KR20110030205A - Photonic crystal based optical sensor and its manufacture method - Google Patents

Abstract

PURPOSE: A photonic crystal based optical sensor and a manufacture method thereof are provided to simplify a configuration by using a sensor which is sensitive in comparison to a sensor extracting electric polarization. CONSTITUTION: In a photonic crystal based optical sensor and a manufacture method thereof, an optical sensor has a piezoelectric material in an etched part of a clad layer surrounding a core. The piezoelectric material is made of one of ZnO(zinc oxide), AlN(aluminum-nitride), CdS(cadmium sulfide), PZT. The piezoelectric material is formed into a thin film structure or a photonic crystal structure.

Description

Photonic crystal based optical sensor and its manufacture method

The present invention provides an optical sensor using a thin film of a piezoelectric material and a photonic crystal structure for forming a piezoelectric thin film or a piezoelectric photonic crystal on a portion of an optical waveguide and detecting a change in pressure by detecting a change in an optical signal with respect to a pressure applied thereto. It is about.

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 converting into an electrical signal causes problems such as difficulty in miniaturizing the sensor structurally and measurement error due to the self heating effect of the wire according to the use of a separate wire.

Therefore, while achieving a structural miniaturization, it is required to implement a precise sensor that minimizes measurement errors.

In order to solve the problems of the prior art, the present invention includes a piezoelectric element that reacts to pressure in an optical waveguide so that light propagates onto the optical waveguide is changed from a changed refractive index of the piezoelectric material so that its characteristics change, and the change is used. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical sensor using a thin film of a piezoelectric material and a photonic crystal structure for detecting pressure applied thereto, and a method of manufacturing the same.

In order to achieve the above object, an optical sensor using the thin film and the photonic crystal structure of the piezoelectric material of the present invention and a method of manufacturing the same, the piezoelectric thin film or the piezoelectric photonic crystal are formed by etching a cladding layer of an optical waveguide, and the light is changed according to the change of the piezoelectric refractive index. It is possible to implement a precise sensor that detects external factors such as pressure from the change in the characteristics of light passing through the waveguide.

The present invention relates to an optical sensor that detects an amount of pressure by using a characteristic of light whose refractive index is changed by a piezoelectric material. The present invention relates to a predetermined portion of a clad layer formed of a material having a lower refractive index than the core and surrounding the core. May be etched and a piezoelectric thin film or a piezoelectric photonic crystal may be formed on the etched portion.

In this case, the etched cladding layer may prevent the core from being exposed as the upper portion of the core or the upper portion of the portion where the core does not exist. In addition, the piezoelectric photonic crystals formed on the cladding layer etched at predetermined portions are formed at regular intervals to pass only a specific wavelength. When the refractive index of the piezoelectric material changes according to pressure, the wavelength of the output light changes to form a sensor sensitive to pressure characteristics. can do.

In the present invention, the piezoelectric thin film may be formed of one material selected from zinc oxide (ZnO), aluminum nitride (AlN), cadmium sulfide (CdS), and piji (PZT), preferably zinc oxide (ZnO). ) Can be formed.

In addition, the present invention relates to a method for manufacturing an optical sensor using an optical waveguide, the method comprises the steps of etching a predetermined portion of the upper clad layer so that the core surrounded by the upper and lower cladding layer of the optical waveguide is not exposed. It includes, and may include forming a piezoelectric material on the etched portion.

In this case, the optical waveguide is formed by forming a core on the upper cladding layer, and surrounding the core to form an upper cladding layer on the lower cladding layer, and the etching cladding layer is preferably an upper cladding layer. Alternatively, the lower clad layer may be formed by etching.

In the forming of the piezoelectric material, the piezoelectric material may be formed into a thin film or a photonic crystal structure. When the piezoelectric material is formed into a photonic crystal structure, a piezoelectric thin film may be formed on an exposed cladding layer which is etched and then using a nano pattern. By etching, the piezoelectric photonic crystal may be formed to have a predetermined interval in the etched portion of the upper clad layer.

