KR20110030213A - Resonator sensor based on photonic crystal - Google Patents

Abstract

PURPOSE: A resonator sensor based on photonic crystal is provided to detect external conditions such as pressure through change of an optical signal passing through a main waveguide by forming a piezoelectric material into a thin film or a photonic crystal structure. CONSTITUTION: In a resonator sensor based on photonic crystal, a resonator sensor comprises a main waveguide(100), and a resonator(200). The main waveguide is comprised of a core and a cladding surrounding the core and also includes an optical coupling region. The resonator is adjacent to the optical coupling region and receives a branched optical signal while including a piezoelectric material(220) in a certain part.

Description

Resonator sensor based on photonic crystal

The present invention forms a resonator around a main waveguide (optical waveguide), and forms a piezoelectric material whose refractive index changes in accordance with the pressure in the resonator, so that pressure is sensed through a change in an optical signal passing through the main waveguide when pressure is applied. It relates to a resonator sensor using a piezoelectric material.

A sensor is a device or system that can detect any external stimulus. A pressure sensor is a device that measures pressure. Its various uses include various measuring instruments, automatic control, medical, automobile parts, environmental monitoring, and various home appliances. Recently, there has been a growing interest in sensors of smaller and more accurate performance.

Looking at the measuring principle of the current pressure sensor, the displacement, voltage, self-thermal conductivity, and the frequency, etc. are used, and the change in pressure is mainly converted into an electrical signal and measured.

However, the pressure sensor that converts into an electrical signal causes problems such as difficulty in miniaturizing the sensor in accordance with the use of a separate wire and measurement error due to the self heating effect of the wire.

In addition, a bulk piezoelectric material is formed in an optical waveguide and there is a problem in that the manufacturing process is complicated by connecting electric wires.

Therefore, it is required to implement a precise sensor that can be implemented through a simple process and to minimize the measurement error while minimizing the structure.

In order to solve the problems of the prior art, a resonator is formed adjacent to a driving wave path through which an optical signal passes, and a piezoelectric material whose refractive index changes in accordance with an external change in pressure or the like is formed in a thin film or a photonic crystal structure, It is an object of the present invention to provide a resonator sensor using a piezoelectric material capable of detecting external conditions such as pressure by changing a resonant condition of a resonator when a pressure is applied to change an optical signal passing through a main wave path.

In order to achieve the above object, the resonator sensor using the piezoelectric material of the present invention forms a resonator adjacent to a driving wave path through which an optical signal passes. When the piezoelectric material is formed into a thin film or photonic crystal structure in the resonator and a predetermined pressure is applied from the outside, the refractive index of the piezoelectric body changes, the resonance condition of the resonator changes, and an external factor such as pressure through a change of an optical signal passing through the main wave path. The characteristic can be detected.

The present invention is an optical sensor for detecting the characteristics of the optical signal according to the difference in the input and output strength of the optical signal, comprising a core, a leading wave formed by the cladding surrounding the core, is located adjacent to the leading wave, A predetermined portion of the cladding surrounding the core may include a resonator including a piezoelectric material formed of a thin film or photonic crystal structure.

At this time, only wavelengths that meet the resonance conditions (resonance frequency) of the resonator among the optical signals applied to the main waveguide are transmitted into the resonant waveguide forming the resonator while passing through the optical coupling portion formed adjacent to the main waveguide and exist in the resonant waveguide. When pressure is applied to the piezoelectric material, the refractive index changes. In addition, the resonator having the changed refractive index may change the resonance condition to generate a change in the optical signal passing through the main waveguide as the main wave to sense the pressure through the change of the output wavelength.

In the present invention, the resonator may be formed in any one form selected from a ring, disk, and polygon, and the piezoelectric material in the resonator may be formed at a distance from the main wave path.

When the resonator is a ring type, the resonant waveguide formed by the cladding surrounding the core is formed in a ring shape. When the resonator is a polygon, a plurality of linear resonant waveguides may be connected to form a polygon.

In this case, the resonant waveguide forming the polygon may be formed in parallel with the main waveguide, and the optical path changing member may be formed at a portion to which the straight resonance waveguide is connected to reflect the optical signal.

