Non-metal medium transmission grating narrow-band filter based on guided-mode resonance principle

Abstract

The application discloses a non-metal medium transmission grating narrow-band filter based on a guided-mode resonance principle, which comprises a substrate, a first medium layer, a second medium layer, a third medium layer, a fourth medium layer, a fifth medium layer, a medium grating, a sixth medium layer, a seventh medium and an eighth medium layer. The refractive indexes of the first medium layer, the fourth medium layer and the sixth medium layer are higher than that of the second medium layer; the refractive index of the second medium layer is greater than those of the third medium layer, the fifth medium layer and the seventh medium layer. In the application, the first medium layer, the third medium layer, the fourth medium layer, the fifth medium layer, the sixth medium layer and the seventh medium layer construct a transmission band-stop filter in a visible light wave band, form a sideband suppression layer and can effectively suppress sidebands and improve the color purity of filtered light.

Description

Technical Field

[0001] This invention relates to the field of optical filter technology, specifically to a non-metallic dielectric transmission grating narrowband optical filter based on the guided mode resonance principle. Background Technology

[0002] Traditional visible light filters are mainly made of organic dye molecules. However, the dye molecules in organic dye filters are prone to degradation and aging under high temperatures and ultraviolet light, resulting in limitations in performance, scalability, and durability. With the development of nanofabrication technology, guided-mode resonance has been widely utilized, becoming one of the important ways to solve the above problems.

[0003] Guided-mode resonant filter structures outperform dye-based filters in terms of dimensional tunability, integration, and stability. Guided-mode resonant filters are a novel and unique type of optical filter that can generate extremely narrow bandwidth reflection or transmission peaks over a wide wavelength range. The main methods for implementing guided-mode resonant filters include: metal grating guided-mode resonance and non-metallic dielectric guided-mode resonance.

[0004] However, parameters such as the period, groove depth, and waveguide layer thickness of metal grating guided mode resonant filters have a significant impact on them. Furthermore, due to the inherent ohmic loss and material dispersion of metals, peak transmittance is low and bandwidth is large, affecting practical applications. Although using dielectric materials can avoid the losses caused by metals, most existing non-metallic dielectric guided mode resonant filters are reflective, with few used in transmission applications, which severely limits the application areas of non-metallic dielectric guided mode resonants. Summary of the Invention

[0005] This invention addresses the ohmic damage and material dispersion problems of current subwavelength metal grating guided mode resonant filters, as well as the lack of transmission capability in non-metallic dielectric grating guided mode resonant filters. It proposes a non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle includes a substrate, a first dielectric layer, a second dielectric layer, a third dielectric layer, a fourth dielectric layer, a fifth dielectric layer, a dielectric grating, a sixth dielectric layer, a seventh dielectric layer, and an eighth dielectric layer. The refractive indices of the first, fourth, and sixth dielectric layers are higher than those of the second dielectric layer; the refractive index of the second dielectric layer is greater than that of the third, fifth, and seventh dielectric layers.

[0007] Preferably, the dielectric grating is made of silicon, has a thickness of 135 nm, has equal-height parallel symmetrical grating ridges, a gap width of 20 nm-40 nm, and a duty cycle of 0.75-0.85. Preferably, the substrate is made of quartz with a refractive index of 1.52.

[0008] Preferably, the first, fourth, and sixth dielectric layers are made of silicon; the third, fifth, and seventh dielectric layers are made of potassium fluoride; and the second dielectric layer is made of silicon nitride.

[0009] Preferably, the air layer between the sixth dielectric layer and the dielectric grating has a refractive index of 1 and a thickness between 80 nm and 120 nm.

[0010] Preferably, the first dielectric layer, the third dielectric layer, the fourth dielectric layer, the fifth dielectric layer, the sixth dielectric layer, and the seventh dielectric layer constitute a transmissive bandstop filter in the visible light band.

[0011] Preferably, the second dielectric layer is a matching layer, and its refractive index is between that of high and low refractive index materials constituting a transmissive bandstop filter in the visible light band, so as to satisfy the matching between the incident layer and the exit layer.

[0012] Using the above technical solution, the first, third, fourth, fifth, sixth and seventh dielectric layers construct a transmissive bandstop filter in the visible light band, forming a sideband suppression layer that can effectively suppress sidebands and improve the color purity of the filtered light.

[0013] The principle of subwavelength nonmetallic dielectric guided mode resonance avoids the inherent losses of metal gratings, thus improving the utilization efficiency of incident light. Furthermore, by adjusting the grating period, the center wavelength can be moved within the visible light range, enabling selection of continuous wavelengths within that range.

[0014] The second dielectric layer is a matching layer, which can improve transmittance and reduce the full width at half maximum (FWHM) to a certain extent. Its refractive index should be between that of high and low refractive index materials used in constructing transmissive bandstop filters in the visible light band. Compared with filters of other subwavelength gratings, the filter of the present invention has outstanding advantages such as low sideband, narrow FWHM, high transmittance, and continuous adjustability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic front view of a non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle of the present invention.

[0017] Figure 2 This is a top-view schematic diagram of the grating portion of a non-metallic dielectric transmission grating narrowband filter structure based on the guided mode resonance principle of the present invention.

[0018] Figure 3 This is a schematic diagram illustrating the working principle of the present invention.