In addition, in the case of forming the photonic crystal structure, after forming a buffer layer on the etched and exposed cladding layer, a nanopattern may be formed, a liquid piezoelectric material is poured, and the piezoelectric material may be selectively grown to form a photonic crystal. In this case, the buffer layer may be omitted as it is used to facilitate growth when the growth process using different materials.

The present invention provides a Mach-Gender field optical modulator optical sensor comprising one input terminal and one output terminal and including at least two optical paths, wherein an incident optical signal is split at least once. It is possible to form an optical sensor using a thin film of material and a photonic crystal structure.

According to the present invention, the piezoelectric material is formed into a thin film or photonic crystal structure to implement an optical sensor, thereby realizing the electric polarization generated by mechanical deformation, using a very sensitive light as compared to a sensor type for extracting the shape of electricity to the outside. Since additional materials such as wires are not required to extract the signal, the structure is miniaturized, and it is possible to realize a sensitive and precise sensor.

In addition, since the piezoelectric thin film and the piezoelectric photonic crystal structure are formed not only on the upper part of the core of the optical waveguide, but also on the etching portion of the clad layer in which the core does not exist, the core is less likely to be damaged by a strong pressure, thereby enabling a reliable optical sensor. There is.

In addition, the present invention is to form a piezoelectric thin film or piezoelectric photonic crystal by etching the cladding layer of the optical waveguide, which can be applied to optical sensors of various fields such as planar optical waveguide, Mach-Zehnder ElEcterooptic Mofulator It works.

A sensor is a device capable of sensing external stimuli, and among them, an optical sensor using light shows the highest precision. Thus, a method of manufacturing an optical sensor capable of detecting pressure by using an optical sensor having high precision will be described.

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.

1A to 1E are cross-sectional views illustrating a method of manufacturing an optical sensor including a piezoelectric body according to an embodiment of the present invention.

The optical sensor is a piezoelectric material formed by etching a predetermined portion of the optical waveguide 100, the optical waveguide 100 forms a core 120 having a higher refractive index than the cladding layer on the lower clad layer 110, the core The upper cladding layer 130 is formed on the lower cladding layer 110 and surrounds the 120 (see FIGS. 1A to 1C).

At this time, the lower clad layer 110 and the upper clad layer 130 is formed of the same material, and separated for convenience of description, but preferably may be formed by inserting a core inside the one clad layer.

Referring to FIG. 1D, when a pressure is applied, a predetermined portion of the optical waveguide 100 is etched to form a material (piezoelectric) that affects light passing through the optical waveguide 100, that is, to change the refractive index of the light. do.

Although not limited to the present invention, the portion to be etched is the upper cladding layer 130, the upper portion of the core 120 or the upper portion of the upper cladding layer 130 in which the core 120 is not present, that is, the refractive index is higher than that of the core. It may include a portion consisting of only a small cladding layer, and may be etched so that the core 120 is not exposed when the upper portion of the core 120 is etched.

For details, refer to FIGS. 2A and 2B below.

Referring to FIG. 1E, the piezoelectric thin film 210, which is a piezoelectric material, is formed on the upper clad layer 130 of the portion etched in FIG. 1D.

The piezoelectric thin film 210 may be formed by various methods such as physical vapor deposition, chemical vapor deposition, and liquid phase. In order to exhibit excellent piezoelectric properties, a single crystal thin film having a uniform thickness is required. At this time, the thickness of the piezoelectric thin film may be used by varying the thickness according to the piezoelectric properties to be measured as several hundred nm ~ several um.

More specifically, the piezoelectric material may be formed using a physical vapor deposition method such as sputter, molecular beam evaporator (MBE), organometallic vapor deposition (MOCVD) or chemical vapor deposition, or the like to form a good crystallinity by liquid phase method. It grows into a thin film form.

