KR100623522B1 - Method for making light modulator - Google Patents

Abstract

The present invention relates to a method for manufacturing a surface plasmon resonance optical modulator based on a diffraction grating structure, in particular to easily implement a single, multiple and multiple diffraction gratings at the interface between a metal film and an electro-optic material film using a pattern mask. A first deposition step for the purpose of depositing a metal film on the upper surface of the substrate; A second deposition step of installing a pattern mask in front of the metal film and depositing a metal to form a diffraction grating; And sequentially forming an electro-optic material film and a transparent electrode on the diffraction grating.

Optical modulator, surface plasmon resonance, metal film, dielectric, electro-optic polymer, diffraction grating, mask

Description

Method for manufacturing light modulator {Method for making light modulator}             

1 is a cross-sectional view showing a conventionally known prism coupled optical modulator.

Fig. 2 is a sectional view showing the optical modulator of the first embodiment of the present invention.

3 is a view for explaining a production method of the first embodiment of the present invention.

4 is a cross-sectional view showing an optical modulation chip according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating the manufacturing method of the second embodiment of the present invention. FIG.

Fig. 6 is a sectional view showing the optical modulator chip according to the third embodiment of the present invention.

The figure explaining the manufacturing method of 3rd embodiment of this invention.

Fig. 8 is a sectional view showing the optical modulator chip according to the fourth embodiment of the present invention.

9 is a view for explaining a production method according to the fourth embodiment of the present invention.

The present invention relates to a method for manufacturing a grating-coupled surface plasmon resonance (GC-SPR) optical modulator based on a diffraction grating structure, and more particularly, to a metal film and an electro-optic material film using a pattern mask. The present invention relates to a manufacturing method for facilitating the implementation of single, multiple and multiple diffraction gratings at an interface.

Light modulation uses the principle that light incident on the interface between a metal and a dielectric is absorbed when it meets surface plasmon resonance (SPR) conditions, and is reflected when it does not meet the resonance condition. It is very sensitive to the refractive index of the light source, the wavelength and the incident angle of the light source, the structure of the diffraction grating, etc. In particular, the present invention is to implement a diffraction grating of multiple and multiple structures having a fine period to detect the desired wavelength from the incident light.

Surface plasmon is a property observed at the interface between a metal and a dielectric, and refers to charge-density oscillation generated as a result of the energy of incident light excited free electrons in the metal. This is a transverse magnetic polarized light (TM) that travels along the interface, exhibiting maximum values at the interface of the two media and decreasing exponentially in the direction perpendicular to the metal surface. Surface plasmon resonance occurs under the condition that the TM-direction wave vector of the incident light coincides with the wave vector (K _sp ) of the surface plasmon. At this time, the incident light is absorbed by the surface plasmon, so the reflectance of the incident light is drastically reduced. Therefore, it is possible to adjust the reflected light intensity (light intensity) by adjusting the refractive index of the material, the incident angle and the wavelength of the light source that affects the surface plasmon resonance.

However, surface plasmon resonance does not occur at all interfaces of the metal-dielectric. For example, light incident on the planar metal-dielectric interface of metal and dielectric in air does not generate surface plasmon resonance because the wave vector of the incident light is always smaller than the wave vector (K _sp ) of the surface plasmon wave. Therefore, in order to implement (observe) surface plasmon resonance, a method of increasing the wave vector value of the incident light and the wave vector (K _sp ) of the incident light using a prism is required.

Figure 1 shows a known method of using a high refractive prism to optically excite surface plasmon waves. This is called Kretschmann type or prism-coupled surface plasmon resonance.

When incident light is irradiated to the metal film 1 deposited on the prism at an angle exceeding the critical angle, the wave vector value of the incident light is increased by the high refractive prism 3. At this time, by adjusting the angle of incidence of the light incident on the prism 3, if the wave vector value of the incident light is adjusted to match K _sp , surface plasmon resonance is observed.

Since the surface plasmon resonance phenomenon is very sensitive to the refractive index change of the dielectric 5, it is applied to chemical reactions and fine material analysis on the metal surface. The main application of surface plasmon resonance is in the field of bio-sensing, and most of them use the Kretschmann method. That is, when the antibody is coated on the metal film in contact with the prism, and then exposed to the antigen (protein) to be analyzed, the refractive index of the dielectric in contact with the metal is changed as a result of the binding of the antibody-antigen molecule, thereby performing micromolecule detection and concentration analysis. You can do it.
Representative methods for realizing surface plasmon resonance by adjusting the refractive index of the dielectric are as follows.
First, it is a method of controlling the refractive index of the dielectric by changing the concentration by adjusting the amount of the sample attached to the surface of the metal film, such as the antibody-antigen binding described above, which is mainly applied in the field of biosensors such as sample analysis.
Second, a method of utilizing the electro-optic effect of a dielectric whose refractive index changes with applied voltage, one of the most representative systems is liquid crystal, which uses a method in which the entire molecule is rotated by voltage, and the other is a nonlinear optical molecule or As an electro-optic molecule, this is a method that uses the Pockels effect, in which an electron transition occurs in a molecule due to a voltage and the refractive index changes.

