WO2022036511A1

WO2022036511A1 - Infrared bandpass optical filter and sensor system

Info

Publication number: WO2022036511A1
Application number: PCT/CN2020/109556
Authority: WO
Inventors: 纪登鑫; 沈健
Original assignee: 深圳市汇顶科技股份有限公司
Priority date: 2020-08-17
Filing date: 2020-08-17
Publication date: 2022-02-24

Abstract

An infrared bandpass optical filter (400) and a sensor system (1100). The infrared bandpass optical filter (400) has good performance and comprises: a substrate (410); and a filter laminated layer (420) provided on at least one side of the substrate (410). The filter laminated layer (420) comprises multiple MoS2 layers and multiple low-refractive-index layers which are alternately stacked, and the refractive index of the low-refractive-index layers is smaller than that of the MoS2 layers.

Description

Infrared Bandpass Filters and Sensor Systems

technical field

Embodiments of the present application relate to the field of optics, and more particularly, to infrared bandpass filters and sensor systems.

Background technique

Infrared bandpass filters are important optical devices and are widely used in different occasions. For example, in three-dimensional detection based on Time of Flight (TOF), a near-infrared bandpass filter is usually used to block ambient light, so as to ensure the transmittance of light in the target band, while minimizing the The light in the target band affects the signal-to-noise ratio of the sensor. For another example, in the field of optical communication, it is also necessary to use a near-infrared bandpass filter that includes the wavelength of the optical communication in the passband. With the wide application of infrared bandpass filters, there is an urgent need to improve the performance of infrared bandpass filters.

SUMMARY OF THE INVENTION

The embodiments of the present application provide an infrared bandpass filter and a sensor system, and the infrared bandpass filter has better performance.

In a first aspect, an infrared bandpass filter is provided, the filter comprising:

base; and,

A filter stack disposed on at least one side of the substrate, wherein the filter stack comprises a plurality of MoS ₂ layers and a plurality of low-refractive-index layers alternately stacked, the low-refractive-index layers having a refractive index less than Refractive index of the MoS ₂ layer.

In a possible implementation, the passband of the infrared bandpass filter at least partially overlaps with the wavelength range of 800 nm to 2000 nm.

In a possible implementation, the MoS ₂ layer has an index of refraction between 3.5 and 5.

In a possible implementation manner, the extinction coefficient of the MoS ₂ layer is less than 5×10 ^-3 .

In a possible implementation manner, the MoS ₂ layer is formed by an evaporation process.

In a possible implementation manner, the low refractive index layer is composed of one or more of the following materials: silicon dioxide SiO ₂ , magnesium fluoride MgF, aluminum fluoride AlF, titanium dioxide TiO ₂ , aluminum oxide Al ₂ O ₃ , niobium pentoxide Nb ₂ O ₅ , tantalum pentoxide Ta ₂ O ₅ .

In a possible implementation manner, the refractive index of the low refractive index layer is less than 2.5.

In a possible implementation manner, the optical density value OD of the visible light wavelength band of the stop band of the infrared bandpass filter is greater than 3, and the OD of the infrared wavelength band of the stop band of the infrared bandpass filter is greater than 2.

In a possible implementation manner, the transmittance of the passband of the infrared bandpass filter is greater than 90%.

In a possible implementation manner, the filter stack is disposed on the upper surface side or the lower surface side of the substrate.

In a possible implementation manner, the total number of the multiple MoS ₂ layers and the multiple low refractive index layers is 47 layers and the total thickness is 7.2um.

In a possible implementation manner, the wavelength of the passband of the infrared bandpass filter includes 1550 nm.

In a possible implementation, when the incident angle of the light varies between 0° and 30°, the center wavelength shift of the passband of the infrared bandpass filter is less than 30 nm.

In a possible implementation manner, the optical density value OD of the visible light wavelength band of the stop band of the infrared bandpass filter is greater than 39, and the OD of the infrared wavelength band of the stop band of the infrared bandpass filter is greater than 2.2.

In a possible implementation manner, the transmittance of the passband of the infrared bandpass filter is greater than 99%.

In a possible implementation manner, the infrared bandpass filter further includes: a light absorbing coating, which is arranged on the other side of the substrate and is used to block the infrared bandpass filter located on the stop band. light in the band.

In a possible implementation manner, the filter stacks are disposed on both sides of the substrate, and the filter stacks respectively form a high-pass filter portion and a low-pass filter at the portions located on both sides of the substrate part, the passband of the optical filter is the overlapping part of the passband of the high pass filter part and the passband of the low pass filter part.

In a possible implementation manner, the high-pass filter part includes the multiple MoS ₂ layers and the multiple low-refractive-index layers with a total number of 47 layers and a total thickness of 4.5um; The total number of layers of the plurality of MoS ₂ layers and the plurality of low refractive index layers included in the pass filter part is 23 layers and the total thickness is 4.9um.