The piezoelectric material is a material in which polarization is induced inside the material when the external mechanical pressure is applied or mechanical deformation is caused by an external electric field. However, the piezoelectric material is not limited thereto. In the present invention, zinc oxide (ZnO) and aluminum nitride (AlN) are used. , Cadmium sulfide (CdS), and may be formed of one material selected from PZT, preferably zinc oxide (ZnO).

In general, a sensor using a piezoelectric material mainly applies electric polarization generated by mechanical deformation, and includes vibration, acceleration, angular velocity, and acoustic sensor. Another characteristic of the piezoelectric material is that the refractive index is reduced by pressure and external stress. Indicates a change.

In the present invention, a piezoelectric material (a piezoelectric thin film or a piezoelectric photonic crystal) is formed on an optical waveguide in order to take advantage of the characteristic of changing the refractive index by pressure, and when the pressure is applied to the piezoelectric material, the refractive index of the piezoelectric material changes, and at this time, The influence of the light passing through the waveguide can be affected to detect the pressure applied from the outside through the changed light.

2A and 2B are cross-sectional views illustrating optical sensors having different positions of forming a piezoelectric body according to another exemplary embodiment of the present invention.

2A and 2B illustrate an etching portion of the upper cladding layer 130 for forming a piezoelectric body in the optical waveguide 100 formed by FIGS. 1A to 1C, wherein the piezoelectric thin film 210 is formed of a core 120. It is shown that the core 120 is formed in a portion where the core 120 is not present.

When performing the etching process (using dry etching or wet etching) in the portion where the core 120 does not exist when etching the upper clad layer 130 as shown in Figure 2a, the risk of damage to the core 120 occurs depending on the degree of etching, In the case of FIG. 2B, there is no risk of damaging the core 120 by etching the portion where the core 120 does not exist, that is, the portion composed only of the cladding layers 110 and 130.

In addition, in the optical waveguide, when the light passes through the core, the light proceeds through all of the cladding layers around the core, so that light can be detected even at a predetermined distance from the core, so that only the cladding layers 110 and 130 are formed. Even if the piezoelectric thin film 210 is formed in the portion, the difference in effect is not large in the sensitivity portion of the light. Therefore, in the case of the optical sensor in which the piezoelectric thin film 210 is formed on the side surface of the core 120 as shown in FIG. 2B, the sensitivity of the optical sensor does not affect the sensitivity.

3A to 3B are cross-sectional views illustrating an optical sensor including a photonic crystal according to an exemplary embodiment of the present invention.

3A illustrates the piezoelectric photonic crystal 220 instead of the piezoelectric thin film 210 in the process of FIG. 1D, and FIG. 3B forms the piezoelectric photonic crystal 230 instead of the piezoelectric thin film 210 in the process of FIG. 2B.

The piezoelectric photonic crystal 230 may be formed through an etching process or a growth process, and the etching process is formed by using a nano patterning process, and forms a thin film piezoelectric material on the etched and exposed cladding layer 130, Photonic crystals may be formed by etching a piezoelectric material in the form of a thin film using a nano pattern using electron beam lithography, nano-imprint, and laser interference lithography.

The growth process is performed by forming a buffer layer (not shown) on the etched and exposed cladding layer 130, and then forming a nano pattern, and selectively growing the liquid crystal source of the piezoelectric material using the pattern to form a piezoelectric photonic crystal ( 230 may be formed.

According to the present invention, in order to form an optical sensor, a piezoelectric material is formed in a thin film or a photonic crystal structure on an optical waveguide, which can be miniaturized compared to a bulk (lump) piezoelectric sensor and can form an optical sensor having improved sensitivity.

For reference, when the piezoelectric material is formed into a photonic crystal structure, the sensitivity is improved because the effective piezoelectric constant is relatively larger than that of the bulk type (M. H. Zhao. Et. Al. NANO LETTERS, 4 (4) 587 2004).

4 is a diagram illustrating a Mach-gender electro-optic modulator sensor according to an embodiment of the present invention.

