Light splitting device and preparation method thereof

Abstract

The invention provides a light splitting device and a preparation method thereof, and relates to the technical field of optical elements. The light splitting device comprises an optical filter used for filtering incident light into light with at least one specific wavelength; the optical grating is arranged on one side of the optical filter and is used for filtering incident light into light in a specific polarization direction; wherein the grating comprises a plurality of grid bars distributed in a linear array and a first metal layer located among the plurality of grid bars, and each grid bar comprises a dielectric layer and a second metal layer covering the surface, away from the optical filter, of the dielectric layer. According to the invention, the optical filter and the grating are integrated to realize simultaneous light splitting of spectrum and polarization. Meanwhile, the multi-layer structure of the grating can further improve the polarization beam splitting effect. In addition, a spectrum light splitting device and a polarization light splitting device are integrated, so that the problems of large size and poor stability of a light splitting device in the prior art are solved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical elements, and in particular to a spectroscopic device and a method for preparing the same. Background Art

[0002] Spectral spectroscopy technology has a wide range of applications in military and civilian fields such as environmental monitoring, agricultural science and technology, and detection of targets such as missiles, meteors, clouds, rain, landforms and their backgrounds in the ground, aviation and aerospace fields. At the same time, polarization spectroscopy technology plays a vital role in ground and space remote sensing, mineral exploration, underwater target detection and identification. With the continuous development of emerging fields such as communications, meteorological detection, and military reconnaissance, traditional, single-attribute optical detection methods can no longer meet actual application needs. Therefore, there is an urgent need for a high-precision detection system that can simultaneously obtain spectral information and polarization information. More specifically, a spectrometer that can simultaneously achieve spectral spectroscopy and polarization spectroscopy is needed.

[0003] In the related art, a discrete system combining a spectral spectrometer and a polarizer can be used to obtain polarized monochromatic light. However, the discrete system has the problems of large size, difficult integration and poor stability. Therefore, there is an urgent need to find a spectral and polarization simultaneous spectrometer with small size, simple structure, good stability and easy integration. Summary of the invention

[0004] In view of this, the present disclosure provides a spectroscopic device and a method for preparing the same, so as to solve the problems in the related art that the discrete system of the combination of the spectral spectroscopic device and the polarizer is large in size, difficult to integrate and has poor stability.

[0005] In a first aspect, a spectroscopic device is provided, comprising: a filter for filtering first incident light into light of at least one specific wavelength; and a grating arranged on one side of the filter, for filtering second incident light into light of a specific polarization direction; wherein the grating comprises a plurality of bars distributed in a linear array, and a first metal layer located between the plurality of bars, and the bars comprise a dielectric layer, and a second metal layer covering a surface of the dielectric layer away from the filter.

[0006] In some embodiments, the filter includes: a first reflective layer, an intermediate layer and a second reflective layer, the intermediate layer includes a first surface and a second surface arranged in parallel, the first reflective layer is stacked on the first surface, and the second reflective layer is stacked on the second surface.

[0007] In some embodiments, the first reflective layer includes a plurality of overlapping first refractive index film layers and a second refractive index film layer, and the second reflective layer includes a plurality of overlapping first refractive index film layers and a second refractive index film layer; wherein the refractive index of the first refractive index film layer is greater than the refractive index of the second refractive index film layer.

[0008] In some embodiments, the optical thicknesses of the first refractive index film layer and the second refractive index film layer are equal and are one quarter of the applied wavelength of the filter; the optical thickness of the intermediate layer is an integer multiple of one half of the applied wavelength.

[0009] In some embodiments, the middle layer includes a plurality of stepped portions arranged in parallel, and the thicknesses of the plurality of stepped portions are not completely the same, so as to form a plurality of spectral splitting channels.

[0010] In some embodiments, the thickness of the dielectric layer is greater than the thickness of the first metal layer, and the difference between the thickness of the dielectric layer and the thickness of the first metal layer is 4n times the application wavelength of the filter. TE An odd multiple of one, where n TE is the equivalent refractive index of TE polarized light.

[0011] In some embodiments, the ratio of the width of the grating stripes to the grating period of the grating stripes is 1:10 to 9:10.

[0012] In a second aspect, a method for preparing a spectroscopic device is provided, comprising: coating a filter on a substrate; coating a layer to be etched and a grating mask pattern on the surface of the filter in sequence, and etching the layer to be etched based on the grating mask pattern to form a dielectric layer of a grating bar; coating metal between the dielectric layers of the grating bars and on the surface of the dielectric layer away from the filter to form a first metal layer and a second metal layer of the grating bars.

