Near-infrared bandpass filter

Abstract

The present invention relates to a near-infrared band transmission filter comprising: metal reflective layers spaced apart from each other in a first direction; a cavity layer interposed between the metal reflective layers; and light absorption layers spaced apart from each other in the first direction within the cavity layer, wherein the light absorption layers can absorb visible light or ultraviolet light.

Description

Technology Field

[0001] The present invention relates to a near-infrared band transmission filter, and more specifically, to a near-infrared band transmission filter with improved out-of-band blocking characteristics. Background Technology

[0002] Near-infrared (NIR) transmission filters are optical filters that selectively transmit only specific wavelengths of near-infrared light (NIR) while reflecting or absorbing light of other wavelengths. These filters are essential in various optical and electronic devices that utilize the near-infrared band and have established themselves as a critical technology in multiple fields, including industry, medicine, environment, and military.

[0003] Near-infrared light is located in the visible light range of the electromagnetic spectrum and is useful for analyzing the chemical composition or thermal properties of materials. To maximize the utility of this near-infrared band, near-infrared transmission filters are used, and these filters play a key role in various applications requiring high accuracy by transmitting only specific wavelengths.

[0004] Current technical challenges related to near-infrared band transmission filters include achieving high transmittance over a wide bandwidth, meeting the requirements for miniaturization and lightweighting, controlling signal noise, and lowering manufacturing costs. In particular, applications such as wearable devices and micro-sensors require technological advancements that maintain performance while reducing the size and weight of the filter. The problem to be solved

[0005] The problem that the present invention aims to solve is to provide a near-infrared band transmission filter with improved out-of-band blocking characteristics.

[0006] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0007] A near-infrared band transmission filter according to the concept of the present invention comprises: metal reflective layers spaced apart from each other in a first direction; a cavity layer interposed between the metal reflective layers; and light absorption layers spaced apart from each other in the first direction within the cavity layer, wherein the light absorption layers can absorb visible light or ultraviolet light. Effects of the invention

[0008] A near-infrared band transmission filter according to the concept of the present invention can absorb stopband signal noise by additionally placing a short-wavelength light absorption layer at a point where the stopband signal noise, which is not eliminated by resonance, is maximum within a dielectric cavity filling the space between mutually opposing metal reflection layers. As a result, the near-infrared band transmission filter with the short-wavelength light absorption layer can have its out-of-band blocking characteristics further improved. Brief explanation of the drawing

[0009] FIG. 1 is a cross-sectional view showing a near-infrared band transmission filter according to one embodiment of the present invention. Figure 2 is experimental data to explain the transmission wavelength of a near-infrared band transmission filter according to one comparative example. Figure 3 is experimental data for explaining the transmission wavelength of a near-infrared band transmission filter according to one embodiment of the present invention. Figure 4 is experimental data for explaining the transmittance of a near-infrared band transmission filter according to one embodiment of the present invention according to the light angle. Figure 5 is experimental data for explaining the relative strength of the first-order signal of a near-infrared band transmission filter according to one embodiment of the present invention. Figure 6 is experimental data for explaining the relative strength of a third-order signal of a near-infrared band transmission filter according to one embodiment of the present invention. FIG. 7 is experimental data for explaining the relative strength of the 5th order signal of a near-infrared band transmission filter according to one embodiment of the present invention. FIG. 8 is a cross-sectional view showing a near-infrared band transmission filter according to another embodiment of the present invention. Figure 9 is experimental data to explain the transmission wavelength of a near-infrared band transmission filter according to another comparative example. FIG. 10 is experimental data for explaining the transmission wavelength of a near-infrared band transmission filter according to another embodiment of the present invention. Specific details for implementing the invention

[0010] Hereinafter, in order to explain the present invention more specifically, embodiments according to the present invention will be described in more detail with reference to the accompanying drawings. In the accompanying drawings, the components are depicted enlarged compared to their actual size for convenience of explanation, and the proportions of each component may be exaggerated or reduced.

[0011] FIG. 1 is a cross-sectional view showing a near-infrared band transmission filter according to one embodiment of the present invention.

[0012] Referring to FIG. 1, a near-infrared band transmission filter (100) according to one embodiment of the present invention may include metal reflective layers (110), a cavity layer (120), and light absorption layers (130).

