CN113759450A

CN113759450A - Polarized light sensitive long wave infrared sub-wavelength grating MDM ladder-shaped structure absorber

Info

Publication number: CN113759450A
Application number: CN202111058218.9A
Authority: CN
Inventors: 郑妍; 张刘; 孙秋香; 朱杨; 吕雪莹; 李博楠
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2021-09-09
Filing date: 2021-09-09
Publication date: 2021-12-07
Anticipated expiration: 2041-09-09
Also published as: CN113759450B

Abstract

The invention discloses a polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder-shaped structure absorber, which comprises a zinc sulfide substrate, wherein an aluminum film is plated at the bottom of the substrate, and a ladder-shaped grating structure layer which is sequentially provided with the aluminum film, a zinc selenide film, the aluminum film, a germanium film and the aluminum film from bottom to top is plated at the upper part of the substrate; according to the invention, by adopting a processing technology combining photoetching, etching and coating, the translation regulation and control of the central wavelength of an absorption peak can be realized only by changing the duty ratio or the period of the micro-nano structure, the ultra-wide-angle narrow-band high absorption is realized under multiple azimuth angles, and the simultaneous processing and preparation are realized for the same film layer of multiple groups of strip micro-nano structures in a comprehensive array area. The problems that in the traditional coating process, the order of magnitude of the coating times is increased due to the fact that multiple coatings are coated in time and area sharing modes, the relative parallelism of the multiple strips of dissimilarity coatings is difficult to guarantee and the like are solved, the processing efficiency is improved, the difficulty and complexity of processing and preparing the polarization spectrum spectrometer in the comprehensive array area are reduced, and the novel coating process has innovation significance.

Description

Polarized light sensitive long wave infrared sub-wavelength grating MDM ladder-shaped structure absorber

Technical Field

The invention belongs to the technical field of micro-nano optical devices, and particularly relates to a polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder-shaped structure absorber.

Background

Perfect light absorption is an efficient way to convert light energy into other forms of energy. The absorber is widely applied to various subject fields, is an important means for improving the optical characteristics of the absorber, especially the application of the perfect absorption characteristic to the field of the detector is always concerned by scholars at home and abroad, and therefore becomes an important research hotspot. Maystre et al published information about the total absorption phenomenon they found in diffraction gratings since 1976, which has advanced the subwavelength metal grating structure as ebesen et al discovered 1998 that the anomalous transmission of periodic small-pore metal films at specific wavelengths appears. In 2008, Landy et al conducted an investigation make internal disorder or usurp of a perfect absorber based on artificial electromagnetic material. In 2010, Liu et al designed a metamaterial absorber with an operating frequency band in the infrared band. Until today, the 8 μm to 13 μm band is known to be the atmospheric window, and absorbers of this band play an important role in the fields of infrared detection technology, photon detection, infrared imaging, infrared stealth, thermal emission, solar cells, biosensing, astronomy, spectroscopy, etc. The improvement of the absorption efficiency of the absorption layer of the infrared detector is an important means for improving the performance of the detector, and meanwhile, the surface plasmon resonance technology can be applied to sensing, filtering modulation, surface enhanced Raman scattering and other fields. The device can also provide a necessary polarization spectrum light splitting method for miniaturization and integration of long-wave infrared polarization spectrum detection.

At present, the research on broadband absorption of a long infrared band is more, the research on narrow-band absorption is less, and the prior art can not realize integral narrow-band absorption in a long-wave infrared 7-14um interval and realize narrow-band high absorption under the conditions of a wide incident angle and an ultra-wide azimuth angle, therefore, a finite element analysis method is adopted, a polarized light sensitive sub-wavelength grating MDM structure based on a surface plasmon resonance principle is provided on a grating structure, the problems that the long infrared band has adjustable wide angle and narrow-band high absorption, the center wavelength of an absorption peak can be adjusted under the conditions that the duty ratio or the period is continuously increased, a spectrum absorption curve is in a red shift phenomenon along with the continuous increase of the duty ratio or the period and the parameter values of other structural film layers are not changed are solved, and the wide angle, the narrow-band absorption and the narrow-band high absorption can be realized under the condition of multiple azimuth angles (0-90 degrees), The narrow band is highly absorbent. Therefore, the wide-angle narrow-band high-absorption enhancement device with adjustable polarization light sensitivity, which is suitable for the sub-wavelength grating MDM structure of the long infrared band, is provided, and has important research value and significance in multi-field engineering application.

