KR20070093285A - Microring resonator filter with variable bandwidth and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a microring resonator filter having a variable bandwidth and a manufacturing method thereof, comprising: a straight bus waveguide through which light passes; A plurality of ring waveguides spaced apart from the straight bus waveguide, the plurality of ring waveguides being coupled and resonated with a portion of the light passing through the straight bus waveguide; And a conductor for applying a voltage to each of the ring waveguides to change the refractive index of each of the ring waveguides.

Accordingly, the present invention can implement a plurality of micro ring resonators having different Q values by varying the radius of the ring resonator, by applying a voltage to the remaining conductors, except for the conductor of a specific resonator among these resonators. By shifting the center wavelength of the light, it is possible to determine the transmission characteristics of the entire device in a specific resonator in which no voltage is applied.

In addition, the present invention has the effect of controlling the Q value by using the mode cut-off voltage so that the transfer characteristics of the entire device appear only in a specific resonator among the plurality of resonators.

Description

Microring resonator filter with variable bandwidth and its manufacturing method {Microring resonator filter with variable bandwidth and method of manufacturing the same}

1 is a conceptual diagram illustrating a schematic structure of a general integrated optical microring resonator;

2a and 2b is a transfer characteristic diagram of a microring resonator as shown in FIG.

3 is an equivalent refractive index distribution diagram of the microring resonator of FIG.

4 is a schematic configuration diagram of a microring resonator filter having a variable bandwidth according to the present invention;

5 is a schematic cross-sectional view of a microring resonator filter having a variable bandwidth according to the present invention.

6 is a schematic configuration diagram of a single microring resonator according to the present invention;

7 is a schematic perspective view of a single microring resonator in accordance with the present invention;

8 is a propagation characteristic diagram of a microring resonator filter having a variable bandwidth according to the present invention.

9A and 9B are diagrams of propagation characteristics when voltage is applied to a ring resonator of a microring resonator filter having a variable bandwidth according to the present invention.

10A to 10F are schematic cross-sectional views illustrating a method of manufacturing a microring resonator filter having a variable bandwidth according to the present invention.

<Description of the symbols for the main parts of the drawings>

100,402a: straight bus waveguide 201,202,203,204,402b: ring waveguide

211,212,213,214,600: Conductor 301,302,303,304: Power

400,401,403: cladding layer 402: core layer

450: photoresist layer 480: mask

500: Substrate

The present invention relates to a microring resonator filter having a variable bandwidth and a method of manufacturing the same.

Currently, the field of optoelectronics technology combining optics and electronics continues to develop.

This optoelectronic technology is needed to develop devices that combine optical and electronic technologies, such as devices that respond to optical power, devices that emit or change light, and devices that use light for internal operation.

Recently, interest in optical system-on-chip (SoC) technology, which can implement various optoelectronics functions on a substrate, is increasing among optoelectronics technologies.

These optical SoC technologies include optical integrated circuits for next-generation high-capacity optical communication systems, intelligent robots, direction sensors and speed sensors for intelligent vehicles, non-destructive and contactless biosensors and chemical sensors in the form of lab-on-a-chip, It can be applied to implement the optical connection system for the next generation computer.

Integrated optical microring resonators, like transistors in highly integrated electronic circuits, are key devices that can be used as building blocks for optical SoCs.

1 is a conceptual diagram illustrating a schematic structure of a general integrated optical microring resonator, and includes a straight bus optical waveguide 10; It consists of a ring waveguide 20 spaced apart from the linear bus optical waveguide 10.

The device combines one straight wave waveguide with a circular ring waveguide.

First, part of the light incident to the input port of the linear optical waveguide is transmitted to the ring waveguide, and the remaining light is output to the through port.

At this time, the light transmitted to the ring waveguide accumulates while rotating the ring, and part of the light is coupled to the linear optical waveguide to cause resonance with respect to the optical wavelength.

Therefore, the microring resonator has a characteristic of a band stop filter.

That is, when light A having a constant optical power is input to the input port of the linear optical waveguide as shown in FIG. 2A, a portion of the light is coupled and resonated in the ring waveguide, and thus, the through port has the wavelength 'λ 1', 'as shown in FIG. 2B. A transmission characteristic is shown in which light B having optical powers of which? 2 'and' λ3 'are filtered is output.

Here, the radius R of the ring and the effective refractive index of the waveguide are important factors in determining the free spectral range (FSR).

In other words, the smaller the radius of the microring resonator, the wider the FSR.

In particular, since the bending loss for determining the radius of the ring is inversely proportional to the refractive index difference between the core of the waveguide and the cladding, the smaller the refractive index difference is, the larger the radius of the ring becomes and the device has a narrower FSR.

Therefore, in order to reduce the size of the device, the FSR is widely implemented using a III-V compound semiconductor or a silicon on insulator (SOI) substrate.