[0013] Metal reflective layers (110) may be spaced apart from each other in a first direction (D1) and may extend in a second direction (D2) that intersects the first direction (D1). Metal reflective layers (110) may be arranged vertically facing each other.

[0014] Each of the metal reflective layers (110) may have a first height (H1) in a first direction (D1). For example, the first height (H1) may be 5 nm or more and 100 nm or less.

[0015] The metal reflective layers (110) may include a metal material. For example, the metal reflective layers (110) may include at least one of silver (Ag), gold (Au), aluminum (Al), copper (Cu), titanium (Ti), or a combination thereof.

[0016] A cavity layer (120) may be interposed between the metal reflective layers (110). The cavity layer (120) may extend in a second direction (D2) along the metal reflective layers (110).

[0017] The cavity layer (120) may include a dielectric material. For example, the cavity layer (120) may include at least one of silicon oxide, titanium oxide, yttrium fluoride, tantalum oxide, zinc oxide, zinc sulfide, or a combination thereof.

[0018] Light absorption layers (130) may be provided within the cavity layer (120). The light absorption layers (130) may be spaced apart from each other in a first direction (D1) and may extend in a second direction (D2).

[0019] The light absorption layers (130) may include a lower light absorption layer (130L) and an upper light absorption layer (130H). The lower light absorption layer (130L) and the upper light absorption layer (130H) may be spaced apart from adjacent metal reflective layers (110) in a first direction (D1).

[0020] Each of the lower light absorption layer (130L) and the upper light absorption layer (130H) may have a second height (H2) in the first direction (D1). For example, the second height (H2) may be 5 nm or more and 50 nm or less.

[0021] However, unlike what is described, in other embodiments of the present invention, the length of the lower light absorption layer (130L) in the first direction (D1) may be different from the length of the upper light absorption layer (130H) in the first direction (D1).

[0022] The upper and lower light absorption layers (130H, 130L) may include a material capable of absorbing visible light or ultraviolet light. As an example, the upper and lower light absorption layers (130H, 130L) may include at least one of silicon, germanium, perovskite, cadmium telluride, a visible light absorbing dye, or a combination thereof.

[0023] The metal reflective layers (110) may be spaced apart from each other by a first length (L1) in a first direction (D1). The lower light absorption layer (130L) and the upper light absorption layer (130H) may be spaced apart from each other by a second length (L2) in a first direction (D1). Each of the upper light absorption layer (130H) and the lower light absorption layer (130L) may be spaced apart from adjacent metal reflective layers (110) by a third length (L3) in a first direction (D1).

[0024] The first length (L1) may be longer than the second length (L2), and the second length (L2) may be longer than the third length (L3). In other words, the distance between the light absorption layers (130) may be longer than the distance between the light absorption layers (130) and the adjacent metal reflection layers (110). For example, the first length (L1) may be about 150 nm, the second length (L2) may be about 90 nm, and the third length (L3) may be about 20 nm, but is not limited thereto.

[0025] The near-infrared band transmission filter (100) according to the present invention can perform the function of selectively transmitting only light of a specific wavelength by enhancing light of a specific wavelength and suppressing light of other wavelengths. Metal reflective layers (110) can perform the role of reflecting light within the band transmission filter (100) to form light resonance conditions, cavity layers (120) can perform the role of causing light of a specific wavelength to resonate, and light absorption layers (130) can perform the role of absorbing light of a shorter wavelength than near-infrared.

[0026] For example, the near-infrared band transmission filter (100) according to the present invention may be a Fabry-Perot resonator-based band transmission filter and may remove some of the signal noises through resonance. In this specification, the effective signal may refer to a signal to be transmitted through the near-infrared band transmission filter (100), and the signal noise may refer to a signal to be removed through the near-infrared band transmission filter (100).

[0027] The light absorption layers (130) can serve to absorb signal noise that is not removed through resonance. The wavelength of the signal noise that is not removed through resonance may be 1 / n times the effective signal wavelength (where n is a natural number greater than or equal to 2). The signal noise that is not removed through resonance is a third-order signal (the third in FIGS. 2 and FIGS. 3). rd order), 5th signal (5 of FIGS. 2 and FIGS. 3) th may include a 2n-1 order signal, … , and a 3rd order signal (3 in FIGS. 2 and 3). rd order), 5th signal (5 of FIGS. 2 and FIGS. 3) th The wavelength of each of the 2n-1st order signals can be 1 / n times the effective signal wavelength. 1st order signal (1 of FIGS. 2 and FIGS. 3) st The order) may refer to an effective signal. For example, the effective signal may be near-infrared, and signal noises that are not removed through resonance may be light with a wavelength shorter than near-infrared (e.g., visible light or ultraviolet light). That is, the light absorption layers (130) may absorb light with a wavelength shorter than near-infrared (e.g., visible light or ultraviolet light).