[0013] In some embodiments, before plating metal between the dielectric layers of the grid bars and on the surface of the dielectric layer away from the filter, the method also includes: plating an adhesion metal layer between the dielectric layers of the grid bars and on the surface of the dielectric layer away from the filter, and the material of the adhesion metal layer includes: Ti or Cr.

[0014] The spectrometer provided by the embodiment of the present disclosure sets the grating on one side of the filter, uses the grating characteristics to split the polarization of the incident light, and uses the filter characteristics to split the spectrum of the incident light, thereby achieving simultaneous spectral and polarization splitting. At the same time, the multi-layer structure of the grating can further suppress the polarized light parallel to the grating direction, thereby improving the polarization splitting effect. In addition, the spectrometer provided by the embodiment of the present disclosure integrates the spectral spectrometer and the polarization spectrometer into one, thereby solving the problem of large size and poor stability of the spectrometer in the related art. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Shown is a schematic structural diagram of a spectrometer provided in an embodiment of the present disclosure.

[0016] Figure 2 Shown is a schematic structural diagram of a filter provided in an embodiment of the present disclosure.

[0017] Figure 3Shown is a schematic structural diagram of a first reflective layer and / or a second reflective layer provided in an embodiment of the present disclosure.

[0018] Figure 4 Shown is a schematic structural diagram of a filter including a plurality of stepped portions provided in an embodiment of the present disclosure.

[0019] Figure 5 The figure shows a schematic diagram of polarized light transmission spectra and polarization extinction ratio curves in TE and TM polarization modes when incident light enters a spectrometer provided by an embodiment of the present disclosure.

[0020] Figure 6 The figure shows a schematic diagram of polarized light transmission spectra and polarization extinction ratio curves in TE and TM polarization modes when incident light enters another spectrometer provided by an embodiment of the present disclosure.

[0021] Figure 7 The figure shows a schematic diagram of polarized light transmission spectra and polarization extinction ratio curves in TE and TM polarization modes when incident light enters another spectrometer provided by an embodiment of the present disclosure.

[0022] Figure 8 The figure is a schematic flow chart of a method for preparing a spectrometer provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0024] In the related art, if you want to directly obtain polarized monochromatic light, you can only use a discrete system that combines a spectrometer and a polarizer, except for laser. However, the discrete system is large and difficult to integrate, and the interaction between the spectrometer and the polarizer easily leads to poor system stability. Therefore, the present invention integrates the optical microcavity and the grating structure to provide a spectral and polarization simultaneous spectrometer that is small in size, simple in structure, good in stability, and easy to integrate.

[0025] Figure 1 FIG. 1 is a schematic diagram of the structure of a light splitting device provided by an embodiment of the present disclosure. Figure 1As shown, the spectroscopic device includes a filter 1 and a grating 2. The filter 1 is capable of filtering the light incident on the filter 1 (i.e., the first incident light) into light of at least one specific wavelength. Exemplarily, the filter 1 is a Fabry-Perot (FP) filter. The grating 2 is arranged on one side of the filter 1, and is composed of a plurality of gratings 21 distributed in a linear array and a first metal layer 22. Each grating 21 includes a dielectric layer 211, and a second metal layer 212 covering the surface of the dielectric layer 211 away from the filter 1. The first metal layer 22 is located between the plurality of gratings 21, and covers a portion of the surface of the filter 1 on the side where the grating 2 is arranged, where the grating 2 is not arranged. At this time, the dielectric layer 211, the second metal layer 212, and the first metal layer 22 of the multiple gratings 21 work together to absorb and suppress the linear polarized light TE in the incident light whose electric field is parallel to the grating direction, so as to filter the light incident on the grating 2 (i.e., the second incident light) into light with a specific polarization direction, i.e., the linear polarized light TM in the grating direction whose electric field is perpendicular to the grating direction. At the same time, the multi-layer structure of the grating works together to form a type of resonant cavity structure, so that the incident light can form a standing wave resonance in the resonant cavity structure, further suppressing the TE polarized light.

[0026] Among them, the first incident light and the second incident light are intended to distinguish the light incident on the filter 1 and the grating 2, and do not indicate the order of their incidence. Exemplarily, the incident light is incident on the spectroscopic device from the surface of the grating 2 away from the filter 1. At this time, the incident light is the second incident light; the second incident light is absorbed and suppressed by the grating 2 on the TE polarized light, and polarized light with the TM polarization mode as the main mode is obtained. Furthermore, the polarized light continues to be incident on the filter 1 from the surface on the side where the filter 1 contacts the grating 2. At this time, the polarized light is the first incident light; the first incident light is subjected to the spectral splitting effect of the filter 1, and finally obtains light with a specific polarization direction and a specific wavelength.