In a possible implementation manner, the wavelength of the passband of the infrared bandpass filter includes 940 nm.

In a possible implementation, when the incident angle of light varies between 0° and 30°, the center wavelength shift of the passband of the infrared bandpass filter is less than 10 nm.

In a possible implementation manner, the infrared bandpass filter is applied in three-dimensional detection based on time-of-flight TOF or structured light, or in optical communication.

In a second aspect, a sensor system is provided, comprising:

Light source, used to emit light;

The infrared band-pass filter in the first aspect or any possible implementation manner of the first aspect, the infrared band-pass filter is used to transmit the light emitted by the light source located in the infrared band-pass filter. the portion within the passband; and,

a sensor for detecting the light transmitted by the infrared bandpass filter.

In a possible implementation manner, the sensor system is applied in three-dimensional detection based on TOF or structured light, or in optical communication.

Based on the above technical solutions, the semiconductor material MoS ₂ is applied in the optical field, especially MoS ₂ is used as the material of the high refractive index layer in the infrared bandpass filter, so that the high refractive index material layers and the low refractive index layers are alternately stacked , forming a filter stack to achieve a high-performance infrared bandpass filter. The infrared bandpass filter can have a small center wavelength shift when the incident angle of light changes, and has a high transmittance in the passband.

Description of drawings

FIG. 1 is a schematic structural diagram of a possible infrared bandpass filter involved in an embodiment of the present application.

FIG. 2 is a schematic structural diagram of another possible infrared bandpass filter involved in an embodiment of the present application.

FIG. 3 is a schematic structural diagram of yet another possible infrared bandpass filter involved in an embodiment of the present application.

Figure ₄ is a schematic diagram of the refractive index and extinction coefficient of MoS2.

FIG. 5 is a schematic diagram of an infrared bandpass filter according to an embodiment of the present application.

FIG. 6 is a schematic diagram based on the transmittance curve of the Si:H/SiO ₂ filter shown in FIG. 2 .

FIG. 7 is a schematic diagram based on the transmittance curve of the MoS ₂ /SiO ₂ filter shown in FIG. 2 .

FIG. 8 is a schematic diagram based on the transmittance curve of the Si:H/SiO ₂ filter shown in FIG. 1 .

FIG. 9 is a schematic diagram based on the transmittance curve of the MoS ₂ /SiO ₂ filter shown in FIG. 1 .

FIG. 10 is an enlarged view of the filter shown in FIG. 9 at the passband.

FIG. 11 is an enlarged view of the filter shown in FIG. 9 at the stop band.

FIG. 12 is a schematic diagram of a sensor system according to an embodiment of the present application.

detailed description

The technical solutions of the present application will be described below with reference to the accompanying drawings.

1 to 3 are schematic structural diagrams of several possible types of infrared bandpass filters involved in the embodiments of the present application. Generally, an infrared bandpass filter includes at least a substrate and a filter stack disposed on the substrate, which is also referred to as a filter stack hereinafter, for example, as shown in FIG. 1 . The filter stack is usually formed by alternately stacking high-refractive index layers and low-refractive-index layers, ie, alternating high-refractive-index filter layers and low-refractive-index layers are sequentially formed on a substrate. Wherein, the layer (innermost layer) in direct contact with the substrate can be a high refractive index layer or a low refractive index layer; the layer farthest from the substrate (outermost layer) is usually a low refractive index layer, and the incident light can be, for example, from The outermost low-refractive index layer is incident on the infrared bandpass filter, thereby filtering the light of the non-target wavelength band and transmitting the light of the target wavelength band. It should be understood that the high refractive index and the low refractive index in the embodiments of the present application are relative situations, and it is satisfied that the refractive index n _h of the material of the high refractive index layer is greater than the refractive index n _l of the material of the low refractive index layer, that is, n _h > n _l can be. The high-refractive index layer and the low-refractive index layer are usually formed of different dielectric materials, for example, the infrared bandpass filter may include a Si:H/SiO filter stack, wherein the high _- refractive index layer is made of hydrogenated silicon (Si: H), the low refractive index layer consists of _SiO2 . In addition, it should be understood that the alternately arranged high-refractive index layers and low-refractive index layers may refer to a single-layer material layer formed by processes such as vapor deposition; it may also refer to a multi-layer material layer formed of the same material, that is The high-refractive index layer or the low-refractive-index layer of the layer structure, thereby realizing a functional "single" layer of high-refractive index layer or "single-layer" of low-refractive index layer.