[0028] The upper and lower light absorption layers (130H, 130L) can be placed at the point where signal noise is maximum. For example, both the upper and lower light absorption layers (130H, 130L) are tertiary signals (3 in FIG. 2 and FIG. 3). rdIt may be placed at the point where the order) is maximum, but is not limited thereto. As another example, the upper light absorption layer (130H) is a third-order signal (the third in FIG. 2 and FIG. 3). rd It can be placed at the point where the order) is maximum, and the lower light absorption layer (130L) is a 5th order signal (5 in FIG. 2 and FIG. 3). th It can be placed at the point where the order is maximum, but is not limited thereto.

[0029] A near-infrared band transmission filter (100) according to embodiments of the present invention can remove signal noise that is not removed by resonance by additionally placing light absorption layers (130) at a point where the signal noise that is not removed by resonance is maximum within a cavity layer (120) that fills between mutually opposing metal reflection layers (110). By doing so, the out-of-band blocking characteristics of the near-infrared band transmission filter (100) according to embodiments of the present invention can be further improved.

[0030] FIG. 2 is experimental data to explain the transmission wavelength of a near-infrared band transmission filter according to one comparative example. FIG. 3 is experimental data to explain the transmission wavelength of a near-infrared band transmission filter according to one embodiment of the present invention.

[0031] One comparative example of FIG. 2 is an experimental example in which TiO2 is used as the cavity layer (120) and does not include light absorption layers (130). One embodiment of FIG. 3 is an experimental example in which TiO2 is used as the cavity layer (120) and includes silicon-based light absorption layers (130). One embodiment of FIG. 3 may correspond to the embodiment of FIG. 1.

[0032] Referring to FIG. 2, a near-infrared band transmission filter according to one comparative example can transmit all light of the resonating wavelength. A near-infrared band transmission filter according to one comparative example can transmit an effective signal and signal noise that is not removed through resonance. For example, a near-infrared band transmission filter according to one comparative example has a first-order signal (1st order), third signal (3 rd order), and 5th signal (5 th It can transmit a third-order signal (3 rd order) and 5th signal (5 th The transmittance of the order) is the first-order signal (1 st It can be equal to or higher than the transmittance of the order. In the case of signal noise, transmittance may decrease as the signal order increases.

[0033] Referring to FIG. 3, a near-infrared band transmission filter (100 in FIG. 1) according to one embodiment of the present invention can transmit an effective signal among light of a resonating wavelength. Signal noises that are not removed through resonance (e.g., 3 rd order and 5 th The order, etc.) can be absorbed by the light absorption layers (130 in FIG. 1), and accordingly, signal noise (e.g., 3 rd order and 5 th The transmittance of the order, etc.) can be lowered compared to the near-infrared band transmission filter according to one comparative example. For example, a first-order signal (1 st The transmittance of the third-order signal (3 rd order) and 5th signal (5 th It can be about 6 times larger than the transmittance of the order.

[0034] That is, the near-infrared band transmission filter (100 in FIG. 1) according to one embodiment of the present invention has signal noises (e.g., 3) compared to the near-infrared band transmission filter according to one comparative example. rd order and 5 th The transmittance of (order, etc.) can be reduced by more than about 6 times. Thus, it can be confirmed that the near-infrared band transmission filter (100 of FIG. 1) according to one embodiment of the present invention has improved out-of-band blocking characteristics compared to the near-infrared band transmission filter according to one comparative example.

[0035] FIG. 4 is experimental data for explaining the transmittance of a near-infrared band transmission filter (100) according to one embodiment of the present invention according to the light angle. More specifically, FIG. 4 is experimental data for explaining the change in transmittance of a near-infrared band transmission filter (100) according to one embodiment of the present invention according to the light angle (AG in FIG. 1).