In the present invention, the piezoelectric material may be formed as a thin film or a photonic crystal structure on the upper surface or the side of the optical waveguide forming the resonator, and may be zinc oxide (ZnO), aluminum nitride (AlN), cadmium sulfide (CdS), and pZT (PZT). It may be formed of one material selected from among, and preferably formed of zinc oxide (ZnO).

According to the present invention, the piezoelectric material is provided in the resonator and the external condition (pressure) is determined by the input / output intensity difference of light accompanied by the change of the resonant wavelength. have.

In addition, the pressure is determined by forming a resonator adjacent to the main wave path, and since the process such as direct etching is not performed on the main wave path, the experiment is performed several times by using a single main wave path and a resonator to vary the external conditions. There is an effect that can form a light sensor.

In addition, the present invention is to detect the characteristics of the external conditions by forming a resonator adjacent to the main wave path, it can be applied to various types of optical resonator sensor such as Mach-Zehnder electro-optic modulator (ElEcterooptic Mofulator) It works.

A sensor is a device capable of sensing external stimuli, among which an optical sensor using light shows the highest precision. Thus, a method of manufacturing a resonator sensor using a piezoelectric material as a thin film or a photonic crystal structure so as to sense pressure using an optical sensor having high precision will be described.

Particularly, the optical sensor using the resonator of the present invention moves only the optical signal corresponding to the resonant frequency of the resonator among the optical signals incident on the main waveguide to the resonator, and at this time, the piezoelectric thin film or piezoelectric photonic crystal formed in the resonator is fixed. When pressure is applied, the refractive index changes to change the resonance condition, and the resonance frequency of the optical signal coupled to the resonator changes. Accordingly, the wavelength of the signal coupled to the resonator of the optical signal passing through the main waveguide is changed, and through this, external factor characteristics such as pressure can be detected.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In adding reference numerals to components of the following drawings, it is determined that the same components have the same reference numerals as much as possible even if displayed on different drawings, and it is determined that they may unnecessarily obscure the subject matter of the present invention. Detailed descriptions of well-known functions and configurations will be omitted.

1 is a view showing an optical sensor including a ring resonator according to an embodiment of the present invention.

Referring to FIG. 1, an optical sensor including a resonator includes one main wave path 100 through which light passes, and a resonator 200 formed to be intimate with the main wave path 100. The waveguide 100 and the resonator 200 may be configured to be disposed adjacent to each other on a single substrate.

The main waveguide 100 is a general optical waveguide, and is formed of a cladding layer having a low refractive index and a core layer having a relatively high refractive index, and the core layer is inserted into the cladding layer to transmit an optical signal. Both ends of the main waveguide 100 include an input terminal 102 to which an optical signal is input and an output terminal 104 to which an optical signal is output.

The resonator 200 may have various shapes such as a ring shape, a disk shape, a polygon, and the like, and may be formed in a ring shape in this drawing.

The ring resonator 200 may be formed of a general optical waveguide in the same manner as the main waveguide 100 and may form a ring-shaped resonant waveguide 210. In the present invention, both the main waveguide and the resonant waveguide use an optical waveguide formed of a core layer and a cladding layer, and the optical waveguide used in the resonator is called a resonant waveguide for easy discrimination.

At this time, the portion where the resonant waveguide 210 and the main waveguide 100 are adjacent to the optical coupling portion 110, the optical signal passing through the main waveguide 100 is branched according to the resonance conditions of the resonant waveguide, The optical signal is transmitted to the resonant waveguide 210.

The resonant waveguide 210 includes a piezoelectric material 220 in a predetermined portion, and the piezoelectric material 220 is formed at a distance from the main waveguide 100 and is formed of zinc oxide (ZnO), aluminum nitride (AlN), and cadmium sulfide ( CdS) and one of the materials selected from PZT, and may be formed of any one selected from the group consisting of zinc oxide (ZnO).

The piezoelectric material 220 may be formed as a thin film or photonic crystal structure by etching a predetermined portion of the cladding layer of the resonance waveguide 210.

In addition, the piezoelectric material 220 may change the refractive index of the resonant waveguide 210 by changing the refractive index according to external conditions such as pressure to change the optical signal branched from the optical coupling part 110 and input to the resonator 200. The optical signal output through the main waveguide 100 is changed.

Referring to the operation of the optical sensor including the ring-shaped resonator of Figure 1, the optical signal input through the input terminal 102 of the driving wave 100 proceeds along the driving wave 100 and is located adjacent to the driving wave 100 Branched from the optical coupling portion 110 of the resonator 200, an optical signal having a wavelength corresponding to the resonance condition of the resonator 200 is transmitted to the resonator 200.