[0027] In some embodiments, the filter 1 includes a first reflective layer, an intermediate layer and a second reflective layer.

[0028] Figure 2 FIG. 1 is a schematic diagram of the structure of a filter provided by an embodiment of the present disclosure. Figure 2 As shown, the filter 1 is composed of a first reflective layer 11, an intermediate layer 12 and a second reflective layer 13. The intermediate layer 12 includes a first surface and a second surface arranged in parallel, the first reflective layer 11 is stacked on the first surface, and the second reflective layer 13 is stacked on the second surface. The first reflective layer 11, the intermediate layer 12 and the second reflective layer 13 together form a resonant cavity, which can be used to control the characteristics of the oscillating light beam in the cavity, including the wavelength, to achieve a spectral splitting function and filter the incident light into at least one specific wavelength of light.

[0029] In some embodiments, the optical filter 1 is a full dielectric filter, that is, the materials of the first reflective layer 11 , the middle layer 12 , and the second reflective layer 13 of the optical filter 1 are all dielectric. Figure 3 FIG. 1 is a schematic diagram of the structure of a first reflective layer and / or a second reflective layer provided in an embodiment of the present disclosure. Figure 3 As shown, the first reflective layer 11 includes a plurality of first refractive index film layers and a second refractive index film layers that are overlapped, and the second reflective layer 13 includes a plurality of first refractive index film layers and a second refractive index film layers that are overlapped; wherein the refractive index of the first refractive index film layer is greater than the refractive index of the second refractive index film layer. The intermediate layer 12 may be made of the same medium as the first refractive index film layer or the second refractive index film layer, or may be made of a medium different from the first refractive index film layer and the second refractive index film layer.

[0030] Exemplarily, the film system expression of filter 1 is (LH) m xL(HL) m-1 H or L (HL) m xH(LH) m , where H represents the first refractive index film layer; L represents the second refractive index film layer; m is the number of times the high refractive index film layer and the low refractive index film layer are alternately stacked, m>2 and the larger the m, the narrower the filter spectral bandwidth; xL or xH is the intermediate layer 12, with the first reflective layer 11 and the second reflective layer 13 on both sides, and x is the multiple of the first / second refractive index film layer (H / L). The material of the first refractive index film layer can be a high refractive index dielectric material that is transparent at the application wavelength, including but not limited to Ge, TiO2, Nb2O5, HfO2, Ta2O5 or Si; the material of the first refractive index film layer can be a low refractive index dielectric material that is transparent at the application wavelength, including but not limited to SiO2, ZnS, SiO, HfO2 or Al2O3.

[0031] The manufacturing process of all-dielectric filters is relatively simple, with high transmittance and reflectivity, stable optical performance, and not easily affected by environmental factors such as temperature and humidity. It can effectively filter incident light of multiple wavelengths and has a wide range of applications.

[0032] The first reflective layer 11, the middle layer 12 and the second reflective layer 13 of the filter 1 together form a resonant cavity. The spacing between the first reflective layer 11 and the second reflective layer 13 determines the wavelength restriction of the resonant cavity. Therefore, the application wavelength of the filter 1, that is, the specific wavelength finally filtered by the filter, can be changed by adjusting the spacing.

[0033] Therefore, the application wavelength of the filter can be changed by adjusting the thickness of the intermediate layer. In some embodiments, the intermediate layer 12 includes a plurality of stepped portions arranged in parallel, each of which has the same thickness, but the thicknesses of the plurality of stepped portions are not completely the same. The plurality of stepped portions can be arranged in sequence according to their respective thicknesses, or can be arranged in a random order according to actual application requirements. Figure 4 FIG. 1 is a schematic diagram of the structure of a filter including multiple stepped portions provided by an embodiment of the present disclosure. Figure 4 As shown, the thickness of each of the multiple step portions of the intermediate layer 12 is different, and they are arranged in parallel in descending order of thickness. The upper surface and the lower surface of each step portion are provided with a first reflection layer and a second reflection layer, and each step portion and the two reflection layers can form a resonant cavity, and each resonant cavity with different thicknesses can filter a specific wavelength of light. Therefore, the filter can realize multi-spectral spectrometry by providing step portions with different thicknesses, that is, a filter with different passband peaks is formed, so that the spectrometer provided in the embodiment of the present disclosure can meet the needs of multi-spectral spectrometry.

