CN104777532B - Ultra-narrow-band TE (transverse electric) polarizing spectrum selective absorber based on cascaded fiber grating structure - Google Patents
Ultra-narrow-band TE (transverse electric) polarizing spectrum selective absorber based on cascaded fiber grating structure Download PDFInfo
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Abstract
An ultra-narrow-band TE (transverse electric) polarizing spectrum selective absorber based on a cascaded fiber grating structure comprises a metal grating layer and a Bragg grating layer from top to bottom, wherein a metal film reflecting layer is further arranged under the Bragg grating layer; the period of the metal grating layer at the top is 365-375nm, the duty ratio of the metal grating layer at the top is 0.48-0.52, the thickness of the metal grating layer at the top is 45-55 nm, the Bragg grating layer in the middle is formed by less than five pairs of dielectric slabs with high refractive index and dielectric slabs with low refractive index, the dielectric slabs with the high refractive index and the dielectric slabs with the low refractive index are arranged in a staggered manner, the thickness of each dielectric slab with the high refractive index is 270-290 nm, the thickness of each dielectric slab with the low refractive index is 300-320 nm, and the thickness of the metal film reflecting film at the bottom is larger than the skin depth of light in the infrared band. The ultra-narrow-band TE polarizing spectrum selective absorber based on the cascaded fiber grating structure can be processed by an electron-beam direct writing device with a microelectronics technology, the materials are convenient to obtain, the manufacturing cost is low, mass production can be realized, and the absorber has broad practical prospect.
Description
Technical field
This patent is related to ultra-narrow band spectrum selective absorbing device, particularly a kind of ultra-narrow band TE based on cascaded fiber grating structure
Polarization spectrum selective absorbing device.
Background technology
Under normal circumstances, absorber is divided into two kinds：One kind is broad band absorber, and it all has in certain bandwidth range
Very high absorption, is mainly used in field of thin film solar cells；Another kind of spectral selection absorber, that is, in narrower bandwidth
Inside there is preferable absorption, be mainly used in designing highly sensitive detector, heat imaging device and narrow-band absorption/heat radiation
Device.Absorb it has been proposed that many sub-wavelength structures, such as Meta Materials, metal nano to realize preferable spectral selection
Particle etc..In the structure that these are proposed, one-dimensional metal optical grating construction may also used to realize strengthening absorb, and its
Structure is simple, design and making are all more prone to.By simple optimizing, it can realize nearly 100% reason in resonance wave strong point
Want to absorb, and compact conformation, there is in very wide ranges of incidence angles good optical property.Therefore, it is as new
Absorb device to be with a wide range of applications.Meanwhile, according to Kiel Kirchhoff law, the thermal radiation property of a structure can
With by its absorption characteristic direct derivation out.Thus an absorber having desirable absorption characteristic can also regard a reason as
The heat radiator thought.
Existing selective absorbing device is generally made up of three parts, and top is a sub-wavelength structure, and middle is an electricity
Buffer layer, bottom is a metallic film.But these selective absorbing devices, whether based on complicated metamaterial structure
Or simple metal grating structure, suffers from common defect：(bandwidth is usual for poor, the limited narrow-band spectrum of spatial coherence
For hundred nanometer scale, not enough is narrow).In order to reduce the Absorber Bandwidth of selective absorbing device, Y.Gong et al. proposes electricity
Buffer layer and metallic film are replaced with Bragg grating, that is, form the combinative structure of metal grating and Bragg grating, and
Narrow-band absorption/the heat radiator of one TM polarization based on this structure design, it has extremely narrow Absorber Bandwidth (20 nanometers of left sides
Right) and high spatial coherence【Formerly technology 1：Y.Gong,et al.,Phys.Rev.B 87,205121(2013)】.But
It is that this TM polarization narrow-band absorption/heat radiator has a very big defect, its Bragg grating is generally by 20 pairs of high index of refraction electricity
Dielectric layer and low-refraction dielectric layer are constituted, thus it makes complexity, relatively costly, are unfavorable for practical application.
Rectangular raster typically utilizes micro-nano technology technique, the grating with rectangle flute profile processing on substrate.Sub-
Wavelength rectangular grating diffration problem is it is impossible to be processed by simple scalar optical grating diffraction, and must adopt the wheat of vector form
Ke Siwei equation simultaneously combines boundary condition, is accurately solved by the computer program of coding.Moharam et al. has given sternly
The algorithm of lattice coupled-mode theory【Formerly technology 2：M.G.Moharam et al.,J.Opt.Soc.Am.A.12,1077
(1995)】, the Diffraction Problems of this kind of sub-wave length grating can be solved.
Content of the invention
The technical problem to be solved in the present invention is to provide a kind of ultra-narrow for infrared band based on cascaded fiber grating structure
Band TE polarization spectrum selective absorbing device, when light vertical incidence, in the range of its pole narrow-band near centre wavelength
Incident illumination will be absorbed, and with the change of structural parameters, absorption spectrum can occur frequency displacement, and peak absorbtivity wavelength can occur frequency therewith
Move, but nearly 100% absorption can be remained at each peak wavelength, and the full width at half maximum of absorption line is less than 20 always
Nanometer.Simultaneously for different incident wavelengths, it absorbs angle difference, and the increase with angle, and the width of angular spectrum is quick
Reduce, there is very high spatial directivity, similar to the characteristic of antenna.Therefore, this ultra-narrow band spectrum selective absorbing utensil has
Important practical value.