In the infrared bandpass filter shown in Figure 1, the filter stack is only provided on one side of the substrate, but depending on the application and performance requirements, the filter stack can also be provided on both sides of the substrate, such as shown in Figure 2. In Figure 2, the infrared bandpass filter includes a filter stack coated on the upper and lower surfaces of the substrate, respectively. Typically, an infrared bandpass filter of this design includes a high-pass filter section and a low-pass filter section, and the band between the passband of the high-pass filter section and the passband of the low-pass filter overlaps That is, the band-pass band of the infrared band-pass filter. For example, the wavelength of the passband of the high-pass filter part is greater than λ ₁ , the wavelength of the passband of the low-pass filter part is less than λ ₂ , and λ ₁ <λ ₂ , the wavelength of the pass band of the infrared band-pass filter includes λ ₁ to λ ₂ .

The filter stacks of the infrared bandpass filters shown in Figures 1 and 2 utilize the cancellation between the reflections of different stacks to achieve blocking of non-target wavelength bands. The wavelength of the passband of the pass filter has an influence, and formula (1), which will be described later, needs to be considered in the design. Compared with the infrared bandpass filter with single-side design shown in Figure 1, the infrared bandpass filter with double-sided design shown in Figure 2 can make the cut-off wavelength of the long-band lower and the bandwidth of the passband narrower And because the filter stack is arranged on both sides of the substrate, the stress generated by the filter stack can be balanced, and the warpage caused by the stress can be reduced. Therefore, the infrared bandpass filter shown in Figure 2 has better performance.

In some other applications, the infrared bandpass filter may also include a filter stack coated on one side of the substrate, and a light absorbing coating, such as a visible light absorbing coating, on the other side of the substrate, such as shown in FIG. 3 . The light-absorbing coating can effectively increase the optical density (OD) value of the band-stop band, reduce the light transmittance of the band-stop band, and improve the signal-to-noise ratio.

The basic requirement of an infrared bandpass filter is to have high transmittance in the passband, and high blocking rate outside the passband, that is, in the stopband. Among them, the OD value can be used to characterize the blocking rate of the stopband, The larger the OD value, the higher the light blocking rate and the better the light blocking ability.

In addition, for the infrared bandpass filter, when the incident angle of the light changes, the center wavelength of the passband of the infrared bandpass filter is shifted accordingly. In order to reduce the shift of the center wavelength, the width of the passband can be increased, so that the light of the target wavelength within the required incident angle range is all within the passband of the filter. However, such a design will increase the transmitted ambient light, thereby reducing the signal-to-noise ratio, and increasing the width of the passband generally requires an increase in the number of filter stacks, eg, typically about 120-225 layers. The increase in the number of filter stacks affects the cost and fabrication time of the filter, and the larger overall stack thickness also makes the filter difficult to pattern.

Therefore, the present application provides an infrared bandpass filter, which has better performance, especially when the incident angle of the light changes, the shift of the central wavelength of the passband is small, and the passband is The in-band transmittance is greater without increasing the thickness of the filter stack of the infrared bandpass filter.

The infrared bandpass filter of the embodiment of the present application can be applied in various scenarios, for example, in distance detection, three-dimensional detection based on Time of Flight (TOF) or structured light, or optical communication.

FIG. 4 is a schematic block diagram of the structure of an infrared bandpass filter according to an embodiment of the present application. As shown in FIG. 4 , the infrared bandpass filter 400 includes a substrate 410 and a filter stack 420 .

The passband of the infrared bandpass filter 400 may at least partially overlap with the wavelength range of 800 nm to 2000 nm. For example, the wavelength of the passband of the infrared bandpass filter 400 may include 940 nm, or in other words, the center wavelength of the infrared bandpass filter 400 is about 940 nm, for example, it is used in TOF-based three-dimensional detection; or, The wavelength of the passband of the infrared bandpass filter 400 may include 1550 nm, or in other words, the center wavelength of the infrared bandpass filter 400 is about 1550 nm, for example, it is used in optical communication.

The filter stack 420 is disposed on at least one side of the substrate 410 .

The filter stack 420 includes a plurality of MoS ₂ layers and a plurality of low refractive index layers stacked alternately.

Wherein, the refractive index of the low refractive index layer is smaller than the refractive index of the MoS ₂ layer. In other words, the material of each high refractive index layer in the filter stack 420 is MoS ₂ , and the material of each low refractive index layer in the filter stack 420 is a low refractive index material, and the refractive index of MoS ₂ is higher than The refractive index of the low-refractive material.

MoS ₂ is called molybdenum sulfide or molybdenum disulfide, MoS ₂ material is a semiconductor material, it has good lubricity and compressive wear resistance, so it is usually used as a solid lubricant for high speed, heavy load, high temperature, high vacuum As well as equipment operating under working conditions such as chemical corrosion. _In addition, MoS2 is also diamagnetic and can be used as a linear photoconductor and a semiconductor showing P-type or N-type conductivity properties, and has the functions of rectification and transduction. _MoS2 can also be used as a catalyst for the dehydrogenation of complex hydrocarbons. However, for the use of MoS ₂ , it is rarely used in the field of optics, and only single-layer or ultra-thin MoS ₂ is used as a two-dimensional optical material, and its high refractive index has never been used to make infrared bandpass. A filter stack of filters.