[0034] In some embodiments, the optical thickness of the first refractive index film layer and the second refractive index film layer are equal and are one quarter of the applied wavelength of the optical filter 1. The optical thickness refers to the ratio of the actual length that the incident light passes through a certain medium to the length of the medium in a vacuum due to the change in the refractive index of the medium. At this time, the interference effect between the two reflective layers and the middle layer on the applied wavelength is the largest, and the maximum reflectivity and minimum transmittance can be achieved to achieve the best performance of the optical filter.

[0035] In some embodiments, the optical thickness of the intermediate layer 12 is N / 2 of the applied wavelength, where N is a positive integer. At this time, only the light of the applied wavelength will form a standing wave resonance in the resonant cavity, so that the light of the applied wavelength is selectively transmitted to achieve the best performance of the filter.

[0036] The structure of the filter in the spectrometer provided by the embodiment of the present disclosure is described in detail above. The grating in the spectrometer provided by the embodiment of the present disclosure will be described in detail below in conjunction with the drawings in the embodiment of the present disclosure.

[0037] Continue to refer Figure 1 The first metal layer 22 can be composed of a metal with a certain reflectivity and conductivity, including but not limited to Au, Ag, Al, Cu or their alloys; the dielectric layer 211 can be composed of a low-refractive index material that is transparent in the application band, including but not limited to SiO2, ZnS, SiO, HfO2 or Al2O3; the second metal layer 212 can be composed of a metal with a certain reflectivity and conductivity, including but not limited to Au, Ag, Al, Cu or their alloys, wherein the material of the first metal layer 212 and the second metal layer 212 may be the same or different.

[0038] The grating period of the grating is p, and the grating period is the length from one refractive index change point to an adjacent refractive index change point; the width of the grating bar 21 is w and the thickness is h2+h3, wherein h2 is the thickness of the dielectric layer 211 and h3 is the thickness of the second metal layer 212; the width of the first metal layer 22 between the two grating bars 21 is pw and the thickness is h1, wherein the thickness h1 of the first metal layer 22 and the thickness h3 of the second metal layer 212 may be the same or different.

[0039] In some embodiments, a plurality of grating bars are arranged in parallel and equidistantly, and the grating period of the grating bars is smaller than the application wavelength of the filter. The grating bars will diffract the incident light, and at this time, the grating period determines the angle and intensity of the diffraction. The grating period is smaller than the application wavelength of the filter, which can ensure that the incident light is correctly diffracted, and within a certain range, the smaller the grating period, the higher the polarization selectivity of the grating for linearly polarized light (that is, the ratio of the TM transmittance of linearly polarized light with the electric field perpendicular to the grating bar direction to the TE transmittance of linearly polarized light with the electric field parallel to the grating bar direction). Exemplarily, the grating period of the grating bars is less than one-fifth of the application wavelength of the filter to obtain a higher extinction ratio of linearly polarized light, increase the proportion of TM polarized light in the light passing through the grating, and enhance the polarization splitting effect of the grating. Further, the polarization splitting effect of the splitting device is enhanced.

[0040] In some embodiments, the width w of the grating strip 21 is smaller than the grating period p. Approaches 0, that is, the width of the grating w approaches 0 and the width of the first metal layer between the two gratings is pw approaches p. At this time, the surface of the filter as a whole approaches a layered structure covered by the first metal layer, which will cause the polarization selectivity of the grating to decrease and the polarization splitting effect to weaken. Similarly, the duty cycle f approaches 1, that is, the width of the grating w approaches p and the width of the first metal layer between the two gratings is pw approaches 0. At this time, the surface of the filter as a whole approaches a layered structure covered by the grating, which will cause the polarization selectivity of the grating to decrease and the polarization splitting effect to weaken. Therefore, the duty cycle needs to be kept within a specific range. Exemplarily, the ratio of the width w of the grating to the grating period p is 1:10 to 9:10, that is, the duty cycle f is one tenth to nine tenths. At this time, the structure of the grating is appropriate and the polarization selectivity is relatively high to ensure the polarization splitting effect of the grating.

