CN100487521C - Method of reilizing electromagnetic wave function appliance based on metal micro nano structure - Google Patents

Abstract

The invention is a method for realizing electromagnetic wave functional device based on metal micro-nano structure, firstly according to the requirement of the required functional device for outgoing light field, designing substrate material and metal layer structural parameters, and according to the diffraction theory, finding the phase relation of the surface of the functional device; then using the optical axis of the functional device as a center to arrange metallic through hole, and according to the requirement for surface plasma enhancement, arranging a plurality of grooves or concave holes on two sides of or around the through hole, according to the directional requirement of the outgoing light field, calculating the structural parameters of each groove or concave hole; and finally with the depth trace of the grooves or concave holes as a period, repeating them, thus composing the metal micro-nano structural array functional device. The invention breaks through the restriction of diffraction limit and provides an important means for nano optical and nano electronic researches.

Description

Realize the method for electromagnetic wave function element based on metal micro-nanostructure

Affiliated technical field

The present invention relates to utilize metal micro-nano structure that the input electromagnetic wave is modulated, realize the method for various electromagnetic waves (light wave) function element (polarisation, focus on, disperse).

Technical background

The existence of diffraction limit in the traditional optical, make people can't be normally to observing and imaging less than the structure of wavelength below half.So people are devoted to solve diffraction limit restricted problem always.Recently, people such as T.W Ebbesen find, light by the sub-wavelength metallic hole array unusual transmission enhancing (T.W.Ebbesen can occur at some wavelength, Extraordinary optical transmission throughsub-wavelength hole arrays.Nature, 391,667,1998).Studies show that afterwards, if around independent metal aperture or metal slit, produce the periodicity groove of even depth, then emergent light can have fabulous directivity at some wavelength, and can break through traditional diffraction limit (H.J Lezec, Beaming Light from a Subwavelength Aperture.Science, 297,820,2002), these characteristics are relevant with the existence of surface plasma excimer.

The above-mentioned existing various documents of having delivered: T.W Ebbesen, Squeezing LightThrough Tiny Holes.The Electrochemical Society InterfaceSpring, 15,2003 and L.Martin-moreno, Theory of highly directional emissionfrom a single subwavelength aperture surrounded bu surface corrugations.Phys.Rev.Lett.90,167401,2003, F.J Garcia-Vidal, Multiple Paths toEnhance Optical Transmission through a Single Subwavelength Slit.Phys.Rev.Lett.90,213901,2003 relate to groove or the shrinkage pool shape periodic structure of making certain depth on metal film, by changing the quantity and the cycle of groove or shrinkage pool, light is propagated with the certain energy and the very little angle of divergence in the far field.The deficiency of the method for above-mentioned document introduction is: (1) emergent light is not concentrated in near-field energy, and the uncontinuity in the communication process has limited the application of this phenomenon in device; (2) still lack degree of freedom, make electromagnetic function, be difficult to realize as functions such as deviation, beam split, focusing as the angular modulation of important propagation characteristic.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, a kind of method that realizes the electromagnetic wave function element based on metal micro-nanostructure is provided, it utilizes metal shrinkage pool array or metal groove array (its groove or hole depth change the formation curved surface profile) to realize the direction and the energy of transmission and reflection light field are modulated, thereby realize the special functional devices of various electromagnetic wave scopes, as polarisation, focus on, disperse etc.

Technical solution of the present invention:, finish by following steps based on the method for metal micro-nanostructure realization electromagnetic wave function element:

(1) according to the requirement of required function device (as focusing, polarisation, disperse etc.), the structure of design function device, comprise base material and metal-layer structure parameter, and find the solution the phase relation on function element surface according to Huygens-fresnel diffraction theory, normally at first at the metal level of substrate material surface steaming degree half wavelength thickness, steaming degree metal commonly used is a silver, and base material then depends primarily on transmission peak wavelength, as: infra-red material silicon, visible light material quartz, glass etc.;

(2) be center (straight line of generally getting perpendicular to layer on surface of metal is the function element optical axis) with above-mentioned function element optical axis, metal throuth hole is set, and according to surface plasma enhancing requirement, in above-mentioned metal throuth hole both sides or a plurality of (general 6-8 more suitable) groove or shrinkage pool be set all around, and, comprise width, the degree of depth, the depth Trajectory of groove or shrinkage pool according to direction requirement each groove of calculating of outgoing light field or the structural parameters of shrinkage pool.Usually the width of shrinkage pool or groove is taken as half wavelength, and shrinkage pool or groove cycle are taken into usually penetrates optical wavelength, also can adopt following formula (1)-(4) to calculate.