The optical signal input to the resonator 200 changes in refractive index in response to external conditions such as pressure, which is a measurement factor, in the piezoelectric material 220 formed in a predetermined portion (all, part, or side) of the resonator 200. Accordingly, the effective refractive index of the resonator 200 also changes.

As the effective refractive index of the resonator 200 changes, the optical coupling condition (resonance condition) from the main waveguide 100 to the resonator 200 is changed. In this case, the effective refractive index of the resonator 200 is changed in response to the pressure applied to the resonator 200, and thus the signal (intensity, phase, etc.) of the light output through the output terminal 104 of the main waveguide 100 is changed. External print characteristics such as pressure can be detected.

That is, in the ring resonator-based optical sensor of FIG. 1, the input light travels along the optical waveguide (main waveguide), and only wavelengths corresponding to the resonance conditions of the ring resonator located next to the optical waveguide are combined. Proceed along the waveguide (main waveguide).

In addition, since the coupling resonance condition is changed according to the phase change of the optical waveguide (resonant waveguide) in the ring resonator, the desired output wavelength can be obtained by changing the phase change. At this time, the resonance condition of the resonator is changed according to the change of the refractive index of the piezoelectric body formed on the upper surface or the side of the ring resonator, and thus the change of the output wavelength can be detected.

In addition, the optical signal whose wavelength is changed is combined with the optical signal passing through the optical waveguide (main waveguide) again in the optical coupling region to measure the characteristics of the optical signal output through the output terminal 104 to detect external factors (pressure). Can be.

2A and 2B are views illustrating an optical sensor including a triangular resonator according to an embodiment of the present invention.

Referring to FIG. 2A, the triangular resonator is used instead of the ring resonator in FIG. 1, and the contents of the main waveguide 100 are the same.

The resonator 200 of FIG. 2A includes three resonant waveguides 210A, 210B, and 210C forming three sides of a triangle, and one resonant waveguide 210A is formed to be parallel to the main waveguide 100.

The piezoelectric material 220 is formed on at least one of the resonant waveguides 210A, 210B, and 210C, and each of the resonant waveguides 210A, 210B, and 210C is formed of an optical path changing member. (230A, 230B, 230C)-for example, total reflection mirrors.

In this case, when the piezoelectric material 220 is formed on the resonance waveguide 210A adjacent to the main waveguide 100, the piezoelectric material 220 is formed on the optical coupling portion 110 of the main waveguide 100 as shown in FIG. 2B. Can be formed. As described above, the piezoelectric material 220 may be formed on the optically coupled portion 110 by using the polygonal and ring resonators, rather than being limited to the triangular resonator of FIG. 2B.

The piezoelectric material 220 is the same as the piezoelectric material formed on the ring-shaped resonant waveguide of FIG. 1, and may have the same structure and shape.

The optical path changing members 230A, 230B, and 230C are disposed at a vertex region, which is a point at which optical waveguides constituting each side of the resonant waveguides 210A, 210B, and 210C are connected to totally reflect the optical signal.

In FIGS. 2A and 2B, three resonator waveguides and optical path changing members are used by restricting the resonator to a triangle. However, the present invention is not limited thereto, and a polygonal resonator, such as a quadrangle, may be configured. The piezoelectric material may be formed on at least one of the resonant waveguides to induce a change in refractive index of light and a change in resonant wavelength according to an external condition (pressure).

The operation of the optical sensor including the triangular resonator of FIG. 2A is similar to that of the optical sensor including the ring resonator of FIG. 1.

In more detail, the optical signal input through the input terminal 102 of the main waveguide 100 proceeds along the main waveguide 100 and the main waveguide 100 of the triangular resonator 200 in the optical coupling region 110. Coupled with a parallel resonant waveguide 210A.

The optical signal coupled to the resonant waveguide 210A is reflected by the optical path changing members 230A, 230B, and 230C formed at each vertex of the resonant waveguides 210A, 210B, and 210C, and then is inside the resonant waveguides 210A, 210B, and 210C. In the clockwise direction, the phase is changed according to the effective refractive index of the resonant waveguide changed by the piezoelectric material 220 in which the optical signal is reacted with an external factor to change the coupling resonance condition.

