the waveguide light of the polarization state perpendicular to the optical axis.

Therefore, in the present invention, when two optical waveguides in which the optical axes are perpendicular to each other are connected in series to apply a full length parallel to the optical axis of each optical waveguide, the waveguide light sequentially passes through the two regions and finally the same regardless of the polarization state of the input light. In view of the fact that it undergoes phase change, a channel optical waveguide that guides TE and TM modes in the same manner using an electro-optic polymer is fabricated by an oxygen reactive ion etching process, and an oxygen reactive ion etching of an optical waveguide through an electric field polling process. The optical axis of the optical waveguide can be formed at 45 ° counterclockwise and 45 ° clockwise with respect to the substrate surface through the electric field polling process. We devise an electro-optic polymer optical phase modulator that operates regardless of polarization state.

In order to obtain an electro-optic effect, the electro-optic polymer undergoes an electric field polling process, in which the optical axis is the same as the electric field.

Since the optical waveguide having the optical axis in the desired direction can be formed according to the electrode position required for the electric field poly, it is possible to fabricate the polarization independent electro-optic polymer optical phase modulator and the light intensity modulator designed in the present invention.

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

1 is a schematic structural diagram of a polarization-independent electro-optic polymer optical phase modulator to which the present invention is applied. The optical axis of the optical waveguide above and below the channel optical waveguide is 45 ° counterclockwise with respect to the substrate surface and 45 in a clockwise direction. The electrodes 110 and 120 for Wuhan electric field poly are placed.

The electrodes 110 and 120 are used for modulation after fabricating the device.

The electrodes 110 and 120 have a structure for making the phase change equal to the same modulation voltage irrespective of the polarization of the waveguide light.

As shown in FIG. 1, the electrodes 110 and 120 are composed of two regions (region A and region B), in which region A has an optical axis of the waveguide 45 ° counterclockwise with respect to the substrate surface 100 and region B 45 ° clockwise. The length of the two regions is the same as L, if the structure is to be made into.

Therefore, the optical axes in the two regions are perpendicular to each other.

Although there can be various electrode structures in which two optical waveguides connected in series are perpendicular to each other, the present invention is designed as a structure for forming a 45 ° optical axis.

In this case, since the regions A and B of the electrodes 110 and 120 above and below the optical waveguide 130 are connected, they may be used as traveling wave electrodes for high speed modulation.

FIG. 2 is a cross-sectional view taken along the lines A1-A2 and B1-B2 of FIG. 1, wherein the distance between the electrodes 110 and 120 on the optical waveguide and the electrodes on the optical waveguide is counterclockwise with respect to the substrate surface. This is an important parameter for making 45 ° clockwise or 45 ° clockwise.

Figure 3 shows the structure of the optical waveguide type flat tube independent electro-optic polymer light intensity modulator proposed in the present invention.

The optical waveguide 130 is in the form of a Mach-Zehnder interferometer, and both optical waveguides are composed of optical waveguide-type polarization independent electro-optic optical phase modulators proposed in the present invention.

When the waveguide light incident on the input of the Mach-Zehnder interferometer is divided in half in the Y-type optical splitter and the phase difference of the light passing through both optical waveguides is 180 °, the light is canceled by the Y-type optical coupler and the output light is not emitted. If there is no difference, they are combined in the Y-type optical coupler so that the intensity of the output light is equal to the intensity of the input light.

Since the polarization independent electro-optic optical phase modulator of the present invention is used for both optical waveguides, the waveguide light passing through each waveguide undergoes the same phase change regardless of the polarization state with respect to the same modulation voltage.

In this case, since the electrodes 110 and 120 above and below the optical waveguide are connected from the beginning to the end, they can be used as traveling wave electrodes for high speed optical intensity modulation.

The modulator proposed in the present invention has the following advantages over the conventionally proposed polarization independent electro-optic polymer optical modulator.

First, since the electrode can be designed with a traveling waveform, it can be applied as a high speed modulator.