Under the condition of multi-azimuth expansion, the structure of the invention often needs to adopt a lens design with large relative aperture in order to improve the energy collection efficiency of the infrared polarization spectrum detection system, so that the detector is required to realize high absorption rate and high efficiency response to light incident at a wide angle, the limitation of the conventional slit type spectrometer can be broken through, and the energy utilization rate of the polarization spectrum detection system is greatly improved. By utilizing the optical characteristics of the structure, the difficulty and complexity of micro-nano processing can be greatly reduced, and a plurality of groups of different long-wave infrared narrow-band absorbers can be efficiently processed and prepared. Therefore, the polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder-shaped structure absorber provided by the invention has the advantages of polarization sensitivity, wide angle, ultra-wide azimuth angle, narrow-band high absorption, adjustable working wavelength and the like, and is suitable for integrated application in the fields of infrared detection technology, infrared imaging, infrared stealth, thermal emission, biosensing, spectroscopy and the like.

Disclosure of Invention

The invention aims to provide a polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder-shaped structure absorber to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: the utility model provides a polarized light is sensitive to infrared subwavelength grating MDM trapezium structure absorber of long wave which characterized in that: the zinc sulfide substrate is provided with an aluminum film for plating at the bottom, a grating structure layer is plated on the upper portion of the zinc sulfide substrate and sequentially comprises the aluminum film, a zinc selenide film, the aluminum film, a germanium film and the aluminum film from bottom to top, and the grating structure layer is of a trapezoidal structure.

Preferably, the grating structure is first photo-etched on the upper surface of the zinc sulfide substrate by using a mask lithography process.

Preferably, after the aluminum film, the zinc selenide film, the aluminum film, the germanium film and the aluminum film are respectively plated on the surface of the structure, a lift-off process flow is utilized, wherein after each film is plated, the substrate strip is placed into the degumming solution to be soaked, the thin film outside the strip and the photoresist are stripped off, and the grating structure layers of the aluminum film, the zinc selenide film, the aluminum film, the germanium film and the aluminum film are plated on the bottom of the zinc sulfide base from bottom to top repeatedly.

Preferably, in the photolithography process flow, it takes a long time to complete the photoresist removal and then repeat the photolithography process, thereby ensuring the integrity of the structure.

Preferably, the substrate with the prepared photoetching pattern is placed in vacuum coating equipment, meanwhile, the equipment is placed with a required coating target material, the target material and gas introduced into the cavity react to form a required medium film and a required metal film, then the medium film and the metal film are deposited on the surface of the substrate layer by layer, and the thickness of each layer of film required by the structure is achieved by controlling the deposition thickness of the medium film and the metal film, so that the preparation of the structure is completed. Meanwhile, the trapezoidal angle of the grating structure is accurately controlled, so that the trapezoidal grating structure is realized.

Compared with the prior art, the invention has the beneficial effects that: the MDM structure is processed by adopting the technology of a processing technology combining photoetching, etching and film coating, so that polarization spectrums with different areas and wavelengths under a full array are obtained; under the condition that the thickness and the material of each structural film are not changed, the translation regulation and control of the central wavelength of an absorption peak can be realized only by changing the duty ratio or the period of a micro-nano structure, the high absorption of a super-wide-angle narrow band is realized under multiple azimuth angles, and in a comprehensive array area, the simultaneous processing and preparation can be realized aiming at the same film layer of multiple groups of strip micro-nano structures, so that the problems that the order of magnitude of film coating times is increased due to multiple film coatings in time-sharing and regional areas, the relative parallelism of a plurality of strip dissimilarity film coatings is difficult to ensure and the like in the traditional film coating process are solved; the processing efficiency is improved, the difficulty and complexity of processing and preparing the polarization spectrum light splitting device in the comprehensive array area are reduced, and the method has innovative significance.