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Korean Patent Laid-Open Publication No. 2000-0077236 (December 26, 2000) discloses a structure using an optical modulator using surface plasmon resonance.
The optical modulator according to the above publication proposes a liquid crystal material as an electro-optic material (dielectric), and shows an improved structure of causing surface plasmon resonance using a pair of prisms and diffraction gratings.

The optical modulator configured as described above is used as a display device and a light source for realizing color display without using a color filter or a color light source.

Among the above-mentioned prior arts, the Kretschmann type optical modulator has a problem of using an expensive high refractive prism in order to realize desired optical modulation, and also due to the large prism, it is difficult to reduce the size, high integration, and mass production of the device. There is a problem.
In addition, although the Korean Patent Laid-Open Publication No. 2000-0077236 uses a liquid crystal as an electro-optic material, that is, a dielectric, in the second method of the related art described above, a light modulator is used. There is a disadvantage in that the response speed is slow, and as a result, there are many difficulties in practical use as an optical modulator.
On the other hand, in the second method described above, the latter electro-optic molecule is a material having a response speed of about 10 to ¹² times faster than that of liquid crystal, and as a result, it is known to be suitable for implementing an optical industry optical modulator including optical communication, optical interconnect, and the like. have.

In consideration of the foregoing, the present invention implements a diffraction grating structure in place of a high refractive prism and adjusts the refractive index of a dielectric material, and the refractive index of the material under voltage is changed by the Pockels effect. The object of the present invention is to enable the manufacture of optical modulators for the mining industry.
In addition, the present invention implements a diffraction grating having a period finer than the wavelength of incident light at the interface between the metal film and the dielectric, so that it is easier to manufacture a single, multiple and multiple diffraction grating having a fine period using a pattern mask. The purpose is to.

In order to achieve the above object, the present invention comprises a first deposition step of depositing a metal film on the upper surface of the substrate; A second deposition step of installing a pattern mask in front of the metal film and depositing a metal to form a diffraction grating; And it proposes a method of manufacturing an optical modulator comprising a step of sequentially forming an electro-optic material film and a transparent electrode on the diffraction grating.

Since the optical modulation device of the present invention is connected to a power source to the metal film and the transparent electrode, and provided with a light source and a light receiving unit for irradiating the p-polarized light toward the transparent electrode.

와 같은 전기광학무기재료를 사용할 수 있다. 이러한 전기광학물질막으로 사용될 수 있는 비선형광학특성을 가진 전기광학고분자 및 전기광학무기재료는 넓은 의미의 유전체로 정의할 수 있다.Preferably, in the manufacturing method of the present invention, the metal is a single metal or alloy such as gold, silver, copper, aluminum, or the like.
In addition, in the present invention, the electro-optic material film is a material having a nonlinear optical characteristic whose refractive index changes according to the voltage applied by the Pockels effect. Herein, a material having a nonlinear optical characteristic means a material having an electrooptic characteristic and exhibiting a Pockels effect. The greater the nonpolar characteristic, the better the electrooptic characteristic.

Electro-optical inorganic materials such as may be used. Electro-optic polymers and electro-optic inorganic materials having nonlinear optical characteristics that can be used as the electro-optic film can be defined as dielectrics in a broad sense.

As another embodiment of the present invention, the diffraction grating may be formed in multiple units having different lattice periods.

In still another embodiment of the present invention, there is provided a semiconductor device comprising: a first deposition step of forming a plurality of unit metal films by installing a base mask and depositing metal in front of a substrate; A second deposition step of forming a plurality of diffraction gratings by installing a pattern mask in front of the plurality of unit metal films and depositing metal again; And it proposes a method of manufacturing an optical modulator comprising the step of sequentially forming an electro-optic material film and a transparent electrode on the substrate and the diffraction grating.

Here, each of the diffraction gratings may be formed in a multiple structure having a different lattice period.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described based on an accompanying drawing.

2 shows the basic structure constituting the optical modulation device of the present invention.

As can be seen from the drawings, in the schematic system constituting the optical modulation device of the present invention, the optical modulation chip 10, the light source unit 30 for providing light to the optical modulation chip 10, and It consists of a light receiving unit 50 for detecting the light reflected from the optical modulation chip 10.

와 같은 전기광학무기재료 물질을 사용한다. 여기서, 전기광학고분자(nonlinear optical polymer)는 비선형특성(hyperpolarizability)이 클수록 전기광학 효과가 우수한 물질로서, "이명현 박사의 비선형광소자"라는 참조문헌을 통하여 알 수 있으며, 아래의 화학식 1과 같은 구조적 특성을 갖는 물질로 표시될 수 있다.