MoS2 material has a high refractive index, for example, in the wavelength range of 800nm to _2000nm , its refractive index is between 3.5 and 5, or even between 4 and 5. The extinction coefficient of the MoS ₂ material is also low, eg, less than 5×10 ⁻³ in the wavelength range of 800 nm to 2000 nm.

Table 1 shows the comparison between MoS ₂ material and Si:H, which is the best high-refractive index material at present. It can be seen that the refractive index of MoS ₂ material is significantly higher than that of Si:H material at different wavelengths. Figure 5 shows the change of the refractive index and extinction coefficient of MoS ₂ material with wavelength. It can be seen that MoS ₂ material has a higher refractive index (refractive index, n) and a higher refractive index in the wavelength range of 800nm to 2000nm. Small extinction coefficient (extinction coefficient, k).

Table I

波长(nm)Wavelength (nm)	Si:H的折射率Refractive Index of Si:H	MoS ₂的折射率 Refractive index of _MoS
800nm800nm	3.733.73	4.734.73
840nm840nm	3.703.70	4.594.59
880nm880nm	3.663.66	4.494.49
920nm920nm	3.633.63	4.434.43
960nm960nm	3.613.61	4.394.39
1000nm1000nm	3.593.59	4.344.34

1040nm1040nm	3.573.57	4.304.30
1080nm1080nm	3.563.56	4.294.29
1120nm1120nm	3.553.55	4.274.27

The material of the low refractive index layer is generally low in refractive index, eg, typically, its refractive index is less than 2.5.

The embodiment of the present application does not limit the material of the low refractive index layer, as long as the refractive index of the material is smaller than the refractive index of MoS ₂ . For example, the material of the low refractive index layer may be composed of one or more of the following materials: silicon dioxide SiO ₂ , magnesium fluoride MgF, aluminum fluoride AlF, titanium dioxide TiO ₂ , aluminum oxide Al ₂ O ₃ , pentoxide Niobium Nb ₂ O ₅ , Tantalum Pentoxide Ta ₂ O ₅ . In order to optimize the performance of the infrared bandpass filter 400 , for example, a low-refractive-index material whose refractive index is significantly different from that of MoS ₂ can be selected. Preferably, the material of the low refractive index layer may be SiO ₂ .

In this embodiment, the semiconductor material MoS ₂ is applied in the optical field, especially as the material of the high refractive index layer in the infrared bandpass filter, so as to alternately stack with the low refractive index layer to form a filter stack, A high-performance infrared bandpass filter can be realized. The infrared bandpass filter can have a small center wavelength shift when the incident angle of light changes, and has a high transmittance in the passband.

The principle of using MoS ₂ as the material of the high refractive index layer in the filter stack will be specifically described below. See formula (1) below, where R _AVE is the lowest average reflectance in the passband of the infrared bandpass filter; B=λ _max /λ _min , where λ _max and λ _min are the maximum wavelengths corresponding to the passband, respectively and minimum wavelength; T is the total thickness of the high and low index layers, L is the index of refraction of the outermost layer of the filter stack, which is usually a low index layer, thereby reducing _RAVE ; D=n _h − n _l is the difference between high and low refractive indices.

R _AVE (B,L,T,D)%=(4.378/D)(1/T) ^0.31 [exp(B-1.4)-1](L-1) ^3.5 (1)

It can be seen from formula (1) that in the case of a fixed bandwidth B and a low refractive index material n _l , in order to reduce the reflectivity in the passband of the infrared bandpass filter, it is necessary to increase the total amount of the high and low refractive index layers. Thickness L, or increase the refractive index difference D between the high refractive index layer and the low refractive index layer. Increasing L will lead to the cost and manufacturing time of the infrared bandpass filter, so finding a material with a higher index of refraction is the best choice. Therefore, in this application, MoS ₂ material with higher refractive index is used to replace the material of the traditional high refractive index layer.

Based on formula (1), the present application uses MoS ₂ as the material of the high refractive index layer, which can reduce the reflectance in the passband of the infrared bandpass filter, that is, increase the transmittance. Moreover, it is proved by simulation experiments that the application of MoS ₂ as the material of the high refractive index layer can also reduce the shift of the center wavelength of the infrared bandpass filter with the angle. Therefore, _MoS2 can effectively improve the performance of the infrared bandpass filter as the material of the high refractive index layer.

In addition, since the MoS ₂ layer can be formed by a thermal evaporation process, using the MoS ₂ material as the material of the high refractive index layer in the filter stack of the infrared bandpass filter will make the filter stack The layers are less complex to fabricate, making infrared bandpass filters less expensive. Moreover, when materials such as SiO ₂ are used as the low-refractive index material, since SiO ₂ can also be formed by the evaporation process, the high-refractive index layer and the low-refractive index layer can be formed by the same process, which saves the production time and reduces the cost and easier to mass-produce. For other materials used as high refractive index layers, such as Si:H, which can only be formed by sputtering, i.e. deposition by sputtering in a hydrogen (H ₂ ) atmosphere, Si:H refractive index and extinction The coefficient is related to the hydrogen gas flow rate during sputtering, which is a relatively expensive process.