Drawings

FIG. 1 is a schematic diagram of a ladder configuration absorber of the present invention;

FIG. 2 is a schematic view of a trapezoidal structure of a multilayer film of the present invention with different gradients;

FIG. 3 is a schematic diagram of absorption efficiency of gradient angle θ according to the present invention;

FIG. 4 is a schematic diagram of the absorption efficiency of the gradient angle θ of the present invention under the condition of the incident angle of 0-90 °;

FIG. 5 is a schematic diagram showing the relationship between the absorption peak of TM polarization and the azimuth angle under the condition of vertical incidence according to the gradient angle θ of the present invention;

FIG. 6 is a schematic diagram of absorption efficiency of different duty ratios under a normal incidence condition of the gradient angle θ according to the present invention;

FIG. 7 is a schematic diagram of absorption efficiency of the gradient angle θ of the present invention at different periods under a normal incidence condition;

FIG. 8 is a schematic view of the processing flow of the present invention

In the figure: 1. a zinc sulfide-based primer layer; 2. an aluminum film layer; 3. and a grating structure layer.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Referring to fig. 1 to 8, the present invention provides a technical solution: a polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder-shaped structure absorber comprises a zinc sulfide substrate 1, an aluminum film 2 for plating is plated at the bottom of the zinc sulfide substrate 1, a grating structure layer 3 which is sequentially composed of the aluminum film, a zinc selenide film, the aluminum film, a germanium film and the aluminum film is plated at the upper part of the zinc sulfide substrate from bottom to top, and the grating structure layer 3 is of a ladder-shaped structure.

In this embodiment, it is preferable that the grating structure is first formed on the upper surface of the zinc sulfide substrate 1 by a mask photolithography process.

In this embodiment, preferably, after the aluminum film, the zinc selenide film, the aluminum film, the germanium film and the aluminum film are respectively plated on the surface of the structure 3, a lift-off process is used, wherein after each film is plated, the substrate strip is placed into a degumming solution to be soaked, the thin film outside the strip is stripped off together with the photoresist, and the grating structure layer 3 of the aluminum film, the zinc selenide film, the aluminum film, the germanium film and the aluminum film is plated on the zinc sulfide base from bottom to top repeatedly.

In this embodiment, preferably, in the photolithography process flow, it takes a long time to complete the photolithography process after removing the photoresist, so as to ensure the integrity of the structure.

In this embodiment, preferably, the substrate with the prepared photolithographic pattern is placed in a vacuum coating apparatus, the apparatus is placed with a target material for coating, the target material and the gas introduced into the chamber react to form a desired dielectric film and a desired metal film, and then the dielectric film and the metal film are deposited on the surface of the substrate layer by layer, and the thickness of each layer of film required by the structure is achieved by controlling the deposition thickness of the dielectric film and the metal film, thereby completing the preparation of the structure. Meanwhile, the trapezoidal angle of the grating structure is accurately controlled, so that the trapezoidal grating structure is realized.

In the case of performing simulation with the same gradient on both sides of the structure while keeping the original structure parameters unchanged, the angles on both sides of the structure are adjusted to generate different gradients on the structure, and the geometric model schematic diagram is shown in fig. 2, where the geometric model (a) θ is 90 °, (b) θ is 86 °, (c) θ is 82 °, and (d) θ is 78 °.

Under the condition of vertical incidence and the same structure, when theta is obtained by changing the gradient included angle and is equal to 90 degrees, 99.99 percent of absorption efficiency is obtained at a position of 9 um; at 86 ° θ, 96.19% absorption efficiency at 8 um; at 82 °, 92.49% absorption efficiency at 7 um; at 78 °, there is 97.89% absorption efficiency at 6 um. As shown in fig. 3, the wavelength from right to left in fig. 3(a) refers to the absorption efficiency of the gradient angle θ from 90 ° to 102 °, and it is found by simulation analysis that as the gradient angle decreases, the central wavelength also shifts blue. Fig. 3(b) shows absorption efficiency under normal incidence with gradient angle θ of 90 °, θ of 86 °, θ of 82 °, and θ of 78 °. The absorption efficiency under the incident angle of 0 to 90 ° when the gradient angle is (a) θ is 86 °, (b) θ is 82 °, (c) θ is 78 °, is shown in fig. 4 and table 1. When the gradient angle is (a) θ is 86 °, (b) θ is 82 °, (c) θ is 78 °, the TM polarization absorption peak is related to the azimuth angle under the normal incidence condition, as shown in fig. 5.