[0036] Referring again to FIG. 1, light (200) can be irradiated toward a near-infrared band transmission filter (100) according to the present invention. A portion of the light (200) can pass through a metal reflective layer (110) and can be reflected by the metal reflective layer (110). The light (200) can be reflected by the metal reflective layers (110) and resonate within the cavity layer (120). Signal noise not removed through resonance can be absorbed by the light absorption layers (130).

[0037] The light (200) may have a constant light angle (AG) with respect to the metal reflective layer (110). In other words, the light (200) may be irradiated onto the metal reflective layer (110) with a constant light angle (AG). The light angle (AG) may refer to the angle between the upper surface of the metal reflective layer (110) and the path where the light (200) is incident. In other words, the sum of the light angle (AG) and the angle of incidence may be 90 degrees. For example, the light angle (AG) may be between 30 degrees and 90 degrees, but is not limited thereto.

[0038] Referring to FIGS. 1 and 4, when the angle of view (AG) is 60 degrees (i.e., when the angle of incidence is 30 degrees), the transmittance may increase compared to when the angle of view (AG) is 90 degrees (i.e., when the angle of incidence is 0 degrees), but the wavelength of the light (200) may be shifted. For the same light (200), when the angle of view (AG) is 60 degrees (i.e., when the angle of incidence is 30 degrees), light of a wavelength smaller by a change amount (SH) may resonate compared to when the angle of view (AG) is 90 degrees (i.e., when the angle of incidence is 0 degrees). For example, the change amount (SH) may be less than about 10 nm, but is not limited thereto.

[0039] FIG. 5 is experimental data for explaining the relative strength of a first-order signal of a near-infrared band transmission filter according to one embodiment of the present invention. FIG. 6 is experimental data for explaining the relative strength of a third-order signal of a near-infrared band transmission filter according to one embodiment of the present invention. FIG. 7 is experimental data for explaining the relative strength of a fifth-order signal of a near-infrared band transmission filter according to one embodiment of the present invention.

[0040] More specifically, FIG. 5 is experimental data showing the electromagnetic field distribution of a first-order signal having a wavelength of about 924 nm, FIG. 6 is experimental data showing the electromagnetic field distribution of a third-order signal having a wavelength of about 494 nm, and FIG. 7 is experimental data showing the electromagnetic field distribution of a fifth-order signal having a wavelength of about 375 nm.

[0041] Referring to FIGS. 5, 6, and 7, it can be seen that a first signal having a wavelength of about 924 nm has a maximum intensity in the first region (MA1), a second signal having a wavelength of about 494 nm has a maximum intensity in the second region (MA2), and a third signal having a wavelength of about 375 nm has a maximum intensity in the third region (MA3).

[0042] By placing light absorption layers (130 in FIG. 1) in the second and third regions (MA2, MA3) where the intensity of the third and fifth signals is maximum, the absorption rate of signal noise can be improved and the transmittance of signal noise can be reduced, and at the same time, by not placing light absorption layers (130 in FIG. 1) in the first region (MA1) where the intensity of the first signal is maximum, the transmittance of the effective signal can be improved. Thus, the near-infrared band transmission filter (100 in FIG. 1) according to the embodiments of the present invention can further improve the effective signal transmission characteristics and out-of-band blocking characteristics.

[0043] FIG. 8 is a cross-sectional view showing a near-infrared band transmission filter according to another embodiment of the present invention. However, the explanation focuses on the differences from the semiconductor device according to the embodiments of the present invention described above. For the sake of brevity, specific descriptions of configurations identical or similar to those described above may be omitted.

[0044] Referring to FIG. 8, external cavity layers (120') may be additionally disposed on the exposed upper or lower surface of each of the metal reflective layers (110). Each of the external cavity layers (120') may be disposed spaced apart from each other in a first direction (D1) and may be in contact with adjacent metal reflective layers (110).

[0045] For example, the height of each of the outer cavity layers (120') in the first direction (D1) may be 100 nm.

[0046] The outer cavity layers (120') may include a dielectric material. For example, the cavity layer (120) may include at least one of silicon oxide, titanium oxide, yttrium fluoride, tantalum oxide, zinc oxide, zinc sulfide, or a combination thereof.

[0047] FIG. 9 is experimental data to explain the transmission wavelength of a near-infrared band transmission filter according to another comparative example. FIG. 10 is experimental data to explain the transmission wavelength of a near-infrared band transmission filter according to another embodiment of the present invention.

