CN103308964B - Efficient nanometer focusing device achieved through ladder type micron slits - Google Patents
Efficient nanometer focusing device achieved through ladder type micron slits Download PDFInfo
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- CN103308964B CN103308964B CN201310261469.6A CN201310261469A CN103308964B CN 103308964 B CN103308964 B CN 103308964B CN 201310261469 A CN201310261469 A CN 201310261469A CN 103308964 B CN103308964 B CN 103308964B
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Abstract
The invention discloses an efficient nanometer focusing device achieved through ladder type micron slits. The efficient nanometer focusing device achieved through the ladder type micron slits comprises a substrate; a plurality layers of metal films which are sequentially stacked are arranged on the substrate; the micron slit is formed in every layer of metal film; the widths of the micron slits increase from bottom to top and the micron slits are formed into a ladder shape in a longitudinal direction; and a glass substrate with an unlimited thickness is replaced by a medium film with a high refractive index and a limited thickness and the focusing strength is obviously increased due to an FP chamber which is formed in the medium film which is provided with the high refractive index. According to the efficient nanometer focusing device achieved through the ladder type micron slits, sub-structures are longitudinally arranged and accordingly the transverse size of the focusing device is greatly reduced, which are important for achievement for the high density integration of surface plasmons polariton devices; the obtained largest focusing strength value is 5.2 times of the incident light strength and the light spot size is changed into 300 nm; and the longitudinally arranged micron slits provide a new direction for designing surface plasmons polariton nanometer focusing devices.
Description
Technical field
The present invention relates to nanophotonics field, be specifically related to a kind of efficient nano focus device utilizing notch cuttype micrometer slit to realize.
Background technology
The efficiency even increasing optical device is kept while the key strengthening photonic circuit integration density of future generation is to make optical device microminiaturization.But microminiaturized always conflicting with these two aspects of high-level efficiency, so the device that can meet these two aspects will be realized simultaneously, be a very large challenge.And the surface phasmon (SPPs) propagated along metal surface, because it can break through the diffraction limit of light, so have great development potentiality in optical device is microminiaturized.And in the metal construction of sub-wavelength, SPPs has super transmission phenomenon.Therefore people have devised various metal construction based on SPPs and realize nano-focusing.These nano-focusing devices have important application in fields such as nanometer light beam shaping, integrated optics, data storing and Near-Field Radar Imagings.Such as, be used for realizing nano-focusing seam-grid structure it be made up of the nanometer groove of a nano-seam and both sides or medium strip.But because the light focused on mainly comes from this single nano-seam, thus directly through light little, that is the focusing efficiency of these structures can be very low.Afterwards, there is people to propose in theory and go to realize nano-focusing by the structure of multiple nano-seam, which increased incident light transmittance, thus overcame the problem of previous poor efficiency focusing.But in this many nanometers crack structure the width of each nano-seam or the degree of depth all different, so be very difficult to preparation experimentally.In order to solve the problem, a recently new structure, it surrounds multiple nano-seam by single T-shaped micrometer slit both sides and formed, and they have been successfully prepared this structure experimentally, achieve efficient nano-focusing simultaneously.But the nano-focusing device reported all early stages all contains multiple transversely arranged minor structure, the minor structures such as such as nanometer groove, medium strip and nano-seam.In these structures, focus device is all that light by multiple minor structure being scattered carries out coherent phase and grows and successfully realize nano-focusing.So, transversely arranged multiple minor structure substantially increases the lateral dimension of focus device.This makes seam-grid structure, many nanometers crack structure and both sides are about 5 microns, 4 microns and 10 microns by the lateral dimension of the cingens T-shaped micrometer slit structure of multiple nano-seam, and so large lateral dimension is unfavorable for the integrated of optical device.
Summary of the invention
For above-mentioned Problems existing, the present invention proposes one and utilize notch cuttype micrometer slit to go to realize compact, efficient nano-focusing device.
A kind of notch cuttype micrometer slit that utilizes is the object of the present invention is to provide to realize efficient, compact nano-focusing device.
Notch cuttype micrometer slit nano-focusing device of the present invention comprises: substrate; Substrate is provided with the metal multilayer film stacked successively; Micrometer slit is offered in every layer of metal film; Micrometer slit is longitudinally superimposed, and its width increases from bottom to up successively, in the vertical in stairstepping.
Substrate is provided with layer of metal film, and at metal film, central authorities offer micrometer slit, and when TM polarized light is from the back surface incident of micrometer slit, the micrometer slit being arranged in the metal film of optical thickness can support multistage pattern.Owing to having multiple-mode interfence in micrometer slit, so when after the incident micrometer slit of light, focusing behavior occurring.Micrometer slit also can excite SPPs on the metal surface simultaneously.The width of micrometer slit determines the position of focus, and along with the increase of the width of micrometer slit, the position of focus also can be improved thereupon, and namely the width of micrometer slit is larger, and the length of focal length is longer.