It can be seen from formula (1) that increasing the difference between the refractive indices of the high refractive index layer and the low refractive index layer of the filter stack can improve the performance of the filter, then in addition to increasing the refractive index of the high refractive index layer In addition to the ratio, the refractive index of the low-refractive index layer can also be lowered. Another benefit of reducing the index of refraction of the low index layer is that the L value in equation (1), the index of refraction of the outermost film, can be simultaneously reduced, further reducing the thickness of the filter stack and thus reducing _RAVE . However, since the low refractive index material used in the current filter scheme is generally SiO ₂ , its refractive index n _l ≈ 1.46, and the refractive index of common low refractive index layers is also greater than 1.2, SiO ₂ and the lowest refractive index The refractive index difference between the materials is much smaller than the refractive index difference between MoS ₂ and Si:H (about 0.7). Therefore, the improvement of the filter performance by replacing the material of the low refractive index layer is not as good as replacing the material of the high refractive index layer with MoS ₂ .

Another consideration is to replace the materials of the high and low refractive index layers at the same time to obtain a larger refractive index difference. At this time, the key consideration should be whether the deposition methods of the two materials with high refractive index and low refractive index are compatible, whether the binding force is sufficient, whether the coefficient of thermal expansion (CTE) is matched, etc., so it is very difficult to achieve. Big.

In view of this, in the embodiments of the present application, efforts are made to find a material that can be used as a high refractive index layer, so as to find a high refractive index material MoS ₂ as a material for the high refractive index layer. The MoS ₂ layer and the commonly used SiO ₂ layer and other low-refractive index layers not only satisfy a large refractive index difference, but also ensure the compatibility of deposition methods, and have good bonding force and stability.

In the infrared bandpass filter 400 of the embodiment of the present application, when the angle of incident light changes, the shift of the central wavelength of the passband is small. For example, for a filter of the type shown in FIG. ₂ , the passband of the infrared bandpass filter 400 using a MoS2 layer as the high refractive index layer varies with the angle of incidence between 0° and 30°. The shift in the center wavelength can be less than 10 nm; as another example, for a filter of the type shown in Figure 1, the IR using the MoS ₂ layer as the high refractive index layer when the angle of incidence varies between 0° and 30° The shift in the center wavelength of the passband of the bandpass filter 400 can be less than 30 nm.

The infrared bandpass filter 400 of the embodiment of the present application has a relatively high transmittance in the passband, and the transmittance can reach more than 90%, which meets the usage requirements of general infrared bandpass filters. In particular, under some designs, the transmission of the passband of the infrared bandpass filter 400 using the MoS ₂ layer as the high refractive index layer can reach more than 99%.

The infrared bandpass filter 400 of the embodiment of the present application has a large OD value in the stop band, wherein the OD value of the visible light band of the stop band can reach 3 or more or 4, and the OD value of the infrared light band of the stop band can reach 3 or more. Reach above 2, which meets the requirements of general infrared bandpass filters. In particular, under some designs, the OD value of the visible light band of the stop band of the infrared bandpass filter 400 using the MoS ₂ layer as the high refractive index layer can reach more than 39, and the OD value of the infrared band of the stop band can reach 39 or more. above 2.2.

6 to 11 , two possible structures when the filter stack 420 of the infrared bandpass filter 400 in the embodiment of the present application is MoS ₂ /SiO ₂ are described in detail, and they are compared with the existing ones including The performance of infrared bandpass filters of Si:H/ _SiO2 filter stacks is compared.

In an implementation manner, the embodiment of the present application provides an infrared bandpass filter 400 based on MoS ₂ /SiO ₂ , and the filter stacks 420 of the infrared bandpass filter 400 are disposed on both sides of the substrate 410 , the filter stack 420 forms a high-pass filter part and a low-pass filter part at the parts located on both sides of the substrate 410, respectively, and the passband of the infrared bandpass filter 400 is the passband and the passband of the high-pass filter part. The overlapping portion of the passbands of the low-pass filter portion.

For example, as shown in Figures 6 and 7, where Figure 6 is an infrared narrow bandpass filter based on Si:H/ _SiO2 , the filter stack of which is Si:H and _SiO2 , respectively As the material of high refractive index layer and low refractive index layer; Figure 7 shows an infrared narrow bandpass filter based on MoS ₂ /SiO ₂ , and the filter stack of this filter is MoS ₂ and SiO ₂ as the Materials for the high-refractive index layer and the low-refractive index layer. Figure 6 shows the transmittance curves of the Si:H/SiO based filter at incident angles of ₀ ° and 30°, and Figure ₇ shows the MoS/SiO based filter at incident angles of 0° and 30° The transmittance curve of the filter of ₂ .

