KR102139639B1 - GRAPHENE TRANSPARENT ELECTRODE AND LCoS BASED WAVELENGTH SELECTIVE SWITCH COMPRISING THE SAME - Google Patents

Abstract

The present invention not only has excellent light transmittance in both the visible light region and the infrared region, but also has a markedly improved light transmittance in the infrared region compared to the visible light region, so that graphene can significantly improve the light output of devices used for optical communication in the infrared wavelength band. Provides a wavelength selection switch based on a transparent electrode and a silicon liquid crystal device including the same.

Description

GRAPHENE TRANSPARENT ELECTRODE AND LCoS BASED WAVELENGTH SELECTIVE SWITCH COMPRISING THE SAME using a graphene transparent electrode and a silicon liquid crystal device containing the same

The present invention relates to a graphene transparent electrode and a silicon liquid crystal device-based wavelength selection switch including the same, specifically having excellent light transmittance in the visible light region and at the same time, having improved light transmittance in the infrared region and used for optical communication in the infrared wavelength band. It relates to a graphene transparent electrode capable of significantly improving the light output of the device and a wavelength selection switch based on a silicon liquid crystal device including the same.

Optical networks use a wavelength selective switch (WSS) to dynamically route optical wavelength signals from a source to a destination. Specifically, a wavelength selection switch (WSS) is required to transmit a large amount of information through a single optical fiber as a multi-wavelength signal through optical communication, and to transmit a signal of a specific wavelength from an input signal composed of multiple wavelengths to an arbitrary output port. will be.

Previously, a microelectromechanical (MEMS) mirror-based wavelength selection switch was developed, but recently, a liquid crystal on silicon (LCoS) device-based wavelength selection switch has excellent port scalability and is advantageous for alignment, etc. Because of this, it is emerging as a new technology.

The liquid crystal on silicon (LCoS) device includes a liquid crystal material interposed between a transparent electrode layer having a transparent electrode and a silicon substrate divided into a two-dimensional array of individually addressable pixels. Specifically, the incident light to the wavelength selection switch based on the silicon liquid crystal element is adjusted through a differential phase delay, which is performed by a complementary metal-oxide semiconductor (CMOS) backplane and a liquid crystal layer. For this, a transparent electrode layer is required as a common electrode. In order to minimize the loss of the amount of light used for optical communication, the transparent electrode needs a transparent property in the infrared wavelength band, and the light transmittance of the transparent electrode layer has an important effect on the intensity of reflected light.

Specifically, Korean Patent Publication No. 2003-0062886 discloses a silicon liquid crystal device-based wavelength selection switch using indiumtin-oxide (ITO), a transparent electrode material, which is currently used as a transparent electrode. The silicon-based liquid crystal device-based wavelength selection switch using indium-tin oxide (ITO) as a transparent electrode satisfies the transparent properties in the visible light region of the 400-700 nm wavelength range, while the transparent properties and the light transmittance rapidly in the infrared wavelength range of 1500 nm or more. Accordingly, there is a problem in that the light output of the device used for optical communication in the infrared wavelength band is significantly reduced. In addition, in order to use indium tin oxide (ITO) as a transparent electrode in the infrared wavelength band, since the transmittance must be improved through additional thin film deposition, the manufacturing cost of the transparent electrode increases due to the introduction of an additional process, which makes it difficult to commercialize.

Korea Patent Publication 2003-0062886

The present invention has been devised to solve the above-mentioned problems, and the first problem to be solved by the present invention is to have an excellent light transmittance in the visible light region and at the same time have an improved light transmittance in the infrared region, and is used for optical communication in the infrared wavelength band. It is to provide a graphene transparent electrode and a silicon-based liquid crystal device-based wavelength selection switch that can significantly improve the light output of the.

In addition, the second problem to be solved by the present invention is to provide a graphene transparent electrode that has a low sheet resistance value in the infrared region and can maintain transparent properties by using only a simple process. It is to provide a wavelength selection switch based on a silicon liquid crystal device.

In order to solve the above-described problems, the present invention includes a substrate and at least one layer of graphene transferred on the substrate, wherein the graphene has a light transmittance of 98% or more in a wavelength range of 1500 to 1700 nm when the sheet resistance is 400 Ω/sq or less. It provides a graphene transparent electrode, characterized in that having a.