Substrate is provided with the double layer of metal film stacked successively, in the first metal film and the second metal film, offers micrometer slit respectively, form notch cuttype micrometer slit.When TM polarized light is from the back surface incident of micrometer slit, intermediate transmission along two micrometer slit in the first metal film and the second metal film goes out two-beam, the width of the thickness of the first and second metal films and each layer micrometer slit can be regulated by finite element numerical simulation, the focal position of this two bundles transmitted light is overlapped substantially.Stack the 3rd metal film again, the long phenomenon of coherent phase that the micrometer slit due to the multiple-mode interfence in the micrometer slit of lower two layers and the superiors produces, define efficient nano-focusing effect.Based on principle above, the width of the thickness of each layer metal film and each layer micrometer slit can be regulated by finite element numerical simulation, thus obtain intensity and the spot size of best focusing.
For the nano-device of metal-dielectric structure, the intensity through light not only can be changed by the structural parameters changing micrometer slit, and can be controlled by the refractive index and thickness changing deielectric-coating.Substitute the glass substrate of infinite thickness with the deielectric-coating of the high index of refraction of limited thickness, focus strength can improve further.This is because Fabry-Perot (Fabry-Perot, FP) the chamber effect in the deielectric-coating of high index of refraction causes.When the thickness of deielectric-coating meets FP chamber resonant condition time, focus strength reaches maximal value.
The material of metal film adopts the noble metal such as gold or silver.
The lateral dimension of notch cuttype micrometer slit nano-focusing device of the present invention is between 1 ~ 5 μm.The thickness of every layer of metal film is between 100nm ~ 1 μm.The width of micrometer slit is between 1 μm-5 μm.It is as follows that notch cuttype micrometer slit nano-focusing device of the present invention produces efficient nano-focusing phenomena principles: owing to having multiple-mode interfence in micrometer slit, incident light is by effectively being focused on after certain thickness micrometer slit; The metal multilayer film stacked successively, the width of micrometer slit increases successively from bottom to up, due to continuous print multiple-mode interfence with the coherent phase that occurs between transmitted light and the SPPs be scattered is long makes focusing effect strengthen; Nano-focusing device of the present invention, the existence due to micrometer slit makes the transmittance of incident light more much bigger than nano-seam, thus makes focus strength more much bigger than micrometer slit; Finally, substitute the glass substrate of infinite thickness with the deielectric-coating of limited thickness, focus strength can improve further because of the FP chamber effect in high refractive index medium film.
Advantage of the present invention:
Notch cuttype micrometer slit of the present invention successfully achieves efficient nano-focusing, early stage, the nano-focusing device of report was made up of various transversely arranged minor structure, and the present invention carries out longitudinal arrangement to micrometer slit, substantially reduce the lateral dimension of focus device like this, thus achieving a ultra-compact efficient nano focus device, this is very important for realizing that surface phasmon device High Density Integration goes the same way.In the present invention, this thinking of longitudinal arrangement minor structure provides new research direction also to design surface phasmon nano-focusing device.
Accompanying drawing explanation
Fig. 1 is the structural representation arranging layer of metal film on substrate;
Fig. 2 (a) is the structural representation of the embodiment one of notch cuttype micrometer slit nano-focusing device of the present invention, b (), at the second metal film under different thickness, focus strength is with the change curve of the width of the micrometer slit in the second metal film;
Fig. 3 (a) is the structural representation of the embodiment two of notch cuttype micrometer slit nano-focusing device of the present invention, and the size that (b) is focus strength and FWHM are along with the width w of the micrometer slit in the 3rd metal film
3the curve map of change;
Fig. 4 (a) is the structural representation of the embodiment three of notch cuttype micrometer slit nano-focusing device of the present invention;
Fig. 4 (b) is for focus strength is along with the change curve of the thickness of deielectric-coating.
Embodiment
Below in conjunction with accompanying drawing, by example, the present invention will be further described.