The optical filters shown in FIG. 6 and FIG. 7 include a substrate and filter stacks fabricated on both sides of the substrate, and the center wavelengths of the passbands of the two filters are both about 940 nm. Wherein, the high-pass filter portion of the MoS ₂ /SiO ₂ -based optical filter designed in the embodiment of the present application includes a plurality of MoS ₂ layers and a plurality of low refractive index layers, and the total number of layers is 47 layers and The total thickness is 4.5um, and the total number of the multiple MoS ₂ layers and the multiple low-refractive index layers included in the low-pass filter part is 23 layers and the total thickness is 4.9um.

It can be seen from Figure 6 and Figure 7 that the MoS ₂ /SiO ₂ based filter has higher transmittance in the target band, and the rising and falling edges are steeper than those of the Si:H based filter, making the Filters are less affected by ambient light. Table 2 shows the comparison of the performance parameters of the filter based on Si:H/SiO ₂ and the filter based on MoS ₂ /SiO _2. Table 2 shows the incident angle (Incident Angle), the minimum wavelength (λ) in turn. _min or λ _L ), maximum wavelength (λ _max or λ _H ), center wavelength (Centerλ), center wavelength offset (Center Shift), full width at half maximum (FWHM), maximum transmission of the passband Transmittance (Max Trans.), average transmittance of the passband (Avg.Trans.), and slopes of the rising and falling edges of the passband (slope).

The Si:H/SiO ₂ based filter has a shift of ₁₄ nm in the center frequency wavelength at incident angles of 0° and 30° _; The offset of the center wavelength at 30° is less than 10nm, and the offset of the center wavelength of the designed filter is only 8.8nm when the offset is 10nm, and the offset of 5nm is the target. The offset of the center wavelength of the designed filter is only 7.2nm. Meanwhile, the average transmittance in the FWHM passband of the MoS2/ _SiO2 based filter is about ₆ % higher than that of the Si:H/ _SiO2 based filter in the FWHM passband, and The maximum transmittance in the passband of the filter based on MoS ₂ /SiO ₂ is as high as 99%, which is significantly higher than that of the filter based on Si:H/SiO ₂ of the same type. promote. And the thickness of the filter stack of the MoS ₂ /SiO ₂ based filter is between 1 um and 10 um, which does not bring about a significant increase in the thickness of the filter stack.

Table II

It can be seen that the filter in this embodiment uses the MoS ₂ layer as the high refractive index layer, and its performance is significantly improved, especially in the offset of the center wavelength and the transmittance of the passband.

In another implementation manner, the embodiment of the present application provides an infrared bandpass filter 400 based on MoS ₂ /SiO ₂ , and the filter stack 420 of the infrared bandpass filter 400 is disposed on one of the substrates 410 . side.

Further, optionally, the infrared bandpass filter 400 may further include a light absorption coating 430, and the light absorption coating 430 is disposed on the other side of the substrate 410 for blocking the infrared bandpass filter 400 light in the stop band.

For example, Figure 8 shows a schematic diagram of the transmittance of an infrared narrow bandpass filter based on Si:H/SiO ₂ with an incident angle of 0° and 30°, and the filter stack of the filter is based on Si : H and SiO ₂ are used as the materials of the high refractive index layer and the low refractive index layer, respectively; Figure 9 shows the transmittance of the infrared narrow bandpass filter based on MoS ₂ /SiO ₂ when the incident angle is 0° and 30° Schematic diagram of the filter, the filter stack of the filter is made of MoS ₂ and SiO ₂ as the material of the high refractive index layer and the low refractive index layer, respectively; Figure 10 shows the filter shown in Figure 9 at the passband ; Figure 11 shows an enlarged view of the filter shown in Figure 9 at the stop band.

The optical filters shown in FIGS. 8 to 11 include a substrate and a filter stack formed on the upper surface side or the lower surface side of the substrate, and the passbands of the two filters shown in FIGS. 8 and 9 are The central wavelengths are all around 1550 nm. Wherein, the MoS ₂ /SiO ₂ -based optical filter shown in FIG. 9 to FIG. 11 designed in the embodiment of the present application has a total number of MoS ₂ layers and multiple low-refractive index layers of 47 layers and a total thickness of 47 layers. 7.2um.

It can be seen from Figures 8 and 9 that the transmittance of the stop band of the filter based on Si:H/ _SiO2 is less than 0.5% in the visible light band and less than ₂ % in the infrared band, while the filter based on MoS2/ _SiO2 The transmittance of the stop band of the optical device is close to 0% in the visible light band and less than 0.7% in the infrared band. Table 3 shows the comparison of the performance parameters of the filter based on Si:H/SiO ₂ and the filter based on MoS ₂ /SiO _2. Table 3 shows the incident angle (Incident Angle), the minimum wavelength (λ) in turn. _min or λ _L ), maximum wavelength (λ _max or λ _H ), center wavelength (Centerλ), center wavelength shift (Center Shift), FWHM, OD value in the visible light band of the stop band (VIS OD), and stop band The OD value of the infrared light band (IR OD).