Groove or shrinkage pool cycle and the degree of depth and phase relation are determined as follows usually around the metal throuth hole:

h _i＝(Df _i-l _ik _SP)/(n _{eff_i}-1) (1)

h _iBe i depth of groove, Df _iBe i the groove calculating according to traditional diffraction theory and the phasic difference at center, l _iFor propagate into the distance of i groove, n along the metal surface from central slit _{Eff_i}By i recess width is formula (2), (3) decision.k _SPFor generating the surface plasma wave wave vector, determine by (4) formula.

n _{eff_i}＝b _{TM_i}/k ₀ (2)

$\tanh (\sqrt{{b_{\mathrm{TM}\_i}}^2-{{\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="C200510012135E00101.png,C200510012135E00102.png"\; state="\{\{state\}\}">k</figure-callout>}}_0}^2{e}_{\mathrm{air}}}{w}_i/2)=\frac{-e_{\mathrm{air}}\sqrt{{b_{\mathrm{TM}\_i}}^2-{{\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="C200510012135E00101.png,C200510012135E00102.png"\; state="\{\{state\}\}">k</figure-callout>}}_0}^2{e}_m}}{e_m\sqrt{{b_{\mathrm{TM}\_i}}^2-{{\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="C200510012135E00101.png,C200510012135E00102.png"\; state="\{\{state\}\}">k</figure-callout>}}_0}^2{e}_{\mathrm{air}}}}---\left(3\right)$

b _{TM_i}Be the transmission of TM ripple in metal seam or i groove, w _iBe the width of i metal groove, k ₀Be incident light wave vector in a vacuum, e _AirBe the specific inductive capacity of vacuum, e _mBe the dielectric function of metal A g, n _{Eff_i}Be the equivalent refractive index of slit and i groove,

$k_{\mathrm{sp}}={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="C200510012135E00101.png,C200510012135E00102.png"\; state="\{\{state\}\}">k</figure-callout>}}_0\&PlusMinus;\frac{2p}{L}---\left(4\right)$

k ₀By being used incident light wave vector, k _SPFor generating the surface plasma wave wave vector, L is the cycle of groove;

(3) depth Trajectory with groove or shrinkage pool is shaped as the cycle, and groove or shrinkage pool are carried out repetition, and the depth Trajectory of groove or shrinkage pool constitutes and can be parabola, hyperboloid or other satisfies the design surface shape of diffraction theory phase relation.

The present invention compared with prior art has following advantage:

(1) compares with existing traditional element, propose to utilize metal micro-nanostructure modulated electromagnetic wave yardstick to form special functional devices.

(2) compared with prior art, adjacent grooves, the shrinkage pool degree of depth change by not changing to certain curved surface track, make the direction control through micro-nano structure outgoing light field become possibility, become the necessary condition of design function device.

(3), realized as receiving lens, the specific function element of prism and array thereof received by adopting the perforate depth Trajectory to become the metal micro-nanostructure of certain curved surface that electromagnetic wave is modulated.