As a result, the scattering loss due to the etching process of the transmission loss that determines the performance of the ring resonator is proportional to the difference in refractive index, thereby degrading the performance of the device.

In addition, in order to maintain the coupling efficiency and obtain the single-mode propagation characteristics, electron beam lithography, which is an expensive micropattern processing equipment, has to be used.

FIG. 3 is an equivalent refractive index distribution diagram of the microring resonator of FIG. 1, in which the equivalent refractive index should be in the 'C' state in the waveguide, and the ring waveguide is formed in a ring shape having a curved surface. C1 'state.

Therefore, the conventional micro ring resonator has a problem in that the optical wave is shifted to the outer group, causing bending loss in the ring waveguide, and decreasing the Q value.

Meanwhile, in order to use the microring resonator as a building block of the optical SoC, it is very important to effectively control the bandwidth and the center wavelength.

However, in the conventional microring resonator described above, since the coupling strength between the ring of the coupling region constituting the resonator and the bus waveguide is very sensitive in the fabrication process, there is no method of controlling the bandwidth after the device is designed and manufactured. .

In addition, in the case of the conventional resonator, the method of controlling the Q value is simultaneously varied up to the center wavelength of the resonator, and the band extinction ratio is simultaneously changed due to the change of the critical coupling condition to independently control the Q value. There was a problem that can not.

Accordingly, the present invention has been made to solve the problems described above, by changing the radius of the ring resonator, microring resonator filter having a variable bandwidth that can implement a microring resonator having a different Q value and its manufacture The purpose is to provide a method.

Another object of the present invention is to change the center wavelength of light by applying a voltage to the remaining conductors, except for the conductors of a specific resonator, thereby providing a variable bandwidth capable of determining the propagation characteristics of the entire device in a specific resonator with no voltage. The present invention provides a microring resonator filter and a method of manufacturing the same.

It is still another object of the present invention to provide a microring resonator filter having a variable bandwidth in which a Q value can be adjusted by using a mode cut-off voltage so that the transfer characteristics of the entire device appear only in a specific resonator among a plurality of resonators. And a method for producing the same.

A preferred aspect for achieving the above objects of the present invention,

A straight bus waveguide through which light passes;

A plurality of ring waveguides spaced apart from the straight bus waveguide, the plurality of ring waveguides being coupled and resonated with a portion of the light passing through the straight bus waveguide;

A microring resonator filter having a variable bandwidth is provided that includes conductors that apply a voltage to each of the ring waveguides to change the refractive index of each of the ring waveguides.

Another preferred aspect for achieving the above object of the present invention,

Forming a lower clad layer on the substrate;

Forming a core layer on the lower clad layer;

Patterning the core layer on the lower clad layer to form a linear bus waveguide and a plurality of ring waveguides spaced apart from the linear bus waveguide;

Enclosing the straight bus waveguides and the ring waveguides, and forming an upper cladding layer on the lower cladding layer;

A method of manufacturing a microring resonator filter having a variable bandwidth is provided, the method including forming conductors on an upper clad layer corresponding to an upper portion of each of the ring waveguides.

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

4 is a schematic configuration diagram of a microring resonator filter having a variable bandwidth according to the present invention, and includes a straight bus waveguide 100 through which light passes; A plurality of ring waveguides (201, 202, 203, 204) spaced apart from the linear bus waveguide (100) and resonating with a portion of the light passing through the linear bus waveguide (100); And conductors 211, 212, 213, and 214 for applying a voltage to each of the ring waveguides 201, 202, 203, and 204 to change the refractive index of each of the ring waveguides 201, 202, 203, and 204.

Here, each of the conductors 211, 212, 213, and 214 is preferably positioned above the remaining area except for a portion of each of the plurality of ring waveguides 201, 202, 203, and 204 adjacent to the linear bus waveguide 100.

Each of the conductors 211, 212, 213, and 214 is connected to the power sources 301, 302, 303, and 304, as shown in FIG. 4.

In addition, the ring waveguides 201, 202, 203, and 204 are preferably formed in circular ring shapes having different radii.

However, in the present invention, the ring waveguides may be used by mixing a different radius and the same radius.

In addition, as illustrated in FIG. 4, the ring waveguides 201, 202, 203, and 204 are not limited to four, but are formed in two or more.

5 is a schematic cross-sectional view of a microring resonator filter having a variable bandwidth according to the present invention, wherein the linear bus waveguide 100 and the ring waveguide 201 are wrapped with a cladding layer 400, and the linear bus waveguide ( 100 and the ring waveguides 201 have a larger refractive index than the cladding layer 400.

In addition, a conductor 211 is formed on the clad layer 400 spaced apart from the top surface of each of the ring waveguides 201 by a 'd'.