The technical solution of the present invention is as follows：
A kind of ultra-narrow band TE polarization spectrum for infrared band (1800-2200nm) based on cascaded fiber grating structure selects
Property absorber, this absorber includes top-down metal grating layer and Bragg grating layer it is characterised in that in described cloth
Also has metal film reflector layer, described cycle of top metal grating layer, dutycycle and thickness are respectively under glug grating layer
365～375 nanometers, 0.48～0.52 and 45～55 nanometer, described middle Bragg grating layer is staggered to following by 5
High index of refraction dielectric slabs and low-refraction dielectric slabs composition, described high index of refraction dielectric slabs and low refraction
The thickness of rate dielectric slabs is respectively 270～290 nanometers and 300～320 nanometers, described bottom metallic film reflecting layer
Thickness should be greater than the skin depth in infrared band for the light.
Described cycle of top metal grating layer, dutycycle and thickness are respectively 370 nanometers, 0.5 and 50 nanometer, described
Middle Bragg grating layer be 5 to staggered high index of refraction dielectric slabs and low-refraction dielectric slabs, described
High index of refraction dielectric slabs and the thickness of low-refraction dielectric slabs be respectively 280 nanometers and 311 nanometers, described bottom
The thickness of portion's metal film reflector layer is 200nm.
Compared with prior art, the technique effect of the present invention is as follows：
1st, particularly when cycle of the top metal grating layer of absorber, dutycycle and thickness be respectively 370 nanometers, 0.5
With 50 nanometers, middle Bragg grating layer is 5 staggered high index of refraction dielectric slabs and low-refraction electrolyte to be put down
Plate, the thickness of high index of refraction dielectric slabs and low-refraction dielectric slabs is respectively 280 nanometers and 311 nanometers, bottom gold
When the thickness belonging to thin film reflective layer is for 200nm：
When infrared band light vertical incidence then, incident illumination in the range of its pole narrow-band near centre wavelength
To be absorbed, close to 100%, full width at half maximum is less than 20nm to peak absorbance rate, for different incident wavelengths, it absorbs/radiation
Angle is different, and the increase with angle, and the width of angular spectrum quickly reduces, and has very high spatial directivity, similar to sky
The characteristic of line.
2nd, the present invention has flexible and convenient to use, peak absorbance rate height, the full width at half maximum very little of absorption and spatial coherence
Preferably the advantages of, be that a kind of ideal spectral selection absorbs device, straight using optical holographic recording technology or electron beam
Write device combines Microelectronic etching technique, can high-volume, produce at low cost, absorption device stable performance after making, can
Lean on, there is important practical prospect.
Brief description
Fig. 1 is the TE polarization spectrum selective absorbing device for infrared band based on cascaded fiber grating structure of the present invention
Geometry.
In figure, 1 represents region 1, and (refractive index is n1), 2 represent metal grating layer, and 3 represent Bragg grating layer, by N (N≤
5) to staggered high index of refraction dielectric slabs, (refractive index is nh) and low-index layer dielectric slabs (refractive index be nl)
Composition, nh<nl, 4 represent metal grating reflecting layer, and material is as top metal grating layer.(direction of an electric field is along y for TE polarized light
Axle) from region 1 this device incident.D is the metal grating cycle, and f is metal grating dutycycle, and h is metal grating thickness, haAnd hb
It is respectively the high refractive index layer of Bragg grating and the thickness of low-index layer, the thickness of bottom metallic film is taken as 200nm.
Fig. 2 is that during the TE polarized light vertical incidence of an embodiment in the range of application claims, device absorbance becomes with wavelength
The curve changed.
Fig. 3 is the change curve with angle of incidence for absorbance during three discrete wavelengths incidence of embodiment in Fig. 2.
Specific embodiment
With reference to embodiment and accompanying drawing, the invention will be further described, but should not limit the protection model of the present invention with this
Enclose.
First refer to Fig. 1, Fig. 1 is that the ultra-narrow band TE for infrared band based on cascaded fiber grating structure of the present invention polarizes
The geometry of spectral selection absorber.In figure, region 1 is uniform, is air (refractive index n1=1).TE polarized light with
Certain angle θ incides this device, and TE polarized light corresponds to the direction of vibration of electric field intensity perpendicular to the plane of incidence, i.e. y-axis.
As seen from the figure, the present invention is used for the ultra-narrow band TE polarization spectrum selectivity based on cascaded fiber grating structure of infrared band
Absorber, it includes top-down metal grating layer 2, Bragg grating layer 3, and metal film reflector layer 4, top metal
The cycle of grating layer, dutycycle and thickness are respectively 365～375 nanometers, 0.48～0.52,45～55 nanometers, middle Prague
Grating layer is made up of to staggered high index of refraction dielectric slabs and low-refraction dielectric slabs N (N≤5), its thickness
It is respectively 270～290 nanometers, 300～320 nanometers, the thickness in bottom metallic film reflecting layer should be greater than light in infrared band
Skin depth.