According to one preferred embodiment of the present invention, the graphene may satisfy both of the following conditions (a) and (b).

(a) The light transmittance in the wavelength range of 1500~1700nm should be higher than the light transmittance in the wavelength range of 500~700nm.

(b) The graphene should have a light transmittance of 100% or more in a wavelength range of 1500 to 1700 nm when the sheet resistance is 400 Ω/sq or less.

According to another preferred embodiment of the present invention, the graphene may further satisfy the following condition (c).

(c) The following relational expression 1 should be satisfied.

[Relationship 1]

T ₁₅₀₀ -T ₅₅₀ ≥2.0 (%)

(T ₁₅₀₀ : Light transmittance of graphene in the wavelength band of 1500 nm (%), T ₅₅₀ : Light transmittance of graphene in the wavelength band of ₅₅₀ nm (%))

In addition, the present invention is a wavelength selection switch using a silicon liquid crystal element having a liquid crystal layer formed between a silicon backplane layer and a glass substrate layer, a reflective layer pixel electrode formed between the silicon backplane layer and the liquid crystal layer to cause light modulation; and It provides a wavelength selection switch using a silicon liquid crystal device comprising: a graphene transparent electrode of any one of claims 1 to 3 formed between the liquid crystal layer and the glass substrate layer.

According to a preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device may have a light reflectance of 72% or more in all wavelength bands of 1000 to 1600 nm.

According to another preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device may have a light reflectivity of 80% or more in all wavelength bands of 1500 to 1600 nm.

According to another preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device may satisfy both of the following conditions (d) and (e).

(d) R _G in the wavelength range of 1000~1400nm ≤ R _I

(e) R _G in the wavelength range from 1500 to 1600 nm ≥ R _I

(R _G : Light reflectance (%) of the wavelength selection switch using the silicon liquid crystal element _I : Light reflectance (%) when using indium-tin oxide (ITO) instead of graphene as a transparent electrode included in the wavelength selection switch using the silicon liquid crystal element

According to another preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device may satisfy the following Equation 2 in the wavelength range of 1530 ~ 1565nm.

[Relationship 2]

1.7 ≤ (R _{G -} R _I )/R _I ×100 ≤ 4.0

(R _G : Light reflectance (%) of wavelength selection switch using silicon liquid crystal element using graphene transparent electrode, R _I : Light reflectance (%) of wavelength selection switch using silicon liquid crystal element using indium-tin oxide (ITO) transparent electrode )

Hereinafter, terms used in the present invention will be briefly described.

The term "graphene" means that a plurality of carbon atoms are covalently linked to each other to form a two-dimensional film (usually sp2 bond). Carbon atoms constituting graphene form a 6-membered ring as a basic repeating unit, but it is also possible to further include a 5-membered ring and/or a 7-membered ring. Depending on the content of the 5-membered ring and/or 7-membered ring that may be included in the graphene, the shape of the graphene may be changed. Graphene may be made of a single layer, but it is also possible that they are stacked to form a plurality of layers, and may be up to 100 nm thick.

The present invention not only has excellent light transmittance in both the visible light region and the infrared region, but also has a markedly improved light transmittance in the infrared region compared to the visible light region, so that graphene can significantly improve the light output of devices used for optical communication in the infrared wavelength band. Provides a wavelength selection switch based on a transparent electrode and a silicon liquid crystal device including the same.

In addition, the present invention has a low sheet resistance value in the infrared region and can maintain the transparent properties at the same time, and can be utilized as an infrared imaging, infrared sensor, infrared emitter, graphene transparent electrode, and a silicon liquid crystal device-based wavelength selection switch including the same Provides

1 is a graph of transmittance of graphene according to an exemplary embodiment of the present invention.
2 is a structural diagram of a wavelength selection switch based on a silicon liquid crystal device according to an exemplary embodiment of the present invention.
3 is an optical wavelength band classification table.
4 is a graph of reflectance of a wavelength selection switch based on a silicon liquid crystal device according to an exemplary embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily practice.