여기서, D는 전자주게(doners)이고, A는 전자받게(acceptors)이며, Conjugation bridge는 긴 공핵구조(π-electron bridge)를 나타내고 있다.
이러한 전기광학고분자 물질은 상기 구조적 특성의 유니트를 분자구조 내에 포함하는 고분자로서, 전자주게에서 공핵구조를 통해 전자받게로 전자 전이가 효율적으로 이루어지므로, 이로 인해 전기광학고분자의 비선형특성값이 증가하게 되고, 그 결과 투명전극(17)과 금속막(13)에 전압이 인가되면 재료의 굴절율이 변화하는 것이다.The surface plasmon resonance optical modulation chip 10 has a structure in which the substrate 11 constituting the base, the metal film 13, the electro-optic material film 15, and the transparent electrode 17 are sequentially stacked. The metal film 13 and the transparent electrode 17 are connected to the power source 19.
In particular, the present invention utilizes the Pockels effect of an electro-optic material in which electron transfer in a molecule is efficiently performed by voltage as a method of controlling the refractive index of a dielectric in order to use the surface plasmon resonance phenomenon.
As a technical realization means for this, by connecting the power source 19 to a plurality of units of the metal film 13 and the transparent electrode 17 and applying a voltage, the electro-optic material film 15 positioned therebetween has a Pockels effect. This is to control the light modulation by changing the refractive index.
To this end, in the present invention, an electro-optic polymer film having a wider dielectric material and a narrower non-linear optical characteristic may be used as the electro-optic material film 15.

Uses electro-optical inorganic materials such as Here, the nonlinear optical polymer is a material having excellent electrooptic effect as the hyperpolarizability increases, and it can be known through the reference of "Dr. Myung-Hyun Lee's nonlinear optical device," and the structural formula It can be represented as a material having properties.

Here, D is electron donors, A is electron acceptors, and the conjugation bridge represents a long p-electron bridge.
Such an electro-optic polymer material is a polymer containing a unit of the structural characteristic in a molecular structure, and the electron transfer from the electron donor to the electron acceptor through the nucleus structure is efficiently performed, thereby increasing the nonlinear characteristic value of the electro-optic polymer. As a result, when a voltage is applied to the transparent electrode 17 and the metal film 13, the refractive index of the material changes.

As another feature of the present invention, a fine diffraction grating 21 structure is formed at the interface between the metal film 13 and the electro-optic material film 15. By using this structure, the diffraction grating surface plasmon resonance can be realized. That is, the light incident on the interface between the periodically changing metal film 13 and the electro-optic material film 15 is diffracted at various angles. The higher-order diffraction beam is selected by appropriately selecting the incident angle, wavelength, voltage, and diffraction grating structure. The wave vector of can be matched to the wave vector (k _sp ) of the surface plasmon wave.

Where k _o is the wave vector of incident light, ε _metal , and ε _diel are the dielectric constants of the metal film 13 and the electro-optic material film 15, k _g is (2π) / Λ (lattice pitch interval), and θ is the angle of incidence Indicates. As can be seen from Equation 1, the diffraction grating coupling surface plasmon resonance phenomenon depends on the refractive index of the electro-optic film 15, the wavelength and angle of the incident light, and the structure of the diffraction grating.

As a manufacturing method for realizing such an optical modulation device, in particular, the optical modulation chip 10, as shown in Figure 3, the first deposition step of depositing a metal film 13 on the upper surface of the substrate 11; A second deposition step of forming a diffraction grating 21 by installing a pattern mask in front of the metal film 13 and depositing metal again; In addition, the electro-optic material film 15 and the transparent electrode 17 are sequentially stacked on the diffraction grating 21.

The substrate 11 is formed of a material such as polymer, metal, ceramic, etc., and uses a flat top surface.

The metal film 13 is formed using a single metal or an alloy such as gold, silver, copper, aluminum, etc., which is easy to discharge charged particles by an external magnetic pole and has a negative dielectric constant. The metal film may be formed in a single layer or multiple layers.

In addition, the electro-optic material film 15 uses an electro-optic material whose refractive index is changed by applied voltage. For example, an electro-optic inorganic material such as electro-optic polymer, liquid crystal, LiNbO ₃ or PMN-PT is used. To prepare.

In addition, the transparent electrode 17 is formed of an ITO electrode or a plastic electrode.

Referring to the operation of the present invention implemented by such a manufacturing method as follows.

Basically, the optical modulator of the present invention provides a system for observing a surface plasmon phenomenon using a diffraction grating having a fine period.