Under geometry as shown in Figure 1, the present invention adopts rigorous coupled wave approach【Formerly technology 2】Calculate this to surpass
Absorption efficiency in the range of infrared band for the arrowband TE polarization spectrum selective absorbing device.We utilize rigorous coupled wave approach
【Formerly technology 2】With simulated annealing rule【Formerly technology 3：W.Goffe et al.,J.Econometrics 60,65-99
(1994)】It is optimized, thus obtaining the structural parameters of this ultra-narrow band TE polarization spectrum selective absorbing device.
A specific embodiment of the present invention is given below, now the material in top metal grating and bottom metal reflecting layer
For golden (Au), its dielectric constant is described by Drude model：
Wherein, π ν in ω=2 represents the angular frequency of incident plane wave, and ν represents frequency, ωp=1.32 × 1016rad/s,ωc
=1.2 × 1014rad/s.
Bragg grating by 5 pairs of highs index of refraction aluminium sesquioxide (Al2O3) and low-refraction fused quartz (SiO2) put down
Plate is staggered and forms, and their refractive index is respectively 1.74 and 1.45.The cycle d=370nm of top metal grating, dutycycle
F=0.5, the thickness of grating is h=50nm, the Al of Bragg grating2O3And SiO2The thickness of layer is respectively ha=280nm and hb=
311nm, the thickness of bottom metallic film is 200nm.
Table 1 gives the present invention a series of embodiment, λmaxRepresent the peak wavelength of each absorption spectrum, AmaxRepresent absorbing light
Absorption efficiency at the peak wavelength of spectrum, FWHM represents the full width at half maximum (FWHM) of transmitted spectrum.
Fig. 2 is the song with wavelength change for the absorbance of device during the TE polarized light vertical incidence of one embodiment of the invention
Line, as seen from the figure, the light in the range of an extremely narrow wavestrip near centre wavelength 1958.5nm will be absorbed, central wavelength
Peak absorbance be 99.96%, the full width at half maximum (FWHM) (FWHM) of transmitted spectrum is 16nm.
Fig. 3 is the change curve with angle of incidence for absorbance during three discrete wavelengths incidence of Fig. 2 embodiment, can from figure
To find out, for different incident wavelengths, absorption/radiation angle is different, and in figure incident wavelength is respectively λ1=1958.5nm, λ2=
1864nm and λ3=1661nm, their peak absorbance/radiation angle is respectively 0 °, 30 ° and 60 °, and angular breadth is respectively 18 °,
2.5 ° and 1.7 °, there is good spatial directivity, similar to traditional antenna performance.
When making the ultra-narrow band TE polarization spectrum selective absorbing device based on cascaded fiber grating structure for the present invention, suitably select
The thickness of high low-index layer of the cycle of top metal grating, dutycycle and thickness and Bragg grating and refractive index can
With spectral line width and the good ultra-narrow band TE polarization spectrum selective absorbing device of spatial directivity of being absorbed.
The ultra-narrow band TE polarization spectrum selective absorbing device based on cascaded fiber grating structure of the present invention, has using flexibly side
Just, the advantages of absorption spectrum line width, high spatial good directionality, it is a kind of ideal absorption device, using optical holographic
Recording technique or electron-beam direct writing device combine Microelectronic etching technique, can high-volume, produce at low cost, the absorption of making
Device stable performance, reliability, have important practical prospect.
Absorption efficiency at peak wavelength during table 1 TE polarized light vertical incidence
Claims (2)
1. a kind of ultra-narrow band TE polarization spectrum selective absorbing device for infrared band based on cascaded fiber grating structure, this absorption
Device includes top-down metal grating layer (2) and Bragg grating layer (3) it is characterised in that in described infrared band being
1800-2200nm, also has metal film reflector layer (4), described top metal grating under described Bragg grating layer (3)
The cycle of layer, dutycycle and thickness are respectively 365～375 nanometers, 0.48～0.52 and 45～55 nanometer, described middle Bradley
Lattice grating layer is formed to following staggered high index of refraction dielectric slabs and low-refraction dielectric slabs by 5, described
High index of refraction dielectric slabs and low-refraction dielectric slabs thickness be respectively 270～290 nanometers and 300～320 receive
Rice, the thickness in described bottom metallic film reflecting layer is more than the skin depth in infrared band for the light.
2. the ultra-narrow band TE polarization spectrum for infrared band based on cascaded fiber grating structure according to claim 1 selects
Property absorber it is characterised in that described cycle of top metal grating layer, dutycycle and thickness are respectively 370 nanometers, 0.5 and
50 nanometers, described middle Bragg grating layer is 5 to staggered high index of refraction dielectric slabs and low-refraction electricity Jie
Matter flat board, the thickness of described high index of refraction dielectric slabs and low-refraction dielectric slabs is respectively 280 nanometers and 311 to be received
Rice, the thickness in described bottom metallic film reflecting layer is 200nm.
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