As described above, a wavelength selection switch based on a silicon liquid crystal device using a conventional indium-tin oxide (ITO) as a transparent electrode satisfies the transparent property in the visible light region of the 400-700 nm wavelength range, while the infrared wavelength range of 1500 nm or more In, there is a problem in that the transparent properties and the light transmittance are sharply reduced, and accordingly, the light output of the device used for optical communication in the infrared wavelength band is significantly reduced. In addition, in order to use indium tin oxide (ITO) as a transparent electrode in the infrared wavelength band, since the transmittance must be improved through additional thin film deposition, the manufacturing cost of the transparent electrode increases due to the introduction of an additional process, which makes it difficult to commercialize.

Accordingly, the present invention includes a substrate and at least one layer of graphene transferred on the substrate, wherein the graphene has a light transmittance of 98% or more in a wavelength range of 1500 to 1700 nm when the sheet resistance is 400 Ω/sq or less. By providing a pin transparent electrode, a solution to the above-described problem was sought.

Through this, the present invention not only has excellent light transmittance in both the visible light region and the infrared region, but also has a significantly improved light transmittance in the infrared region compared to the visible light region, thereby significantly improving the light output of a device used for optical communication in the infrared wavelength band. have. In addition, the present invention has an advantage that can be used in various fields such as infrared imaging, infrared sensors, infrared emitters, etc., since it has a low sheet resistance value in the infrared region and can maintain transparent properties.

First, the substrate will be described. The substrate may include at least one layer of graphene transferred on the substrate, and is not limited as long as it can be used in the art, but preferably, a flat material may be used as a transparent material, and more preferably PET (polyethylene terephthalate), glass (glass), quartz (quartz), sapphire (sapphire), or a wafer (wafer) can be used, flexible (flexible) material can also be used.

Next, the graphene included in the graphene transparent electrode of the present invention will be described.

The graphene is a carbon nanomaterial having a two-dimensional planar structure composed of a monoatomic layer formed of strong covalent bonds of carbon atoms, and has high charge mobility, thermal conductivity, and excellent chemical resistance properties. In addition, the single layer thickness of the graphene may be about 0.25 to 0.35 nm because it is only one carbon atom. The graphene has metallic properties, has conductivity in a layer direction, and has high mobility of charge carriers, thereby realizing a high-speed electronic device. The graphene has excellent mechanical robustness and chemical stability, has properties of both semiconductor and conductor, and has a small thickness, and thus has great applicability to flat panel display devices, transistors, energy storage devices, and nano-sized electronic devices. When the graphene is used, it is easy to manufacture a device using semiconductor process technology, and particularly, there is an advantage of easy integration of a large area.

The present invention provides a graphene transparent electrode using such graphene, and the graphene included in the present invention has a sheet resistance of 400 Ω/sq or less, and when the sheet resistance range is satisfied, light transmittance is 98% or more in a wavelength range of 1500 to 1700 nm. to be. Preferably, when the sheet resistance of the graphene is 350 Ω/sq or less, it may have a light transmittance of 99% or more in a wavelength range of 1500 to 1700 nm, and more preferably, when the sheet resistance of the graphene is 300 Ω/sq or less, a wavelength range of 1500 to 1700 nm In can have a light transmittance of 100% or more. In general, the optical conductivity of graphene is known to be a constant value in a wide wavelength range, but when doping through an increase in the charge density on the graphene surface, it is possible to suppress the optical conductivity in the infrared region. When the optical conductivity is low, the amount of light absorbed at the infrared wavelength decreases, and thus the transmittance increases in the infrared region.

It is generally known that the optical conductivity of graphene has a constant value in a wide wavelength range. However, according to the present invention, doping through an increase in the charge density on the graphene surface is performed to suppress optical conductivity in the infrared region, and accordingly, the amount of light absorbed in the infrared wavelength is reduced, thereby improving the transmittance in the infrared region. have.

Accordingly, the graphene of the present invention has a low sheet resistance value in the wavelength range of 1500 to 1700 nm, which is an infrared region, and at the same time has a remarkably improved light transmittance, and has a value of nearly 100% transmittance in the wavelength range of 1500 to 1700 nm, and thus other transparent electrodes. It has the effect of retaining excellent optical properties compared to the material.