_The MoS ₂ /SiO ₂ based filter has a shift of 35 nm in the center frequency wavelength at incident angles of 0° and 30° _; The shift amount of the central wavelength at ° is less than 30 nm, and the shift amount of the central wavelength of the designed filter is only 27 nm when the shift of 25 nm is targeted. At the same time, it can be seen from Table 3 that the OD value of the stop band of the filter based on MoS ₂ /SiO ₂ in the visible light band is significantly larger than that of the stop band of the filter based on Si:H/SiO ₂ . The OD value, and the OD value of the infrared light band of the stop band of the filter based on MoS ₂ /SiO ₂ is significantly larger than the OD value of the infrared light band of the stop band of the filter based on Si:H/SiO ₂ . It can be seen that the filter based on MoS ₂ /SiO ₂ has a better blocking (absorption and/or reflection) effect on light in the stop band, and blocks the transmission of light in non-target wavelength bands to the greatest extent. At the same time, it can be seen from Figure 10 that the passband transmittance of the MoS ₂ /SiO ₂ -based filter is greater than 99%, and has better transmittance for the light in the target wavelength band; from Figure 11, it can be seen that, The transmittance of the visible light band of the stop band of the MoS ₂ /SiO ₂ based filter is close to 0, and the transmittance of the infrared light band of the stop band is less than 0.7%, so it can better block the light of the non-target band. Also, the thickness of the filter stack of the MoS ₂ /SiO ₂ based filter is less than 10 um, which does not bring about a significant increase in the thickness of the filter stack.

Table 3

It can be seen that in this embodiment, the MoS ₂ layer is used as the filter of the high refractive index layer, and its performance is significantly improved, especially in the offset of the center wavelength and the OD value of the stop band, with a significant improvement.

The designs of the above-mentioned two types of infrared bandpass filters are only examples, and any filter using a MoS ₂ layer as a high refractive index layer should fall within the protection scope of the present application.

To sum up, the design of the infrared bandpass filter of the present application reduces the shift of the center wavelength caused by the incident angle, and does not increase the thickness of the filter stack of the infrared bandpass filter. In some implementations, the width of the rising and falling edges of the passband of the infrared bandpass filter is reduced, and the transmittance to the target wavelength band is increased. In other implementations, the infrared bandpass filter also increases the OD value of the visible light band and the infrared light band in the stop band.

The present application also provides a sensor system, including the sensor system 1100 shown in FIG. 12 . The sensor system 1100 can be applied in distance detection, TOF-based three-dimensional detection, or optical communication.

As shown in Figure 12, the sensor system 1100 includes:

a light source 1110 for emitting light;

The infrared bandpass filter 400 described in any one of the above embodiments is used to pass through the portion of the light emitted by the light source that is located within the passband of the infrared bandpass filter 400; and,

The sensor 1120 is used to detect the light transmitted by the infrared bandpass filter 400 .

The sensor system 1100 may be, for example, a distance sensor system for acquiring the distance of the target; for example, it may be a three-dimensional imaging system based on TOF or structured light, for acquiring a three-dimensional image of the target; for example, it may be used in optical communication for The light of the target band of optical communication is selected, and the light of the non-target band is blocked.

It should be noted that, on the premise of no conflict, each embodiment described in this application and/or the technical features in each embodiment can be arbitrarily combined with each other, and the technical solution obtained after the combination should also fall within the protection scope of this application .

The systems, devices, and methods disclosed in the embodiments of the present application may be implemented in other manners. For example, some features of the method embodiments described above may be omitted or not implemented. The apparatus embodiments described above are only illustrative, and the division of units is only a logical function division. In actual implementation, there may be other division methods, and multiple units or components may be combined or integrated into another system. In addition, the coupling between the units or the coupling between the components may be direct coupling or indirect coupling, and the above-mentioned coupling includes electrical, mechanical or other forms of connection.

Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working process and the technical effect of the above-described devices and equipment may refer to the corresponding process and technical effect in the foregoing method embodiments. No longer.

It should be understood that the specific examples in the embodiments of the present application are only to help those skilled in the art to better understand the embodiments of the present application, rather than limiting the scope of the embodiments of the present application, and those skilled in the art can Various improvements and modifications can be made, and these improvements or modifications all fall within the protection scope of the present application.