[0041] In some embodiments, the thickness h1 of the first metal layer 22 is not less than the skin depth of the electromagnetic wave in the metal. Electromagnetic waves can form an electric field on the metal surface, thereby exciting current. For high-frequency electromagnetic waves, the current distribution becomes uneven, and most of it will be concentrated near the surface of the conductor. It is difficult for high-frequency electromagnetic waves to penetrate the metal surface. Therefore, for high-frequency electromagnetic waves such as light, the skin depth in the metal is very small. In order to reduce the loss of light in the first metal layer 22, the thickness h1 of the first metal layer 22 should not be less than the skin depth of the electromagnetic wave in the metal. Exemplarily, the thickness h1 of the first metal layer 22 is not less than twice the skin depth of the electromagnetic wave in the metal. According to electromagnetic wave theory, it can be obtained that the skin depth of the electromagnetic wave in the metal is approximately Where λ is the wavelength of the electromagnetic wave, h1 is not less than 0.0096 times the square root of the applied wavelength in micrometers.

[0042] For the same reason, the thickness h3 of the second metal layer 212 is not less than the skin depth of the electromagnetic wave in the metal. Exemplarily, the thickness h3 of the second metal layer 212 is not less than 2 times the skin depth of the electromagnetic wave in the metal to reduce the loss of light in the second metal layer 212.

[0043] The thicker the first metal layer 22 and the second metal layer 212 are, the stronger the shielding effect of the grating on TE polarized light is, and thus the higher the polarization selectivity is, and the stronger the polarization splitting effect of the grating is. However, the thickness of the first metal layer 22 is also restricted by the thickness of the dielectric layer 211 of the grid bar 21.

[0044] In some embodiments, the thickness of the first metal layer 22 is less than the thickness of the dielectric layer. At this time, the second metal layer 212 of the grid bar 21, the dielectric layer 211 of the grid bar 21, and the first metal layer 22 together form a three-layer structure. In this structure, the first metal layer 22 and the second metal layer 212 are two mutually parallel planar reflection layers, so that the structure becomes a quasi-FP cavity (Fabry-Perot resonant cavity). Incident light of a specific wavelength can form a standing wave resonance in the quasi-Fabry-Perot resonant cavity, so that the energy is repeatedly reflected in the cavity, thereby enhancing the transmission and capture of energy. Therefore, by adjusting the thickness of the intermediate cavity layer between the first metal layer 22 and the second metal layer 212, the structure can have an enhancing or weakening effect on light of a specific wavelength, so that the grating emits a narrow-band spectrum of the TM polarization mode with high transmittance, so as to improve the polarization splitting effect of the grating.

[0045] Specifically, according to the equivalent medium theory, the grating as a whole can be regarded as an equivalent medium layer. When the equivalent optical thickness is equal to an odd multiple of one quarter of the designed application wavelength λ0, the grating as a whole can act as an anti-reflection layer. At this time, the TM polarization transmittance at the application wavelength reaches the maximum. Among them, the anti-reflection layer can use the different refractive indices between different media to form interference between the reflection and transmission of the incident light, thereby offsetting part of the reflected light and improving the transmittance and optical efficiency of the grating.

[0046] In order to obtain a high polarization extinction ratio, the thickness of the intermediate cavity layer needs to be adjusted so that the resonance mode in the FP-like cavity is different from the resonance mode of the incident light in the TE polarization mode, so as to suppress the incident light in the TE polarization mode. When the transmittance of the incident light in the TE polarization mode reaches the minimum value, the thickness of the intermediate cavity layer, that is, the difference between the thickness of the dielectric layer and the thickness of the first metal layer Among them, n TE is the equivalent refractive index of the TE polarization mode incident light on the grating, and Where n0 and n1 are the refractive indices of air and dielectric layer materials, respectively; f is the duty cycle; N is a positive integer; λ0 is the application wavelength of the filter (i.e., the application wavelength of the spectrometer). At this time, the equivalent refractive index of the incident light in the TM polarization mode is and That is, when the transmittance of incident light in TE polarization mode reaches a minimum, the grating has a higher transmittance of incident light in TM polarization mode, thereby improving the polarization extinction ratio and optical efficiency of the grating. Further, the polarization extinction ratio and optical efficiency of the spectrometer are improved.

[0047] In some embodiments, a substrate may be provided under the filter 1 to provide support. The substrate may be any optical medium material that is transparent at the application wavelength, including but not limited to fused silica glass, K9 glass, ZK6 glass, BK glass, optical glass, gemstone, zinc sulfide, zinc selenide, magnesium fluoride, silicon wafer or germanium wafer.