In this regard, FIG. 1 is a graph of transmittance of graphene according to a preferred embodiment of the present invention. Referring to the graph, it can be seen that the graphene included in the present invention has significantly improved transmittance in a wavelength range of 1500 nm or more. That is, the transmittance of only graphene of the present invention has a high value of 96.6% at 550 nm, and at the same time, it has a high value of 100.8% at 1500 nm, and thus it can be confirmed that the transmittance is significantly improved in the infrared region. In addition, it can be seen that even in the region of 1500 nm or more, the total transmittance of graphene and PET decreases little by little and rapidly decreases at 2000 nm or more. On the other hand, the transmittance of only the graphene of the present invention shows a stable high value at 1500 nm or more, which is maintained even in the region of 2000 nm or more, and it can be confirmed that the graphene of the present invention has an effect of having excellent transmittance over the entire wavelength range. .

The graphene transparent electrode can be used in various applications depending on the conduction characteristics. The graphene of the present invention should have a sheet resistance of 400 Ω/sq or less. If the sheet resistance of the graphene exceeds 400 Ω/sq, the light transmittance is significantly lower than 96% in the wavelength range of 1500 to 1700 nm, and a problem that is difficult to use as a transparent electrode may occur.

In addition, if the light transmittance is less than 96% in the wavelength range of 1500 to 1700 nm in the infrared region, graphene is difficult to maintain transparent properties in the wavelength band, and accordingly, it is difficult to minimize the loss of the amount of light used in optical communication. This can happen. As a result, light loss occurs while the incident light is transmitted through the transparent electrode layer, which may cause a problem that the intensity of the reflected light is significantly lowered.

According to one preferred embodiment of the present invention, the graphene may satisfy both of the following conditions (a) and (b).

(a) The light transmittance in the wavelength range of 1500~1700nm should be higher than the light transmittance in the wavelength range of 500~700nm.

(b) The graphene should have a light transmittance of 100% or more in a wavelength range of 1500 to 1700 nm when the sheet resistance is 400 Ω/sq or less.

The graphene included in the present invention has better light transmittance in the wavelength range of 1500 to 1700 nm, which is the infrared region, than light transmittance in the wavelength range of 500 to 700 nm, which is the visible light region. In addition, in the infrared wavelength range of 1500 to 1700 nm, when the sheet resistance is 400 Ω/sq or less, a remarkably high light transmittance of 100% or more can be satisfied. Accordingly, the present invention not only has excellent light transmittance in both the visible light region and the infrared region, but also has a significantly improved light transmittance in the infrared region compared to the visible light region, thereby significantly improving the light output of a device used for optical communication in the infrared wavelength band. It has an effect.

In addition, the graphene may further satisfy the following condition (c).

(c) The following relational expression 1 should be satisfied.

[Relationship 1]

T ₁₅₀₀ -T ₅₅₀ ≥ 2.0 (%)

(T ₁₅₀₀ : Light transmittance of graphene in the wavelength range of 1500 nm (%), T ₅₅₀ : Light transmittance of graphene in the wavelength range of ₅₅₀ nm (%))

In the graphene of the present invention, the light transmittance (T ₁₅₀₀ ) in the wavelength band of ₁₅₀₀ nm may be 2% or more higher than the light transmittance (T ₅₅₀ ) in the wavelength band of 550 nm. If the T ₁₅₀₀ -T ₅₅₀ is less than 2%, the transparent properties of the transparent electrode in the infrared wavelength band rapidly decrease, and the loss of the amount of light generated by the transparent electrode occurs, so the intensity of the reflected light is lowered, which is not suitable for the optical communication field. Can occur.

In addition, the present invention is a wavelength selection switch using a silicon liquid crystal element having a liquid crystal layer formed between a silicon backplane layer and a glass substrate layer, a reflective layer pixel electrode formed between the silicon backplane layer and the liquid crystal layer to cause light modulation; And a graphene transparent electrode formed between the liquid crystal layer and the glass substrate layer. Accordingly, not only has excellent light transmittance in both the visible light region and the infrared region, but in the infrared region, graphene is transparent, which has significantly improved light transmittance compared to the visible light region, and can significantly improve the light output of devices used for optical communication in the infrared wavelength band. There is an effect that can provide a wavelength selection switch based on a silicon liquid crystal device including an electrode. In addition, since it has a low sheet resistance value in the infrared region and can maintain transparent properties, it can be used in various ways as infrared imaging, infrared sensors, and infrared emitters.