Subsequently, the optical signals traveling in the resonant waveguides 210A, 210B, and 210C are coupled to the main waveguide 100 in the optical coupling region 110 and output through the output terminal 104.

As described above, since the resonance conditions of the resonant waveguides 210A, 210B, and 210C are changed in response to external factors such as the pressure reacting to the piezoelectric material 220 of the resonant waveguides 210A, 210B, and 210C, the main waveguide 100 may be changed. The intensity of the optical signal output through the output terminal 104 may be measured to detect a characteristic of an external factor.

3A and 3B illustrate an optical sensor including a disc resonator according to an embodiment of the present invention. FIG. 3A is a top view and FIG. 3B is a side view.

Referring to FIGS. 3A and 3B, the disk-type resonator is used instead of the ring-shaped resonator in FIG. 1, and the contents of the main waveguide 100 are the same, and the disk-shaped resonator 200 is also the ring-shaped resonator. Similarly, the piezoelectric material 210 is included in a predetermined portion of the clad region.

 In the disc-shaped resonator 200 of FIGS. 3A and 3B, an optical signal input through the input terminal 102 of the main waveguide 100 proceeds along the main waveguide 100 and then the resonance condition of the disc-shaped resonator 200. The combined wavelengths are combined into the resonator 200, and the uncombined wavelengths travel toward the output terminal 104.

In addition, as the coupling resonance condition is changed according to the phase change in the disc type resonator 200, the desired output wavelength may be obtained by changing the phase change.

The dielectric material 210 formed in the clad region of the disc resonator 200 responds to a pressure or the like, which is a measurement factor, thereby changing the effective refractive index of the resonator 200. The optical coupling condition from the main waveguide 100 to the resonator 200 is changed according to the changed effective refractive index.

In this case, the effective refractive index of the resonator 200 is changed in response to the pressure applied to the clad region of the resonator 200, and thus the amount of light output through the output terminal 104 of the main waveguide 100 is changed. External factor characteristics such as pressure can be detected.

1, 2A, 2B, 3A, and 3B are all a structure in which a resonator including piezoelectric material is formed adjacent to a driving wave path, and the driving wave used is the same, and the resonant waveguides are the same, and the external signal is changed according to the change of the optical signal. The method of detecting the characteristics of the factor (pressure) is similar. However, there are differences in the position where the piezoelectric material is formed in the resonator and additionally required components (light path changing member), etc., depending on the shape of the resonator.

In the drawings, the piezoelectric material is briefly described in the resonator, that is, on the resonant waveguide. In the resonant waveguide formed of the core and the cladding, a predetermined portion of the cladding or the cladding formed only on the top of the core is formed. The piezoelectric material may be formed in a thin film form on the exposed cladding layer by etching, or the piezoelectric material may be formed on the exposed cladding layer using a nano pattern or a selective growth method to form a photonic crystal structure.

4A and 4B illustrate a Mach-gender electro-optic modulator sensor according to an embodiment of the present invention.

A Mach-Zehnder elecrerooptic modulator optical element travels along an optical waveguide and then splits off by branching into the optical waveguide, changing the external factor (pressure) on one side of the phase to change the phase When a change occurs and the phase shift modulated by the optical path difference is extracted, a signal of an external factor can be demodulated. In more detail, a phase change occurs on the upper surface of one branched optical waveguide according to the change of the refractive index of the piezoelectric body, and the phase change modulated by the optical path difference can be extracted.

The optical waveguides of the general photonic crystal structure are arranged at shorter intervals than the wavelength. When the Mach-Gender electro-optic modulator optical sensor is implemented through this photonic crystal structure, the change in effective refractive index of the optical waveguide can be measured with a minimum unit area. have.

In addition, when a photonic crystal is formed in an optical waveguide, only a specific wavelength passes, and if another optical waveguide is placed next to the optical waveguide, only a specific wavelength does not pass. When the refractive index of the photonic crystal is changed, the optical characteristic of the specific wavelength changes the resonance characteristic, causing the resonance wavelength to shift or the phase change due to the optical path difference.

In other words, when the piezoelectric refractive index of the photonic crystal structure is changed, the resonance condition is changed, and thus the output is changed or a phase change occurs, so that the change in the output wavelength can be measured.