Referring to FIG. 4, a Mah-gender field optical modulator including one input terminal 410 and one output terminal 420 and having two optical paths (optical waveguides 430A and 430B) branched in the middle path is illustrated. . In this case, although the drawing is divided into two light paths 430A and 430B with one branch, the number of light paths may be changed according to the branch without being limited thereto.

In FIG. 4, the piezoelectric material 440 is formed on one optical waveguide 430B of the two optical waveguides 430A and 430B, as shown in FIGS. 1E, 2B, 3A, and 3B. Light incident from 410 is branched and passes through the respective optical waveguides 430A and 430B. In addition, the light passing through the portion of the optical waveguide 430B including the piezoelectric material 440 changes in wavelength of light due to the change in refractive index of the piezoelectric material. The light is output by being combined with the light passing through 430A.

In addition, even in the case of the optical waveguide 430A in which the piezoelectric material 440 is not formed, the refractive index of light passing by the piezoelectric material 440 of the adjacent optical waveguide 430A may be affected.

The piezoelectric material 440 is a piezoelectric thin film or a piezoelectric photonic crystal, and details thereof will be described with reference to FIGS. 1A through 1E, 2A, and 2B, 3A, and 3B.

At this time, since the piezoelectric material 440 formed on the upper or side surfaces of any one of the optical waveguides 430A and 430B reacts with external recognition such as pressure, the light passing through the different optical waveguides exhibits a phase difference. Therefore, the difference between the characteristics of the light measured at the output terminal 420 and the characteristics of the light incident at the input terminal 410 may be detected, and thus the pressure applied to the optical waveguide may be sensed.

More specifically, optical waveguides having a general photonic crystal structure are arranged at shorter intervals than wavelengths. When the Mach-Gender electro-optic modulator optical sensor is implemented through the photonic crystal structure, the effective refractive index of the optical waveguide is changed in a minimum unit area. It can be measured.

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.

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.

1A to 1E are cross-sectional views illustrating an optical sensor including a piezoelectric body according to an embodiment of the present invention.

2A and 2B are cross-sectional views illustrating optical sensors having different formation positions of piezoelectric bodies according to another exemplary embodiment of the present invention.

3A to 3B are cross-sectional views illustrating optical sensors including a photonic crystal according to an embodiment of the present invention.

4 is a diagram illustrating 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, 430A, 430B: optical waveguide 110: lower clad layer

120: core 130: upper clad layer

210: piezoelectric thin film 220: piezoelectric photonic crystal

410: input terminal 420: output terminal

440: piezoelectric material

Claims (9)

An optical sensor for etching a predetermined portion of the clad layer formed surrounding the core, the pressure sensor by forming a piezoelectric material on the etched portion. The method of claim 1, wherein the piezoelectric material is An optical 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 An optical sensor comprising a thin film structure or a photonic crystal structure. In the method for manufacturing an optical sensor using an optical waveguide, the method Etching a predetermined portion of the upper clad layer so that the core surrounded by the upper and lower clad layers of the optical waveguide is not exposed; And Forming a piezoelectric material on the etched portion; Optical sensor manufacturing method comprising a. The method of claim 4, wherein the predetermined portion of the upper cladding layer, And a portion consisting of only the top or cladding layer of the core. The method of claim 4, wherein forming the piezoelectric material comprises: And forming a piezoelectric material in a thin film or in a photonic crystal structure on the etched portion. The method of claim 6, wherein the photonic crystal structure, And forming a piezoelectric material on the etched portion in a thin film, and then etching the nano-pattern or forming a selective growth on the etched portion. 8. The method of claim 7, wherein said selective growth is And forming a piezoelectric material through a nano pattern after forming a buffer layer on the etched portion to selectively grow. A Mah-gender field optical modulator optical sensor comprising an input terminal and an output terminal and including at least two optical paths, wherein at least one branched light signal is branched at least once, The light sensor manufactured by the manufacturing method of claim 4 to 8 in the one optical path, Mach-gender field optical modulator optical sensor.

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