First, the liquid crystal on silicon (LCoS) device used in the present invention will be described. Silicon liquid crystal device uses the diffraction phenomenon of light to control the direction of incident light from the reflector located in each pixel. It has no moving parts, so it is resistant to vibration, has excellent port expandability and robustness, compensates for loss for each channel, compensates for wavelength displacement, It has the advantage of being able to easily perform the functions of I/O channel monitoring. The silicon liquid crystal device is manufactured in a reflective type by configuring a pixel electrode on a silicon backplane.

In the silicon liquid crystal device, a liquid crystal layer is formed between a silicon backplane layer and a glass substrate layer. The silicon backplane layer is a silicon wafer substrate, the glass substrate layer constitutes a touch portion of the device, and a liquid crystal layer is injected between the silicon backplane layer and the glass substrate layer to form a liquid crystal on silicon (LCoS), which is an ultra-small display device. ) Make up the device.

Arbitrary angles according to a specific image pattern displayed in a liquid crystal on silicon (LCoS) device region where an incident optical signal touches by using a characteristic in which the phase state of the liquid crystal layer changes according to the voltage applied to both ends of the liquid crystal layer. It serves to deflect the incident light and reflect it. In general, the diameter of the input optical signal is larger than the size of a single pixel, and thus the optical signal is reflected through multiple pixels. The wavelength selection switch based on the liquid crystal on silicon (LCoS) device of the present invention, each wavelength incident light is incident on the silicon liquid crystal device according to the image pattern displayed on the liquid crystal (liquid crystal on silicon, LCoS) device Reflects at different angles.

In addition, between the silicon backplane layer and the liquid crystal layer, a reflective layer pixel electrode causing light modulation is formed. The reflective layer pixel electrode may be used for optical communication by changing the intensity of the input light to induce light modulation carrying a signal on the light. The reflective layer pixel electrode may be an electrode commonly used in the art, and preferably an aluminum reflective electrode.

In this regard, FIG. 2 is a structural diagram of a wavelength selection switch based on a silicon liquid crystal device according to an exemplary embodiment of the present invention. Referring to the drawings, a liquid crystal layer exists between the silicon backplane layer and the glass substrate layer, and a reflective layer pixel electrode is formed between the silicon backplane layer and the glass substrate layer. In addition, since the graphene transparent electrode is formed between the glass substrate layer and the liquid crystal layer, it can be seen that when the light is incident, the graphene transparent electrode passes twice. Therefore, in order to minimize the loss of light quantity, it is necessary for the graphene transparent electrode to maintain a transparent property in the infrared wavelength band, and the transmittance of the transparent electrode has a significant effect on the intensity of reflected light, so that the graphene transparent electrode needs excellent transmittance. can confirm.

Meanwhile, any one of the graphene transparent electrodes of the present invention described above may be formed between the liquid crystal layer and the glass substrate layer to configure a wavelength selection switch using a silicon liquid crystal element. Through this, not only has excellent light transmittance in both the visible light region and the infrared region, but also has a significantly improved light transmittance in the infrared region compared to the visible light region, which can significantly improve the light output of devices used for optical communication in the infrared wavelength band. It is possible to provide a device-based wavelength selection switch. Accordingly, the present invention has an advantage that can be used in various ways, such as infrared imaging, infrared sensors, infrared emitters.

The wavelength selection switch using the silicon liquid crystal device of the present invention may have a light reflectance of 72% or more in all wavelength bands of 1000 to 1600 nm, and more preferably, a light reflectance of 80% or more in all wavelength bands of 1500 to 1600 nm. That is, according to a preferred embodiment of the present invention, the light reflectivity may be 72% or more at all wavelengths belonging to the range of 1000 to 1600 nm, and at the same time, the light reflectance at all wavelengths belonging to the range of 1500 to 1600 nm may be 80% or more.