More specifically, in the present invention, the p-polarized light emitted from the light source unit 30 is incident in the direction of the transparent electrode 17. First, the angle at which the intensity of the reflected light is minimized while changing the incident angle, that is, the surface plasmon resonance angle (θ _SPR ) is determined. After the incident light is fixed at this angle θ _SPR , light modulation is performed by adjusting the voltage of the power source 19 applied to the metal film 13 and the transparent electrode 17. When the refractive index of the electro-optic film 15 is changed by the voltage, the surface plasmon resonance condition is changed, so that the intensity of the reflected light is modulated.

As another embodiment, in the present invention, the wavelength can be selected using the properties of the surface plasmon resonance condition depending on the refractive index, the wavelength, and the diffraction grating of the electro-optic material film 15. Accordingly, when light having a wavelength of λ ₁ satisfies the surface plasmon resonance condition, when the voltage V ₁ is applied, only light having a wavelength of λ ₁ is absorbed and light having a wavelength of λ ₂ is passed, thereby enabling wavelength selection. On the contrary, when voltage V ₂ is applied, only light having a wavelength of λ ₂ is absorbed and light having a wavelength of λ ₁ passes.

As another embodiment of the present invention, Fig. 4 shows a structure in which the diffraction grating 21 is formed of multiple units 21a, 21b, 21c and 21d having different lattice periods. At this time, the diffraction gratings 21a, 21b, 21c, and 21d have different lattice periods, so that only one wavelength of each of the wavelengths constituting the light source is selectively absorbed, and the remaining wavelengths are allowed to pass. .

In the manufacturing method of this embodiment, as shown in FIG. 5, after the first deposition step is completed, a plurality of pattern masks having different lattice cycles are provided in front of the metal film 13, and the metal is deposited to form a diffraction grating 21a. (21b) (21c) and 21d are formed.

6 shows another embodiment of the present invention. As can be seen from the drawings, the surface plasmon resonance optical modulation chip 10 of the present invention includes a substrate 11 constituting a base, a metal unit 13, a diffraction grating 21, and an electro-optic material film of a plurality of units. And transparent electrodes are sequentially stacked.

To this end, in the manufacturing method of the present invention, as shown in Figure 7, the first deposition step of depositing a metal by installing a basic mask in front of the substrate 11 to form a plurality of units of the metal film 13; A second deposition step of forming a plurality of diffraction gratings 21 by installing a pattern mask in front of the plurality of unit metal films 13 and depositing metal again; And sequentially stacking an electro-optic material film and a transparent electrode on the substrate and the diffraction grating.

8 shows an embodiment in which multiple diffraction grating units 21a, 21b, 21c and 21d are formed on the metal film 13 of the plurality of units, respectively. To this end, in the present invention, as shown in FIG. 9, after the first deposition step of forming the plurality of units of the metal film 13 is completed, a plurality of pattern masks having different lattice periods are provided in front of each metal film 13. The metal is deposited to form diffraction gratings 21a, 21b, 21c and 21d.

As can be seen through the embodiments of the present invention described above, the manufacturing method of the optical modulator of the present invention easily implements a single, multiple and multiple diffraction gratings at the interface between the metal film and the dielectric using a pattern mask. You can get the effect.

Therefore, according to the present invention, it is possible to solve the problems of the conventional method using a high refractive prism, and to implement an optical modulation system using micro-diffraction grating surface plasmon resonance.

In addition, according to the present invention, compared to the Kretschmann-type surface plasmon light modulator that requires a high refractive prism, it is possible to achieve the effect of simplifying, miniaturization, high integration, and mass production easily at a low manufacturing cost.

This technology of the present invention can be used in the manufacture of ultra-high speed optical switches, optical modulators, space-optic modulators, optical interconnects, optical filters, displays, and can be widely applied to manufacturing various components in the optical communication and information electronic fields.

Claims (6)

A first deposition step of depositing a metal film on an upper surface of the substrate; A second deposition step of installing a pattern mask in front of the metal film and depositing a metal to form a diffraction grating; Sequentially forming an electro-optic material film and a transparent electrode on the diffraction grating; And And the electro-optic material film is formed of an electro-optic polymer material having a refractive index that is changed by a Pockels effect and a surface plasmon resonance condition when a voltage is applied to the metal film and the transparent electrode. The method of claim 1, wherein the metal is a single metal or an alloy such as gold, silver, copper, aluminum, or the like. The method of claim 1, wherein the electro-optic material film is laminated using an electro-optic inorganic material. The method of claim 1, wherein the diffraction grating is formed into multiple units having different lattice periods. Installing a mask in front of the substrate and depositing a metal to form a plurality of units of a metal film; A second deposition step of forming a plurality of diffraction gratings by installing a pattern mask in front of the plurality of unit metal films and depositing metal again; And And sequentially stacking an electro-optic material film and a transparent electrode on the substrate and the diffraction grating. The method of manufacturing an optical modulator according to claim 5, wherein each of the diffraction gratings is formed to have a different lattice period.

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