The absorption efficiency obtained by varying the duty ratio found that the center wavelength red-shifted with increasing duty ratio. As shown in fig. 6, under the normal incidence condition, when the gradient angle is (a), (b), (c) θ and 78 °, the duty ratios of (a), (b) and (c) in fig. 6 are 0.45, 0.47, 0.5, 0.53, 0.56 and 0.58 from left to right, respectively, and the absorption efficiencies of the corresponding curves are obtained. The absorption efficiency obtained by varying the period was found to be a red shift of the center wavelength with increasing period. As shown in fig. 7, under the normal incidence condition, when the gradient angle is (a), (b), (c), and (c) θ is 86 °, the gradient angle is (a), (b), and (c) θ in fig. 7 is (a), (b), and (c) in the order from left to right, the gradient angle is 3.7 μm, 3.9 μm, 4.1 μm, 4.3 μm, 4.5 μm, 4.7 μm, and 4.9 μm, and the absorption efficiency of the corresponding curves are shown.

In the processing process, a substrate 1 is firstly cleaned, then photoresist 2 is uniformly coated on the surface of a cleaned substrate crystal (namely photoresist is uniformly coated), ultraviolet exposure is further carried out through mask photoetching to obtain a grating structure, photoresist which is not exposed is washed away by using photoresist removing liquid, then coating is further carried out to obtain a coating 4, then stripping is carried out by using lift-off process 5, and then coating is repeatedly carried out on the substrate for multiple times to obtain a trapezoidal grating structure layer, as shown in fig. 8.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a polarized light is sensitive to infrared subwavelength grating MDM trapezium structure absorber of long wave which characterized in that: including zinc sulfide base (1), aluminum film (2) are used in the bottom plating of zinc sulfide base (1), zinc sulfide base (1) upper portion plating is by supreme grating structure layer (3) that are the aluminum film, zinc selenide film, aluminum film, germanium membrane, aluminum film in proper order down, grating structure layer (3) are the trapezium structure.

2. The polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder structure absorber of claim 1, characterized in that: firstly, photoetching a grating structure on the upper surface of a zinc sulfide substrate (1) by utilizing a mask photoetching process.

3. The polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder structure absorber of claim 1, characterized in that: and respectively plating an aluminum film, a zinc selenide film, an aluminum film, a germanium film and an aluminum film on the surface of the structure, and utilizing lift-off process flow, wherein after each film is plated, the substrate strip is placed into the glue removing solution for soaking, the thin films except the strip are stripped together with the photoresist, and the grating structure layer (3) of the aluminum film, the zinc selenide film, the aluminum film, the germanium film and the aluminum film is plated on the bottom of the zinc sulfide base repeatedly from bottom to top.

4. The polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder structure absorber of claim 1, characterized in that: in the photoetching process flow, a longer time is needed to finish the photoetching process after photoresist is removed, so that the structural integrity is ensured.

5. The polarized light sensitive long-wave infrared sub-wavelength grating MDM ladder structure absorber of claim 1, characterized in that: and (3) putting the substrate with the prepared photoetching pattern into vacuum coating equipment, simultaneously putting the equipment into a required coating target material, reacting the target material with gas introduced into the cavity to form a required medium film and a required metal film, then depositing the medium film and the metal film on the surface of the substrate layer by layer, and controlling the deposition thickness of the medium film and the metal film to achieve the thickness of each layer of film required by the structure, thereby completing the preparation of the structure. Meanwhile, the trapezoidal angle of the grating structure is accurately controlled, so that the trapezoidal grating structure is realized.