Then, when a voltage is applied to the conductor 211, the refractive index of the region of the ring waveguides 201 existing below the conductor 211 is changed by the applied voltage.

6 is a schematic configuration diagram of a single microring resonator according to the present invention. In the microring resonator filter of FIG. 4, a single microring resonator includes a portion of light passing through the linear bus waveguide 100 to the ring waveguide 201. Combined, the combined light resonates while rotating the ring waveguide 201.

Therefore, the light output from the linear bus waveguide 100 has a periodic band blocking characteristic.

Here, when a voltage is applied to the conductor 211 above the ring waveguide 201, the refractive index of the ring waveguide 201 is changed to change the center wavelength of the resonant light.

In this case, the conductor 211 is preferably an electrode that transfers the applied voltage to the ring waveguide 201 or a heater that is heated to the applied voltage to transfer heat to the ring waveguide 201.

Accordingly, the ring waveguide 201 is formed of an electro-optic polymer whose refractive index is changed by the voltage transmitted from the conductor 211, or a thermo-optic polymer whose refractive index is changed by heat transferred from the conductor 211. Form.

7 is a schematic perspective view of a single microring resonator according to the present invention, in which a straight bus waveguide 100 and a ring waveguide 201 are wrapped with a cladding layer 400, and a cladding layer above the ring waveguide 201. The conductor 211 is formed on the 400.

Here, the conductor 211 is formed on the clad layer corresponding to the upper portion of the ring waveguide 201 except for a portion of the ring waveguide 201 adjacent to the linear bus waveguide 100.

The conductor 211 is formed in an annular shape in which a portion of the conductor 211 is removed so that there is no electrical effect in the region adjacent to the linear bus waveguide 100.

FIG. 8 is a propagation characteristic diagram of a microring resonator filter having a variable bandwidth according to the present invention. As shown in FIG. 4, when four ring waveguides 201, 202, 203 and 204 are coupled to a linear bus waveguide 100, a straight bus Some of the light transmitted to the waveguide 100 is coupled to and resonates with each of the ring waveguides 201, 202, 203, and 204.

At this time, if the ring radiuses of the ring waveguides 201, 202, 203, and 204 are configured differently, as the radius of the ring decreases, the bending loss increases and the Q value decreases.

Therefore, the four ring waveguides 201, 202, 203, and 204 shown in Fig. 4 have smaller Q values in the order of '201', '202', '203', and '204', where the radius of the ring is large.

As a result, the light lambda 1 of each of the ring waveguides 201, 202, 203, and 204 becomes larger in the order of '201', '202', '203', and '204' whose bandwidth is larger than the radius of the ring.

That is, as shown in Figure 8, the ring waveguide '201' 'A', '202' 'B', '203' 'C' and '204' represents the transmission characteristics of 'D'.

Therefore, the present invention can implement a microring resonator having different Q values by changing the radius of the ring resonator.

9A and 9B are propagation characteristics diagrams when voltage is applied to a ring resonator of a microring resonator filter having a variable bandwidth according to the present invention. First, the ring in the four ring waveguides 201, 202, 203, and 204 shown in FIG. When the refractive indices of the ring waveguides '202', '203', and '204' are changed by applying a voltage to the conductors 212,213,214 on the waveguides '202', '203', and '204', the ring waveguide '202' The center wavelength of the band-stopped light by '203' and '204' is shifted from 'λ1' to 'λ2'.

If the voltage is not applied to the conductor 211 above the ring waveguide '201', the center wavelength of the light band-stopped by the ring waveguide '201' does not change.

In this case, as described above, when the ring waveguides 201, 202, 203, and 204 are formed of an electro-optic polymer, the refractive indexes of the ring waveguides 201, 202, 203, and 204 are changed by the voltage transmitted from the conductors, and thus the center of the band-stopped light. The wavelength is shifted.

When the ring waveguides 201, 202, 203, and 204 are formed of thermo-optic polymers, and the conductors function as heaters, the refractive indices of the ring waveguides 201, 202, 203, and 204 are changed by voltages transmitted from the conductors. The center wavelength of the band-blocked light is shifted.

Therefore, as shown in FIG. 9A, the ring waveguides '202', '203', and '204' have a center wavelength of 'λ2', and in the microresonator filter, the overall output characteristics are determined by the ring waveguide '201'. do.

As described above, the microring resonator type filter having the variable bandwidth of the present invention applies the voltage to the remaining conductors, except for the conductors of the specific resonator, and shifts the center wavelength of the light so that the entire element in the specific resonator is not energized. It is possible to determine the propagation characteristics of.

On the other hand, if the voltage applied to the conductor above the ring waveguide is further increased, a mode cut-off phenomenon in which a mode propagated in the ring waveguide is blocked is caused.