Description of drawings

Fig. 1 is the embodiment of the invention 1 a micro-nano function element section of structure;

1, base material, substrate can also can be metal for nonmetal, 2, be the substrate surface metal level, 3, a series of airports that the degree of depth does not wait, 4 is the depth profile that is made of airport (or other medium holes).Airport (or other medium holes) depth profile can be parabola, also can be other profiles such as hyperboloid.The airport depth profile is a sphere among the embodiment;

Fig. 2 is the embodiment of the invention 1 a micro-nano function element structure vertical view, and 1 is metal material, and 2 is the substrate surface metal level, and 3 is a series of airports that the degree of depth does not wait;

Fig. 3 be the embodiment of the invention 1 midplane ripple by metal construction shown in Figure 1 after, in energy distribution from 1 micron place of exit facet.Horizontal ordinate is a position vector, and 2.5 microns of every big lattice, ordinate are that normalized energy distributes;

Fig. 4 be the embodiment of the invention 1 midplane ripple by metal construction shown in Figure 1 after, in energy distribution from 5 microns places of exit facet.Horizontal ordinate is a position vector, 2.5 microns of every big lattice.Ordinate is that normalized energy distributes;

Fig. 5 be the embodiment of the invention 1 midplane ripple by metal construction shown in Figure 1 after, in energy distribution from 9 microns places of exit facet.Horizontal ordinate is a position vector, 2.5 microns of every big lattice.Ordinate is that normalized energy distributes;

Fig. 6 is the embodiment of the invention 2 micro-nano function element section of structures, 1 is base material, and substrate can also can be metal for nonmetal, and 2 is the substrate surface metal level, 3 is a series of airports that the degree of depth does not wait, and mark 4 is the depth profile that is made of airport (or other medium holes).Airport (or other medium holes) depth profile can be parabola, also can be other profiles such as hyperboloid.The airport depth profile is a sphere among the embodiment 2;

Fig. 7 be the embodiment of the invention 2 midplane ripples by metal construction shown in Figure 6 after, in energy distribution from 6 microns places of exit facet.Horizontal ordinate is a position vector, 2.5 microns of every big lattice.Ordinate is that normalized energy distributes;

Fig. 8 be the embodiment of the invention 2 midplane ripples by metal construction shown in Figure 6 after, in energy distribution from 7 microns places of exit facet.Horizontal ordinate is a position vector, 2.5 microns of every big lattice.Ordinate is that normalized energy distributes;

Fig. 9 be the embodiment of the invention 2 midplane ripples by metal construction shown in Figure 6 after, in energy distribution from 9 microns places of exit facet.Horizontal ordinate is a position vector, 2.5 microns of every big lattice.Ordinate is that normalized energy distributes;

Figure 10 is the outgoing light field position phase demand in the embodiment of the invention 1, and horizontal ordinate unit is a micron, and ordinate is the position phase;

Figure 11 is the outgoing light field position phase demand in the embodiment of the invention 2, and horizontal ordinate unit is a micron, and ordinate is the position phase.

Embodiment

Embodiment 1, and by long depth of focus, the submicron order focal spot spotlight effect of the inventive method realization plane wave, its implementation process is as follows:

(1) present embodiment need adopt micro-nano structure to realize long depth of focus, the submicron order focal spot focusing effect of plane light wave.Because the metal material dielectric function has different responses to the different wave length incident light, at visible light wave range, select argent Ag as metal material, at first at quartz substrate surface evaporation 300 nanometer metallic silvers (standard film thickness generally is taken as half wavelength or is slightly smaller than half wavelength).According to the long depth of focus effect of element, obtain element light field exit facet position by Huygens-Fresnel principle and distribute mutually as shown in figure 10;

(2) be the center with the micro-nano device optical axis, metal throuth hole is set, strengthen requirement, in the metal throuth hole both sides or 6 grooves are set all around according to surface plasma; The optical planar wavelength depth of focus of Shi Xianing, submicron order focal spot spotlight effect calculate the degree of depth of determining each groove as required, and then determine the depth Trajectory of each groove.At first determine well width, determine surface plasma wave wave vector k according to (4) formula then according to lambda1-wavelength _SP, with the required exit facet position correspondence that distributes mutually, determine the degree of depth of groove at last according to (1)～(3), make the outgoing light field satisfy Figure 10 and distribute, selecting radius at last is that 35.4 microns sphere is as the depth Trajectory of groove, as shown in Figure 1, 2.

(3) depth Trajectory with groove is the cycle, and groove is carried out repetition, constitutes the nanoarray element.