According to one preferred embodiment of the present invention, the wavelength selection switch using the silicon liquid crystal device of the present invention may satisfy both of the following conditions (d) and (e).

(d) R _G in the wavelength range of 1000~1400nm ≤ R _I

(e) R _G in the wavelength range from 1500 to 1600 nm ≥ R _I

(R _G : Light reflectance (%) of wavelength selection switch using silicon liquid crystal element using graphene transparent electrode, R _I : Light reflectance (%) of wavelength selection switch using silicon liquid crystal element using indium-tin oxide (ITO) transparent electrode )

At this time, the R _G means the light reflectivity of the wavelength selection switch using the silicon liquid crystal element of the present invention described above, R _I is the liquid crystal layer and the glass substrate included in the wavelength selection switch using the silicon liquid crystal element of the present invention It means the light reflectance when using indium-tin oxide (ITO) commonly used in the art instead of the graphene transparent electrode formed between the layers.

Through this, the present invention can provide a wavelength selection switch using a silicon liquid crystal element suitable for an infrared region of 1500 to 1600 nm wavelength band, and has an advantage that can be utilized in various technical fields using infrared such as infrared imaging, infrared sensor, and infrared emitter. .

Meanwhile, FIG. 3 is an optical wavelength band classification table, and according to the IUT-T (International Telecommunication Union-Telecommunication Standardization Sector) optical wavelength band classification, C band (1530 nm to 1565 nm), L band (1565 nm to 1625 nm) and U for medium and long distance transmission A light source having a wavelength in the band (1625nm to 1675nm) is used. Among them, the C band is a low-loss band used for medium to long distance transmission, and there is a need to improve the light output of the device used for optical communication by improving light transmittance in the wavelength band.

Accordingly, the present invention provides a wavelength selection switch using a silicon liquid crystal device having a significantly improved light reflectivity in the C band, that is, 1530nm to 1565nm wavelength band, used in optical communication. In this regard, according to a preferred embodiment of the present invention,

The wavelength selection switch using the silicon liquid crystal device of the present invention may satisfy the following Equation 2 in the wavelength range of 1530 to 1565 nm.

[Relationship 2]

1.7 ≤ (R _{G -} R _I )/R _I ×100 ≤ 4.0

(R _G : Light reflectance (%) of the wavelength selection switch using the silicon liquid crystal element, R _I : Light when using indium-tin oxide (ITO) instead of graphene as a transparent electrode included in the wavelength selection switch using the silicon liquid crystal element reflectivity(%))

The relational expression 2 may preferably be 1.7 ≤ (R _{G -} R _I )/R _I ×100 ≤ 3.8, and more preferably 1.7 ≤ (R _{G -} R _I )/R _I ×100 ≤ 3.6. .

Through this, the present invention has an effect of providing a wavelength selection switch using a silicon liquid crystal device suitable for use in a corresponding wavelength region because the light reflectance in the C band region is remarkably excellent.

Specifically, FIG. 4 is a graph of reflectivity of a wavelength selection switch based on a silicon liquid crystal device according to an exemplary embodiment of the present invention. Referring to the graph, it can be seen that the wavelength selection switch using a silicon liquid crystal element including the graphene transparent electrode of the present invention has a remarkably high reflectance in a wavelength range of 1500 to 1600 nm, and can be utilized in various technical fields using infrared rays. .

As a result, the wavelength selection switch using the graphene transparent electrode of the present invention and a silicon liquid crystal device including the same has excellent light transmittance in the visible light region and has improved light transmittance in the infrared region. Since the light output can be significantly improved, it can be utilized in various technical fields using infrared, such as infrared imaging, infrared sensors, and infrared emitters.

Hereinafter, the present invention will be described in more detail through specific examples.