[0048] The structure of the spectrometer provided by the embodiment of the present disclosure is described in detail above. In the spectrometer provided by the embodiment of the present disclosure, the grating is set on one side of the filter, and the polarization of the incident light is split by the grating characteristics, and the spectrum of the incident light is split by the filter characteristics, so as to realize the simultaneous spectrum and polarization splitting; at the same time, the multi-layer structure of the grating can further suppress the polarized light parallel to the grating direction, improve the polarization splitting effect, and obtain a high-performance spectrum and polarization simultaneous splitting device. In addition, the spectrometer provided by the embodiment of the present disclosure integrates the filter and the grating into one, has a simple structure, and the shape, size, and applicable band can be freely designed. The reliability, stability, and optical efficiency of the spectrometer are improved, thereby solving the problem of large size and poor stability of the spectrometer in the related art.

[0049] For ease of understanding, the effects of the spectrometer provided by the embodiments of the present disclosure will be specifically described below in conjunction with three embodiments.

[0050] First, in some embodiments, a spectroscopic device with an application wavelength of λ0=4.27 μm is used as an example. The spectroscopic device includes a filter and a grating arranged on one side of the filter. The filter is a full dielectric FP (Fabry-Perot) filter, and the film system expression is (LH) 5 2L(HL) 4 H, where H is the first refractive index film layer Si with an optical thickness equal to λ0 / 4, and L is the second refractive index film layer SiO with an optical thickness equal to λ0 / 4. The first refractive index film layer and the second refractive index film layer are overlapped to form a first reflection layer and a second reflection layer respectively; the middle layer is composed of two layers of second refractive index film layers. The grating period of the grating is 140nm; the width of the first metal layer between the two bars is 56nm, the height is 100nm, and the material is Au; the width of the bar is 84nm, where the height of the dielectric layer of the bar is 400nm, and the material is SiO, and the height of the second metal layer of the bar is 100nm, and the material is Au.

[0051] When the incident light enters the spectrometer of this embodiment, the polarized light transmission spectra and polarization extinction ratio curves of the TE and TM polarization modes are as follows: Figure 5 As shown. The solid line represents the transmittance of TM polarized light, the dashed line represents the transmittance of TE polarized light, and the dotted line represents the polarization extinction ratio of the spectrometer (TM polarized light transmittance / TE polarized light transmittance). Figure 5 As shown, when the incident light enters the spectrometer of this embodiment, at the application wavelength of 4.27 μm of the spectrometer, the transmittance of TM polarized light is greater than 80%, the bandwidth is about 6 nm, and the polarization extinction ratio is as high as 10 6 Therefore, the spectrometer of this embodiment has good spectrum and polarization simultaneous spectrometry capabilities.

[0052] Secondly, in some other embodiments, a spectroscopic device with an application wavelength λ0=10 μm is taken as an example. The spectroscopic device includes a filter, a grating disposed on one side of the filter, and a substrate disposed on the other side of the filter. The material of the substrate is Ge. The filter is a full dielectric FP (Fabry-Perot) filter, and the film system expression is (LH) 4 2L(HL) 3H, where H is the first refractive index film layer Ge with an optical thickness equal to λ0 / 4, and L is the second refractive index film layer ZnS with an optical thickness equal to λ0 / 4. The first refractive index film layer and the second refractive index film layer are overlapped to form a first reflection layer and a second reflection layer respectively; the middle layer is composed of two layers of second refractive index film layers. The grating period of the grating is 180nm; the width of the first metal layer between the two bars is 72nm, the height is 100nm, and the material is Au; the width of the bar is 108nm, where the height of the dielectric layer of the bar is 600nm, and the material is ZnS, and the height of the second metal layer of the bar is 100nm, and the material is Au.

[0053] When the incident light enters the spectrometer of this embodiment, the polarized light transmission spectra and polarization extinction ratio curves of the TE and TM polarization modes are as follows: Figure 6 As shown. The solid line represents the transmittance of TM polarized light, the dashed line represents the transmittance of TE polarized light, and the dotted line represents the polarization extinction ratio of the spectrometer. Figure 6 As shown, when the incident light enters the spectrometer of this embodiment, at the application wavelength of 10 μm of the spectrometer, the TM polarized light transmittance is about 75%, the bandwidth is about 33 nm, and the polarization extinction ratio is as high as 4×10 5 Therefore, the spectrometer of this embodiment has good spectrum and polarization simultaneous spectrometry capabilities.