[0019] Figure 4 This is a simulation diagram of the transmission spectrum at different wavelengths by adjusting parameters according to the present invention. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] This invention provides a non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle, such as... Figure 1 As shown, the structure includes a substrate 1, a first dielectric layer 2, a second dielectric layer 3, a third dielectric layer 4, a fourth dielectric layer 5, a fifth dielectric layer 6, a dielectric grating 7, a sixth dielectric layer 8, and a seventh dielectric layer 9. The refractive indices of the first, fourth, and sixth dielectric layers are higher than those of the second dielectric layer; the refractive index of the second dielectric layer is greater than that of the third, fifth, and seventh dielectric layers.

[0024] The substrate 1 is made of quartz with a refractive index of 1.52.

[0025] Among them, the first dielectric layer 2, the fourth dielectric layer 5 and the sixth dielectric layer 8 are made of the same material and are high refractive index materials; the third dielectric layer 4, the fifth dielectric layer 6 and the seventh dielectric layer 9 are made of the same material and are low refractive index materials.

[0026] Furthermore, the space between the sixth dielectric layer 8 and the dielectric grating 7 is filled with an air layer, the refractive index of which is 1 and the thickness is between 80nm and 120nm.

[0027] As is understandable, the air layer is formed by a support and a sacrificial layer, which is a conventional technique and therefore is not shown in the figure.

[0028] Specifically, in this embodiment, the dielectric grating is a parallel symmetrical grating strip with two symmetrical grating ridges within a single period. It is made of silicon, with a thickness of 135 nm and a duty cycle of 0.75~0.85. The first, fourth, and sixth dielectric layers are made of silicon with a thickness of 30 nm. The second dielectric layer is made of silicon nitride with a thickness of 85 nm-100 nm. The third, fifth, and seventh dielectric layers are made of potassium fluoride with a thickness of 120 nm. The refractive index between the grating layer and the eighth dielectric layer is 1, and the thickness is between 80 nm and 120 nm. The first, third, fourth, fifth, sixth, and seventh dielectric layers constitute a transmissive bandstop filter in the visible light band of this filter, significantly reducing the sidebands of the transmissive filter. The third dielectric layer is a matching layer, effectively matching the refractive index between the top layer of the grating and the substrate, reducing sidebands and improving transmittance. Based on the characteristics of subwavelength gratings, the center wavelength can be moved within the visible light range by adjusting the grating period, thus achieving tunability of continuous wavelengths within the visible light range.

[0029] It should be noted that refractive index is divided into three categories: low, medium, and high. Below 1.50 is called low refractive index, 1.56 is generally called medium refractive index, and above 1.6 is called high refractive index.

[0030] like Figure 3As shown, the working principle of a non-metallic dielectric transmission grating narrowband filter based on the guided-mode resonance principle is as follows: Incident light is perpendicularly incident, passes through the substrate, and enters a low-pass filter composed of high and low refractive indices from a first, third, fourth, fifth, sixth, and seventh dielectric layer. The light then reaches the non-metallic dielectric grating strip, where subwavelength diffraction occurs. The zero-order diffraction resonates with the guided modes of the periodic modulation waveguide formed by the grating, thereby achieving light transmission at a specific frequency, increasing transmittance, reducing sidebands, and obtaining a narrow full width at half maximum (FWHM) of the transmission spectrum. Since the coupling between the non-metallic dielectric grating and the low-pass filter is affected by the incident and exiting media, the second dielectric layer serves as a matching layer to match the refractive index changes between the substrate and the top layer film system.

[0031] like Figure 4 As shown, in the visible light band, the period and duty cycle of the dielectric grating 7 can be adjusted to meet the matching conditions with the incident light wave vector, thereby enabling the selection of different wavelengths.

[0032] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments, including components, without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle, characterized in that, The structure includes, from bottom to top, a substrate (1), a first dielectric layer (2), a second dielectric layer (3), a third dielectric layer (4), a fourth dielectric layer (5), a fifth dielectric layer (6), a dielectric grating (7), a sixth dielectric layer (8), and a seventh dielectric layer (9). The first dielectric layer (2), the fourth dielectric layer (5), and the sixth dielectric layer (8) are made of the same high-refractive-index material; the third dielectric layer (4), the fifth dielectric layer (6), and the seventh dielectric layer (9) are made of the same low-refractive-index material; and the second dielectric layer (3) is located between the first dielectric layer (2) and the third dielectric layer (4). The material is a low refractive index material; the space between the sixth dielectric layer (8) and the dielectric grating (7) is filled with an air layer, the material of the dielectric grating (7) is silicon, the dielectric grating (7) is composed of two symmetrical grating ridges, the materials of the first dielectric layer (2), the fourth dielectric layer (5) and the sixth dielectric layer (8) are silicon, the materials of the third dielectric layer (4), the fifth dielectric layer (6) and the seventh dielectric layer (9) are potassium fluoride, and the first dielectric layer, the third dielectric layer, the fourth dielectric layer, the fifth dielectric layer, the sixth dielectric layer and the seventh dielectric layer constitute a transmission bandstop filter in the visible light band.

2. The non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle according to claim 1, characterized in that, The thickness of the dielectric grating (7) is 125nm~140nm, and the duty cycle is 0.75~0.

85.

3. The non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle according to claim 1, characterized in that, The substrate (1) is made of quartz with a refractive index of 1.

52.

4. The non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle according to claim 1, characterized in that, The second dielectric layer (3) is a matching layer, and its material is silicon nitride.

5. The non-metallic dielectric transmission grating narrowband filter based on the guided mode resonance principle according to claim 1, characterized in that, The refractive index of the air layer between the sixth dielectric layer (8) and the dielectric grating (7) is 1, and the thickness of the air layer is between 80nm and 120nm.

Images