(4) adopt the above-mentioned nanoarray element of plane wave vertical incidence, and the light energy distribution of exit facet is tested.Fig. 3 is the light energy distribution apart from 1 micron place of micro-nano structure surface, and Fig. 4 is the light energy distribution apart from 5 microns places of micro-nano structure surface, and Fig. 5 is the light energy distribution apart from 9 microns places of micro-nano structure surface.

Can find out by Fig. 3,4,5, by the degree of depth of groove being carried out the curved surface modulation, micro-nano structure has converged to 10 microns wide plane waves in about 0.5 micron scope, and emergent light all has good focusing effect in 1 micron to 9 microns scope, the micro-nano structure of present embodiment has the characteristics of long depth of focus.

Embodiment 2, are long depth of focus, the submicron order twin-beam spotlight effects of realizing plane wave by the inventive method, and its implementation process is as follows:

(1) present embodiment need adopt micro-nano structure to realize long depth of focus, the submicron order twin-beam focusing effect of plane light wave.Because the metal material dielectric function has different responses to the different wave length incident light, at visible light wave range, the same silver of selecting is as metal material.At first at quartz substrate surface evaporation 300 nanometer metallic silvers, and calculate exit facet light field position and distribute mutually and distribute as Figure 11.

(2) be the center with the micro-nano device optical axis, in the through hole both sides or a plurality of grooves are set all around.The twin-beam spotlight effect of Shi Xianing calculates the degree of depth of determining each groove according to (1)～(4) formula as required, and then determines that the depth Trajectory of each groove distributes to satisfy Figure 11.At last, select radius be 24.625 microns sphere as the depth Trajectory of groove, Fig. 6 is the microstructure of embodiment 2 function original papers.

(3) depth Trajectory with groove is the cycle, and groove is carried out repetition, constitutes the nanoarray element.

(4) adopt the above-mentioned nanoarray element of plane wave vertical incidence, and the light energy distribution of exit facet is tested.Fig. 7 is the light energy distribution apart from 6 microns places of micro-nano structure surface, and Fig. 8 is the light energy distribution apart from 7 microns places of micro-nano structure surface, and Fig. 9 is the light energy distribution apart from 9 microns places of micro-nano structure surface.

Can find out that by Fig. 7,8,9 by depth of groove being carried out the curved surface modulation, micro-nano structure is converged to two-beam with 10 microns wide plane waves, and emergent light all has good twin-beam focusing effect in 1 micron to 9 microns scope.

The present invention only sets forth the function element light-focusing function, other function such as polarisation, disperses etc. that principle is identical therewith.

In addition, groove of the present invention or shrinkage pool are positioned at the metal level upper surface, also can add micrographics again at the metal level lower surface simultaneously and make described function element, and promptly micro-nano structure further strengthens the effect of light.

Claims (3)

1, realize the method for electromagnetic wave function element based on metal micro-nanostructure, it is characterized in that: finish by following steps:

(1) according to the requirement of required function device outgoing light field, designs base material and metal-layer structure parameter, and find the solution the phase relation on function element surface according to Huygens-fresnel diffraction theory;

(2) be the center with above-mentioned function element optical axis, metal throuth hole is set, and strengthen requirement according to surface plasma, in above-mentioned metal throuth hole both sides or a plurality of grooves or shrinkage pool are set, require to calculate width, the degree of depth, the depth Trajectory of each groove or shrinkage pool according to the direction of outgoing light field all around;

(3) depth Trajectory with groove or shrinkage pool is shaped as the cycle, and groove or shrinkage pool are carried out repetition, thereby constitutes metal micro structure nanoarray function element.

2, the method based on metal micro-nanostructure realization electromagnetic wave function element according to claim 1, it is characterized in that: the depth Trajectory of described groove or shrinkage pool constitutes parabola or hyperboloid.

3, the method that realizes the electromagnetic wave function element based on metal micro-nanostructure according to claim 1, it is characterized in that: described groove or shrinkage pool are positioned at the metal level upper surface, at the additional again micrographics of metal level lower surface described function element are further strengthened to the effect of light simultaneously.

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