[0054] Finally, in some embodiments, taking a spectroscopic device including 8 spectral channels as an example, each spectral channel is distributed in the 3.6μm to 4.18μm band. The spectroscopic device includes a filter, a grating arranged on one side of the filter, and a substrate arranged on the other side of the filter. The material of the substrate is Si. The filter is a full dielectric FP (Fabry-Perot) filter, and the middle layer thereof includes 8 step portions arranged in parallel, and the application wavelength λ0 of each step portion is different to form 8 spectral channels. The film system expression of the filter is (LH) 5 xL(HL) 4 H, where H is the first refractive index film layer Si with an optical thickness equal to λ0 / 4, L is the second refractive index film layer SiO with an optical thickness equal to λ0 / 4, and x is a multiple of the low refractive index film layer L with an optical thickness equal to λ0 / 4, and its value is 1.7 to 2.5, with a value interval of 0.1. The first refractive index film layer and the second refractive index film layer are overlapped to form a first reflection layer and a second reflection layer respectively; the middle layer is composed of multiple layers of the second refractive index film layer. The grating period of the grating is 140nm; the width of the first metal layer between the two bars is 56nm, the height is 100nm, and the material is Au; the width of the bar is 84nm, where the height of the dielectric layer of the bar is 600nm, and the material is SiO, and the height of the second metal layer of the bar is 100nm, and the material is Au.

[0055] When the incident light enters the spectrometer of this embodiment, the polarized light transmission spectra and polarization extinction ratio curves of the TE and TM polarization modes are as follows: Figure 7 As shown. The solid line represents the transmittance of TM polarized light, the dashed line represents the transmittance of TE polarized light, and the dotted line represents the polarization extinction ratio of the spectrometer (TM polarized light transmittance / TE polarized light transmittance). Figure 7 As shown, when the incident light enters the spectrometer of this embodiment, within the application wavelength range of 3.6μm to 4.2μm of the spectrometer, the TM polarized light transmittance is greater than 80%, the bandwidth is about 5nm, and the polarization extinction ratio is as high as 10 6 Therefore, the spectrometer of this embodiment has good spectrum and polarization simultaneous spectrometry capabilities.

[0056] Based on the same inventive concept, the disclosed embodiment also provides a method for preparing a spectroscopic device, which includes: coating a filter on a substrate; coating a layer to be etched and a grating mask pattern on the surface of the filter in sequence, and etching the layer to be etched based on the grating mask pattern to form a dielectric layer of the grating strips; coating metal between the dielectric layers of the grating strips and on the surface of the dielectric layer away from the filter to form a first metal layer and a second metal layer of the grating strips.

[0057] Specifically, Figure 8 FIG. 1 is a schematic diagram of a process for preparing a spectrometer device according to an embodiment of the present disclosure. Figure 8 As shown, the preparation method includes the following steps.

[0058] S801, coating a filter on a substrate. The filter can be any type of filter.

[0059] In some embodiments, a molecular beam epitaxy (MBE) method or a physical vapor deposition (PVD) method may be used to sequentially deposit a film system on a substrate. The expression is (LH) m xL(HL) m-1 H or L (HL) m xH(LH) m structure to form an all-dielectric FP filter, wherein H represents the first refractive index film layer; L represents the second refractive index film layer; m is the number of times the high refractive index film layer and the low refractive index film layer are alternately stacked, and m>2; x is the multiple of the first / second refractive index film layer (H / L).

[0060] S802, a layer to be etched and a grating mask pattern are sequentially plated on the surface of the filter.

[0061] In some embodiments, the filter obtained above is plated to the layer to be etched. To simplify the preparation process, the layer to be etched can be made of the same material as the second refractive index film layer. On the layer to be etched, a photolithography process such as electron beam exposure (EBL) or soft X-ray lithography (XIL), a metal film deposition process such as electron beam evaporation (E-beam), magnetron sputtering (Sputter), or thermal evaporation, and a lift-off process are sequentially performed to obtain a grating mask pattern showing a grating shape.

[0062] S803, etching the layer to be etched based on the grating mask pattern to form a dielectric layer of the gate strips.

[0063] In some embodiments, based on the grating mask pattern, the layer to be etched is etched to the surface of the filter by reactive ion beam etching (RIE) or inductively coupled plasma (ICP) to form a dielectric layer of the grating stripes.

[0064] S804, plating metal between the dielectric layers of the grid bars and on the surface of the dielectric layer away from the filter to form a first metal layer and a second metal layer of the grid bars.

[0065] In some embodiments, metal is plated on the surface of the filter between the dielectric layers of the grid bars and on the surface of the dielectric layer away from the filter by a metal film deposition process such as electron beam evaporation (E-beam), magnetron sputtering (Sputter), or thermal evaporation on the above structure to form a first metal layer and a second metal layer of the grid bars. To simplify the preparation process, the first metal layer and the second metal layer of the grid bars can be plated simultaneously in one metal film deposition process, and the thickness of the first metal layer and the second metal layer of the grid bars are consistent.