Example One

The 35°C Cu plate was charged by CVD. CH ₄ was flowed in the furnace at a rate of 30 sccm for about 5 minutes at about 1000°C. Then, under H ₂ atmosphere, cooling was performed at a rate of 60° C./min to 600° C. and at a rate of 40° C./min to room temperature to form graphene on Cu. The stack of Cu and graphene was immersed in a 4 wt% aqueous solution of (NH ₄ )S 2 O 8 for 120 minutes to remove Cu. The graphene thus obtained was immersed in a composition containing 3 wt% of 1,2,4-benzotriazine, 3 wt% of H ₂ O ₂ , 9 wt% of H ₂ SO ₄ and the remainder for 40 minutes. Doped graphene was obtained. A graphene transparent electrode provided on a glass substrate using the doped graphene was prepared. Next, a reflective layer pixel electrode was provided on the silicon backplane layer, and a sealing material was applied. Then, a liquid crystal layer was formed by applying a liquid crystal. A graphene transparent electrode formed on a glass substrate layer was laminated on the liquid crystal layer, and the sealing material was cured to prepare a wavelength selection switch using a silicon liquid crystal element.

Comparative example One

It was carried out in the same manner as in Example 1, except that an indium-tin oxide (ITO) electrode was used instead of the graphene transparent electrode.

Experimental Example 1. Reflectance measurement

The reflectivity of the wavelength selection switch using the silicon liquid crystal device manufactured through Example 1 and Comparative Example 1 was measured, and the results are shown in the graphs of Tables 1 and 4 below. The increase rate of the reflectance in Table 1 is shown by rounding to the second decimal place.

Table 1

Referring to Table 1, it can be seen that Example 1 including the graphene transparent electrode of the present invention has significantly better reflectance than Comparative Example 1. In particular, at 1500nm or more, it shows a remarkably good increase rate, and at 1565nm, it shows a high increase rate of 3.49%, which confirms that the reflectance of the present invention is remarkably excellent.

Claims (8)

delete delete delete In the wavelength selection switch using a silicon liquid crystal element is a liquid crystal layer is formed between the silicon backplane layer and the glass substrate layer,
A reflective layer pixel electrode formed between an upper surface of the silicon backplane layer and a lower portion of the liquid crystal layer to cause light modulation; And
A graphene transparent electrode formed between the upper portion of the liquid crystal layer and the lower surface of the glass substrate layer, and comprising a substrate and one or more graphene transferred on the substrate
Including,
When the sheet resistance is 400Ω/sq or less, the graphene is 98% or more in the wavelength range of 1500 to 1700nm, and the light transmittance in the wavelength range of 1500 to 1700nm is higher than the light transmittance in the wavelength range of 500 to 700nm,
The incident light passing through the glass substrate layer, the graphene transparent electrode, and the liquid crystal layer in turn is reflected by the reflective layer pixel electrode, and passes through the liquid crystal layer, the graphene transparent electrode, and the glass substrate layer in turn to reflect light. Output,
The light reflectance of the reflected light to the incident light is 72.9% to 78.2% in the wavelength range of 1000 to 1400 nm, and 80.2% to 83.7% in the wavelength range of 1500 to 1600 nm,
In the wavelength range of 1000 to 1600 nm, the rate of change of the light reflectivity between 1200 nm and 1300 nm is greater than the rate of change of the light reflectivity when changing in units of 100 nm in the remaining wavelength bands
Wavelength selection switch using silicon liquid crystal element.
delete delete According to claim 4,
Wavelength selection switch using a silicon liquid crystal device, characterized in that both of the following conditions (d) and (e) are satisfied.
(d) R _G in the wavelength range of 1000~1400nm ≤ R _I
(e) R _G in the wavelength range from 1500 to 1600 nm ≥ R _I
(R _G : Light reflectance (%) of the wavelength selection switch using the silicon liquid crystal element, R _I : Light when using indium-tin oxide (ITO) instead of graphene as a transparent electrode included in the wavelength selection switch using the silicon liquid crystal element reflectivity(%))
According to claim 4,
Wavelength selection switch using a silicon liquid crystal device, characterized in that satisfies the following relationship 2 in the wavelength range of 1530 ~ 1565nm.
[Relationship 2]
1.7 ≤ (R _{G -} R _I )/R _I ×100 ≤ 4.0
(R _G : Light reflectance (%) of wavelength selection switch using silicon liquid crystal element using graphene transparent electrode, R _I : Light reflectance (%) of wavelength selection switch using silicon liquid crystal element using indium-tin oxide (ITO) transparent electrode )

Images