Therefore, as shown in FIG. 9B, when the mode cutoff voltage is applied to the conductors 212, 213, and 214 located above the ring waveguides 202, 203, and 204 of FIG. 4, the ring waveguides 202, 203 are applied. In '204', the band-stopped light does not exist, and the band-stopped light exists only in the ring waveguide '201'.

Accordingly, the present invention uses a mode cut-off voltage to block mode propagation of the ring waveguides to which the mode cut-off voltage is applied, so that the transfer characteristic of the entire device is applied to a specific resonator to which the mode cut-off voltage is not applied. Since it can be determined by the, the Q value can be adjusted.

10A to 10F are schematic cross-sectional views illustrating a method of manufacturing a microring resonator filter having a variable bandwidth according to the present invention. First, a lower clad layer 401 is formed on a substrate 500. 10a)

Here, the substrate 500 is preferably a silicon substrate or a glass substrate.

The lower clad layer 401 is formed by spin coating a polymer.

Thereafter, a core layer 402 is formed on the lower clad layer 401. (FIG. 10B)

Subsequently, a photoresist layer 450 is formed on the core layer 402, the photoresist layer 450 is exposed through a mask 480, and the unexposed photoresist layer 450 is etched. Then, the core layer 402 is etched by masking the unetched photoresist layer 450 (FIGS. 10C and 10D).

In other words, the process comprises patterning the core layer 402 on the lower clad layer 401 to form a straight bus waveguide 402a; A plurality of ring waveguides 402b are spaced apart from the linear bus waveguide 402a.

On the other hand, as described above, the waveguide pattern is formed by a lithography process, or is formed by an imprint method.

The core layer is formed of an electro-optic polymer or a thermo-optic polymer.

Next, the linear bus waveguide 402a and the ring waveguides 402b are wrapped to form an upper cladding layer 403 on the lower cladding layer 401. (FIG. 10E)

Finally, conductors 600 are formed on the upper clad layer 403 corresponding to each of the ring waveguides 402b (FIG. 10F).

As described above, the present invention has an effect of implementing a microring resonator having different Q values by changing the radius of the ring resonator.

In addition, the present invention has the effect that, by applying a voltage to the remaining conductors, except for the conductors of the specific resonator, it is possible to control so that the transfer characteristics of the entire device is determined only in the specific resonator is not the voltage.

In addition, the present invention has an effect of controlling the Q value by using a mode cut-off voltage so that the transfer characteristic of the entire device appears only in a specific resonator among the plurality of resonators.

In addition, the present invention can control the Q value by the voltage, there is an effect that can be used as a building block (building block) that is essential for the implementation of optical SoC having a variety of functions.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (10)

A straight bus waveguide through which light passes; A plurality of ring waveguides spaced apart from the straight bus waveguide, the plurality of ring waveguides being coupled and resonated with a portion of the light passing through the straight bus waveguide; A microring resonator filter having a variable bandwidth configured to include conductors that apply a voltage to each of the ring waveguides to change the refractive index of each of the ring waveguides. The method of claim 1, The ring waveguides, A microring resonator filter having a variable bandwidth, characterized by being formed in a circular ring shape having a different radius. The method of claim 1, Each of the conductors, And a microring resonator filter having a variable bandwidth, wherein the filter is positioned above the remaining area except for a portion of each of the plurality of ring waveguides adjacent to the linear bus waveguide. The method according to any one of claims 1 to 3, The conductor, Microring resonator filter having a variable bandwidth, characterized in that the electrode or heater. The method according to any one of claims 1 to 3, The straight bus waveguide and the ring waveguide, Cladding layer, The conductor, Microring resonator filter having a variable bandwidth, characterized in that formed on the cladding layer. The method of claim 5, The straight bus waveguide and the ring waveguide, A microring resonator filter having a variable bandwidth, characterized by consisting of an electro-optic polymer or a thermo-optic polymer. Forming a lower clad layer on the substrate; Forming a core layer on the lower clad layer; Patterning the core layer on the lower clad layer to form a linear bus waveguide and a plurality of ring waveguides spaced apart from the linear bus waveguide; Enclosing the straight bus waveguides and the ring waveguides, and forming an upper cladding layer on the lower cladding layer; And forming conductors on an upper clad layer corresponding to each of the ring waveguides. The method of claim 7, wherein The ring waveguides, A method of manufacturing a microring resonator filter having a variable bandwidth, characterized by being formed in a circular ring shape having a different radius. The method of claim 7, wherein The conductor, A method of manufacturing a microring resonator filter having a variable bandwidth, characterized in that it is an electrode or a heater. The method according to claim 7 or 8, The core layer, A method of manufacturing a microring resonator filter having a variable bandwidth, characterized by consisting of an electro-optic polymer or a thermo-optic polymer.

Images