[0048] Another comparative example of FIG. 9 is an experimental example in which TiO2 is used as the cavity layer (120) and outer cavity layers (120') and does not include light absorption layers (130). Another embodiment of FIG. 10 is an experimental example in which TiO2 is used as the cavity layer (120) and outer cavity layers (120') and includes silicon-based light absorption layers (130). Another embodiment of FIG. 10 may correspond to the embodiment of FIG. 8.

[0049] Referring to FIG. 9, a near-infrared band transmission filter according to another comparative example can transmit all light of the resonating wavelength. A near-infrared band transmission filter according to another comparative example can transmit effective signals and signal noise that is not removed through resonance. For example, a near-infrared band transmission filter according to another comparative example has a first-order signal (1 st order), third signal (3 rd order), 5th signal (5 th order), and 7th signal (7 th It can transmit a third-order signal (3 rd The transmittance of the order) is the first-order signal (1 st It can be equal to or higher than the transmittance of the order, and the 5th order signal (5 th order) and 7th signal (7 th The transmittance of the order) is the first-order signal (1 st It may be lower than the transmittance of the order. In the case of signal noise, transmittance may decrease as the signal order increases.

[0050] Referring to FIG. 10, a near-infrared band transmission filter (100 in FIG. 8) according to another embodiment of the present invention can transmit an effective signal among light of a resonating wavelength. Signal noises that are not removed through resonance (e.g., 3 rd order, 5 th order, and 7 th The order, etc.) can be absorbed by the light absorption layers (130 in FIG. 8), and accordingly, signal noise (e.g., 3 rd order, 5 th order, and 7 th The transmittance of the order, etc., can be lowered compared to the near-infrared band transmission filter (100 in FIG. 8) according to other comparative examples. For example, a first signal (1 st The transmittance of the third-order signal (3 rd order), 5th signal (5 th order), and 7th signal (7 th It can be about 8 times larger than the transmittance of the order.

[0051] That is, the near-infrared band transmission filter (100 in FIG. 8) according to another embodiment of the present invention has signal noises (e.g., 3) compared to the near-infrared band transmission filter according to another comparative example. rd order, 5 th order, and 7 th The transmittance of (order, etc.) can be reduced by more than 8 times. Thus, it can be confirmed that the near-infrared band transmission filter (100 in FIG. 8) according to another embodiment of the present invention has improved out-of-band blocking characteristics compared to the near-infrared band transmission filter according to another comparative example.

[0052] Although embodiments of the present invention have been described above with reference to the attached drawings, the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A near-infrared band transmission filter comprising: metal reflective layers spaced apart from each other in a first direction; a cavity layer interposed between the metal reflective layers; and light absorption layers spaced apart from each other in the first direction within the cavity layer, wherein each of the light absorption layers is spaced apart from the metal reflective layers in the first direction, and the light absorption layers absorb visible light or ultraviolet light. Claim 2 delete Claim 3 A near-infrared band transmission filter according to claim 1, wherein the height of each of the light absorption layers in the first direction is 5 nm or more and 50 nm or less. Claim 4 A near-infrared band transmission filter according to claim 1, wherein the distance between adjacent light absorption layers is longer than the distance between the light absorption layers and the adjacent metal reflection layers. Claim 5 A near-infrared band transmission filter according to claim 1, wherein the light absorption layers include a lower light absorption layer and an upper light absorption layer spaced apart from the lower light absorption layer in the first direction, and wherein the lower light absorption layer and the upper light absorption layer comprise different materials. Claim 6 In claim 1, each of the metal reflective layers comprises at least one of Ag, Au, Al, Cu, Ti, or a combination thereof, a near-infrared band transmission filter. Claim 7 In claim 1, the cavity layer comprises at least one of silicon oxide, titanium oxide, yttrium fluoride, tantalum oxide, zinc oxide, zinc sulfide, or a combination thereof, for a near-infrared band transmission filter. Claim 8 In claim 1, the light absorption layers comprise at least one of silicon, germanium, perovskite, cadmium telluride, a visible light absorbing dye, or a combination thereof, forming a near-infrared band transmission filter. Claim 9 A near-infrared band transmission filter according to claim 1, further comprising outer cavity layers covering the metal reflective layers.

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