Second, the electrode structure is simple, the length can be shortened.

Referring to Figure 2, a schematic manufacturing process of the proposed device in this invention, by first depositing a crystalline substrate (substrate) metal above (113 123) of the insulators, etc. (insulator) (112,122) have raised the silicon, such as SiO ₂ This is patterned to form lower electrode for electric poling 111c and 122c.

An appropriate polymer is spin coated to form a lower cladding layer and core layers 111b and 121b with electro-optic polymers.

Next, an upper cladding layer is formed, and metal is deposited thereon to be patterned to form upper electrode for electric poling 111a and 121a.

Thereafter, the electric field polling is performed properly so that the electro-optic polymer has the electro-optic effect and the 45 ° / -45 ° optical axis, and the electrode used for the electric field polling is used as a modulating electrode as it is.

As described above, the expected effects of the electrooptic polymer optical waveguide polarization independent optical modulator of the present invention are as follows.

As the need for an electro-optic light intensity modulator without polarization dependence increases, the demand for a polarization free electro-optic light intensity modulator such as the present invention will increase greatly.

In addition, the electrode structure devised in the present invention can be designed with a traveling waveform, which is advantageous for manufacturing a high speed light modulator.

Claims (5)

A channel type optical waveguide for guiding both the transverse electric (TE) and transverse magnetic (TM) modes using an electro-optic polymer as a material; The optical axis of the channel-type optical waveguide is formed counterclockwise in some regions of the channel-type optical waveguide with respect to the substrate surface, and a 45 ° angle is formed clockwise in the remaining regions so that the optical axes in the two regions are perpendicular to each other. Electro-optic polymer optical waveguide polarization independent optical phase modulator, characterized in that consisting of a full-pole polling electrode in which two kinds of electrodes of the same length are connected in series so as to perform the same phase change to the polarization state of the input light. A Mach-Zehnder interferometer comprising a channel type optical waveguide for guiding both the transverse electric (TE) and transverse magnetic (TM) modes using an electro-optic polymer as a material; The optical axes of both the channel-type optical waveguides of the Mach-Zehnder interferometer are formed counterclockwise in some regions of the channel-type optical waveguide and clockwise in the remaining regions, and the optical axes in the two regions are mutually Electro-optic polymer optical waveguide polarization independent light intensity modulator characterized in that it consists of a full-pole polling electrode in which two kinds of electrodes of the same length are connected in series to achieve the same intensity change irrespective of the polarization state of the input light to form a vertical . A first step of fabricating a channel-type optical waveguide made of an electro-optic polymer material that equally guides the transverse device (TE) and transverse magnetic (TM) modes in an oxygen reactive ion etching process; The optical axis of the electro-optic polymer optical waveguide is formed counterclockwise in some regions of the channel-type optical waveguide and clockwise in the remaining regions by using an electric field polling process to form an optical axis in both regions. An electro-optic polymer optical waveguide comprising a second process of designing and manufacturing a polling electrode formed by connecting two kinds of electrodes having the same length in series so as to be perpendicular to each other so as to operate regardless of the polarization state of the input light. Method of manufacturing a polarization independent optical modulator. The method of claim 3, wherein the first process is Depositing and patterning a metal on the crystalline substrate of silicon on which the insulator is raised to form a lower electric field falling electrode; Forming a lower cladding layer by spin coating a polymer after forming a lower electric field falling electrode and forming a core layer from an electro-optic polymer; A method of fabricating an electro-optic polymer optical waveguide single-gap independent optical modulator, comprising a third step of forming a channel waveguide by performing a reaction ion etching process after forming a core layer. The method of claim 3, wherein the second process is A first step of depositing a metal on the cladding layer after forming the upper cladding layer and forming the upper electric field falling electrode by patterning the metal; Performing a full length polling so that the electro-optic polymer has an electro-optic effect and a 45 ° / -45 ° optical axis; And a third step of using the electrode used for the electric field polling as a modulating electrode as it is.