[0066] After the preparation is completed, the substrate of the spectrometer can be retained, or the spectrometer can be peeled off according to actual needs.

[0067] The principle of solving the problem by the spectrometer prepared by the above preparation method embodiment is the same as that of the above spectrometer embodiment. Therefore, the parameters, materials, or implementation of the preparation method embodiment can refer to the above spectrometer embodiment, and the repeated parts will not be repeated.

[0068] In some embodiments, since the atomic structure of the metal is different from that of the medium, the intermolecular force between them is weak and the adhesion is poor. Therefore, in order to improve the adhesion between the second metal layer of the grid and the dielectric layer, and the adhesion between the first metal layer and the surface of the filter, before plating metal thereon, an adhesion metal layer can be plated on the surface of the filter between the dielectric layers of the grid and the surface of the dielectric layer away from the filter. The material of the adhesion metal layer includes but is not limited to Ti or Cr, and the thickness is 5 to 20 nm.

[0069] In the spectrometer prepared by the above preparation method embodiment, the grating is set on one side of the filter, the grating characteristics are used to split the polarization of the incident light, and the filter characteristics are used to split the spectrum of the incident light, thereby realizing simultaneous spectral and polarization splitting; at the same time, the multi-layer structure of the grating can further suppress the polarized light parallel to the grating direction, thereby improving the polarization splitting effect; in addition, the spectrometer provided by the embodiment of the present disclosure integrates the spectral spectrometer and the polarization spectrometer into one, thereby solving the problem of large size and poor stability of the spectrometer in the related art.

[0070] The above description is only a specific implementation mode of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure.

Claims

1. A spectroscopic device, characterized in that: include: A filter, used for filtering the first incident light into light of at least one specific wavelength; as well as A grating disposed on one side of the filter, used for filtering the second incident light into light of a specific polarization direction; The grating includes a plurality of bars distributed in a linear array and a first metal layer located between the plurality of bars, and the bars include a dielectric layer and a second metal layer covering a surface of the dielectric layer away from the filter.

2. The optical splitter according to claim 1, characterized in that: The filter comprises: a first reflective layer, an intermediate layer and a second reflective layer, the intermediate layer comprises a first surface and a second surface arranged in parallel, the first reflective layer is stacked on the first surface, and the second reflective layer is stacked on the second surface.

3. The optical splitter according to claim 2, characterized in that: The first reflective layer includes a plurality of overlapping first refractive index film layers and second refractive index film layers, and the second reflective layer includes a plurality of overlapping first refractive index film layers and second refractive index film layers; Wherein, the refractive index of the first refractive index film layer is greater than the refractive index of the second refractive index film layer.

4. The optical splitter according to claim 2, characterized in that: The optical thickness of the first reflective layer and the second reflective layer are equal and are one quarter of the applied wavelength of the filter; the optical thickness of the intermediate layer is an integral multiple of one half of the applied wavelength.

5. The optical splitter according to claim 2, characterized in that: The intermediate layer includes a plurality of stepped portions arranged in parallel, and the thicknesses of the plurality of stepped portions are not completely the same, so as to form a plurality of spectral splitting channels.

6. The optical splitter device according to any one of claims 1 to 5, characterized in that: The thickness of the dielectric layer is greater than the thickness of the first metal layer, and the difference between the thickness of the dielectric layer and the thickness of the first metal layer is 4n times the application wavelength of the filter. TE An odd multiple of one, where 4n TE is the equivalent refractive index of TE polarized light.

7. The optical splitter according to claim 6, characterized in that: The ratio of the width of the grating stripes to the grating period of the grating stripes is 1:10 to 9:

10.

8. The optical splitter device according to any one of claims 1 to 5, characterized in that: The plurality of grating strips are arranged in parallel and equidistantly, and the grating period of the grating strips is less than one fifth of the application wavelength of the filter.

9. A method for preparing a spectroscopic device, characterized in that: include: coating a filter on a substrate; The layer to be etched and the grating mask pattern are sequentially plated on the surface of the filter, and based on the grating mask pattern, the layer to be etched is etched to form a dielectric layer of the grating stripes; Metal is plated between the dielectric layers of the grid bars and on the surface of the dielectric layer away from the filter to form a first metal layer and a second metal layer of the grid bars.

10. The method according to claim 9, characterized in that Before metal is plated between the dielectric layers of the grating strips and on the surface of the dielectric layer away from the filter, the method further comprises: An adhesion metal layer is plated between the dielectric layers of the grid bars and on the surface of the dielectric layer away from the filter. The material of the adhesion metal layer includes: Ti or Cr.

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