Referring to FIG. 4A, an optical sensor is formed by additionally configuring a triangular resonator of FIG. 2A using one optical waveguide of the two optical waveguides constituting the Mach-Gender field optical modulator as the main waveguide. In this case, the resonator may be formed in a ring shape, a polygon shape, or a disk shape.

Looking at the optical signal flow of the optical sensor formed as described above, the optical signal incident on the input terminal 302 through the two different optical waveguides (310, 320) are combined again into one light and then output to the output terminal (304).

At this time, the optical signal incident through the one optical waveguide 310 is coupled to the optical waveguide constituting the resonant waveguides 330A, 330B, and 330C disposed in parallel with the optical waveguide 310 and input to the resonant waveguide 330A. .

The optical signal input to the resonant waveguide 330 is reflected by the optical path changing members 340A, 340B, and 340C disposed at vertices of the resonant waveguide 330A to circulate the resonant waveguides 330A, 330B, and 330C.

Reacts with external factors such as pressure in piezoelectric materials 350A and 360B formed on the upper or side surfaces (see FIG. 4B) of the resonant waveguides 330B and 330C between the respective optical path members 340A, 340B and 340C. The effective refractive indices of the resonant waveguides 330A, 330B, and 330C are changed according to external factors such as the pressure reacting in the materials 350A and 360B.

Due to the change in the effective refractive index of the resonant waveguides 330A, 330B, and 330C, the optical signal that is circulated in the resonant waveguides 330A, 330B, and 330C is generated from the resonant waveguides 330A, 330B, and 330C. The phase is changed by recombination with the optical signal of the optical waveguide 310 parallel to the resonant waveguide 330A among the optical waveguides 310 and 320.

Therefore, since the constructive or destructive interference between optical signals due to the phase difference of the optical signals passing through two different optical waveguides 310 and 320 of the Mach-Gender electro-optic modulator occurs, the exit port of the Mach-Gender electro-optic modulator By measuring the optical signal output through the can detect the characteristics of the external factors such as pressure.

As described above, it has been described with reference to a preferred embodiment of the present invention, but those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

1 is a view showing an optical sensor including a ring resonator according to an embodiment of the present invention.

2A and 2B illustrate an optical sensor including a triangular resonator according to an embodiment of the present invention.

3A and 3B illustrate an optical sensor including a disc resonator according to an embodiment of the present invention.

4A and 4B illustrate a Mach-gender electro-optic modulator sensor according to an embodiment of the present invention.

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

100: lead wave 102, 302: input terminal

104, 304: output 110: optical coupling region

200: resonator

Resonant waveguide: 210, 210A, 210B, 210C, 330A, 330B, 330C

220, 350A, 360B: Piezoelectric Materials

230A, 230B, 230C, 340A, 340B, 340C: light path changing member

300: Mach-gender electro-optic modulator sensor

310, 320: optical waveguide

Claims (7)

In the resonator sensor for detecting the characteristics of the optical signal input and output using the resonator, A main waveguide formed of a core and a cladding surrounding the core and including an optical coupling region to which an optical signal is branched; And A resonator formed adjacent to the photocoupling region, for receiving a branched optical signal and including a piezoelectric material in a predetermined portion; Resonator sensor comprising a. The resonator sensor as claimed in claim 1, wherein the resonator is formed in one of ring, disk, and polygonal shapes. The method of claim 2, wherein when the resonator is a polygon, The resonator is connected to a plurality of resonant waveguides formed by a cladding surrounding the core to form a polygon, one side of the polygon is formed in parallel with the main waveguide, the predetermined portion of at least one surface of the resonant waveguide of the polygon A resonator sensor comprising a piezoelectric material. The method of claim 3, wherein when the resonant waveguide forms a polygon, And a light path changing member formed at a connection portion of the resonant waveguide and reflecting an optical signal. The method of claim 2, wherein when the resonator is a ring or polygon, And a piezoelectric material is formed in the optical coupling region of the main waveguide and the optical coupling region of the resonator. The method of claim 1, wherein the piezoelectric material is A resonator sensor, which is formed of one selected from zinc oxide (ZnO), aluminum nitride (AlN), cadmium sulfide (CdS), and piji (PZT). The method of claim 1, wherein the piezoelectric material is The resonator sensor is formed on the upper surface or the side of the optical waveguide, and formed in a thin film or photonic crystal structure.

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