The above are only specific implementations of the present application, but the protection scope of the present application is not limited to this. should be covered within the scope of protection of this application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

An infrared bandpass filter, characterized in that the filter comprises:

base; and,

A filter stack is disposed on at least one side of the substrate, wherein the filter stack comprises a plurality of molybdenum disulfide MoS2 layers and a plurality of low - refractive-index layers that are alternately stacked, and the low-refractive-index layers have The refractive index is smaller than that of the MoS 2 layer.
The infrared bandpass filter of claim 1, wherein the passband of the infrared bandpass filter at least partially overlaps the wavelength range of 800 nm to 2000 nm.
The infrared bandpass filter according to claim 1 or 2, wherein the refractive index of the MoS 2 layer is between 3.5 and 5.
The infrared bandpass filter according to any one of claims 1 to 3, wherein the extinction coefficient of the MoS 2 layer is less than 5×10 −3 .
The infrared bandpass filter according to any one of claims 1 to 4, wherein the MoS 2 layer is formed by an evaporation process.
The infrared bandpass filter according to any one of claims 1 to 5, wherein the low refractive index layer is composed of one or more of the following materials:

Silicon dioxide SiO 2 , magnesium fluoride MgF, aluminum fluoride AlF, titanium dioxide TiO 2 , aluminum oxide Al 2 O 3 , niobium pentoxide Nb 2 O 5 , tantalum pentoxide Ta 2 O 5 .
The infrared bandpass filter according to any one of claims 1 to 6, wherein the refractive index of the low refractive index layer is less than 2.5.
The infrared bandpass filter according to any one of claims 1 to 7, wherein the optical density value OD of the visible light band of the stop band of the infrared bandpass filter is greater than 3, and the infrared bandpass filter has an optical density value OD greater than 3. The OD of the infrared band of the pass filter's stop band is greater than 2.
The infrared bandpass filter according to any one of claims 1 to 8, wherein the transmittance of the passband of the infrared bandpass filter is greater than 90%.
The infrared bandpass filter according to any one of claims 1 to 9, wherein the filter stack is provided on the upper surface side or the lower surface side of the substrate.
The infrared bandpass filter according to claim 10, wherein the total number of layers of the plurality of MoS 2 layers and the plurality of low refractive index layers is 47 layers and the total thickness is 7.2um.
The infrared bandpass filter according to claim 11, wherein the wavelength of the passband of the infrared bandpass filter includes 1550 nm.
The infrared bandpass filter according to claim 11 or 12, characterized in that, when the incident angle of the light varies between 0° and 30°, the center wavelength of the passband of the infrared bandpass filter is deviated. shift less than 30nm.
The infrared bandpass filter according to any one of claims 11 to 13, wherein the optical density value OD of the visible light band of the stop band of the infrared bandpass filter is greater than 39, and the infrared band The OD of the infrared band of the pass filter's stop band is greater than 2.2.
The infrared bandpass filter according to any one of claims 11 to 14, wherein the transmittance of the passband of the infrared bandpass filter is greater than 99%.
The infrared bandpass filter according to any one of claims 10 to 15, wherein the infrared bandpass filter further comprises:

The light-absorbing coating, disposed on the other side of the substrate, is used for blocking light in the wavelength band of the stop band of the infrared bandpass filter.
The infrared bandpass filter according to any one of claims 1 to 9, wherein the filter stack is disposed on both sides of the substrate, and the filter stack is located on the substrate The parts on both sides form a high-pass filter part and a low-pass filter part, respectively, and the passband of the optical filter is the overlapping part of the passband of the high-pass filter part and the passband of the low-pass filter part.
The infrared bandpass filter of claim 17, wherein

The high-pass filter part includes the plurality of MoS 2 layers and the plurality of low-refractive index layers with a total number of 47 layers and a total thickness of 4.5um;

The total number of the plurality of MoS 2 layers and the plurality of low refractive index layers included in the low-pass filter part is 23 layers and the total thickness is 4.9um.
The infrared bandpass filter according to claim 18, wherein the wavelength of the passband of the infrared bandpass filter includes 940 nm.
The infrared bandpass filter according to claim 18 or 19, characterized in that, when the incident angle of the light varies between 0° and 30°, the center wavelength of the passband of the infrared bandpass filter is deviated. shift less than 10 nm.
The infrared bandpass filter according to any one of claims 18 to 20, wherein the transmittance of the passband of the infrared bandpass filter is greater than 99%.
The infrared bandpass filter according to any one of claims 1 to 21, wherein the infrared bandpass filter is applied in three-dimensional detection based on time-of-flight TOF or structured light, or in light in communication.
A sensor system, characterized in that it includes:

Light source, used to emit light;

The infrared bandpass filter according to any one of claims 1 to 22, for transmitting a portion of the light emitted by the light source located within the passband of the infrared bandpass filter; and,

a sensor for detecting the light transmitted by the infrared bandpass filter.
The sensor system according to claim 23, wherein the sensor system is applied in three-dimensional detection based on time-of-flight TOF or structured light, or in optical communication.