As shown in Figure 1, at glass SiO
2substrate 0 on one deck first metal film 1 is set, material be gold, thickness t
1=1 μm, offer a micrometer slit in the centre of the first metal film 1, the width of micrometer slit is w
1.When TM polarized light (magnetic vector perpendicular to seam) is from the back surface incident of micrometer slit, this micrometer slit can support multistage pattern.Owing to having multiple-mode interfence in micrometer slit, so when producing focusing after the incident micrometer slit of light.Micrometer slit also can excite SPPs on the metal surface simultaneously.Calculate through the optical field distribution situation after micrometer slit with finite element software ComsolMultiphysics.The wavelength of incident TM polarized light is set as λ=630nm, and gold and the specific inductive capacity corresponding to glass are be not ε
au=-11.815+1.239i and ε
siO2=1.45
2.When incident light from the back surface incident of metal film time, the slit calculating different in width through optical field distribution.In these surfaces of intensity distribution, obviously can see that incident light is by there occurs focusing behavior after micrometer slit.The focusing phenomenon of this light is because incident light, by after micrometer slit, occurs caused by multiple-mode interfence.Such as, when the width of micrometer slit is w
1during=1800nm, focusing light intensity is I=1.8 and the spot size focused on is approximately FWHM (full width at half maximum)=380nm.Here, the light intensity focusing on light intensity incident light has carried out normalization.Along with the position of the increase focus of the width of micrometer slit also can be improved thereupon, as the width w of micrometer slit
1during=1800nm, focal position is just on the surface of metal film.Can realize too when width for other different micrometer slit focusing on, just their focusing length is different.
Embodiment one
As shown in Fig. 2 (a), arrange one deck second metal film 2 below the first metal film 1 again, thickness is t
2.The width w of the micron seam in the first metal film 1
1=1800nm, offers the micrometer slit narrower than width in metal film 1 in the second metal film 2, and the width of micrometer slit is w
2, form two layers of notch cuttype micrometer slit.In order to obtain the width of the micrometer slit in the second optimum metal film 2, calculate for different-thickness t
2the second metal film 2, the size of hot spot and focus strength are along with the width w of micrometer slit
2change curve, as shown in Fig. 2 (b).Numerical evaluation shows, works as w
2=1600nm, t
2when=100nm, focus strength reaches maximal value, and spot size is also close to minimum value simultaneously, and now, focus strength is I=2.9, and it is 1.6 times of the focus strength of the single micrometer slit of layer of metal film.The spot size (FWHM) of this exterior focusing becomes 337nm.In contrast to single micrometer slit, the focus strength of two layers of notch cuttype micrometer slit enhances, and focal beam spot size has diminished.Intermediate transmission along two micrometer slit in the first metal film 1 and the second metal film 2 goes out two-beam, and the focal position (point that intensity is maximum) of this two bundles transmitted light overlaps substantially, and is also substantially identical in their phase place of focus place.Therefore two bundle focused lights of two layers of notch cuttype micrometer slit are long at focal position place generation coherent phase, make to focus on light intensity and strengthen further.
Embodiment two
As shown in Fig. 3 (a), the first metal film 1 arranges one deck the 3rd metal film 3 again, thickness t
3=200nm, the micrometer slit that in ratio first metal film 1, width is wider is offered in centre, and the width of micrometer slit is w
3, form three layers of notch cuttype micrometer slit, improve focus characteristics further.When TM polarized light is from the back surface incident of micrometer slit, the SPPs excited propagates along the surface of the first metal film 1, it can be reflected then scattering by two walls of the micrometer slit in the 3rd metal film 3, the light of scattering interferes effect with the light of previously line focus, and scattered light is long at the focus place coherent phase of the first metal film 1 and the second metal film 2.Fig. 3 (b) is for focus strength and spot size (FWHM) are along with the width w of micrometer slit
3the curve map of change.As shown in the figure, focusing light intensity and spot size (FWHM) all show one-period sexual behaviour, and its oscillation period equals λ
spp=600nm, this is consistent with interference condition; And when focus strength reaches maximal value time, its focal beam spot size is then close to minimum value.As the width w of micrometer slit
3when=2000nm, the effect focus strength long due to coherent phase reaches maximal value 3.3, and spot size becomes FWHM=300nm (< λ/2).
Embodiment three
Substitute the glass substrate of infinite thickness with the deielectric-coating of limited thickness, focus strength can be significantly increased because of the FP chamber effect in high refractive index medium film.As shown in Figure 4, substrate 0 adopts the deielectric-coating of high index of refraction, refractive index n
d=3.5, thickness is t
d, incident light incides the back side of deielectric-coating from air 4.Fig. 4 (b) is for focus strength is along with the change curve of the thickness of deielectric-coating.As shown in the figure, the curve of focus strength presents a kind of phenomenon of periodic oscillation, and this period of oscillation is 90nm=λ/n
d/ 2, consistent with the effect in FP chamber.As the thickness t of deielectric-coating
dtime for 180nm, focus strength has maximal value I=5.2, and namely light wave has occurred that in deielectric-coating coherent phase is long, and now spot size is still FWHM=300nm (< λ/2).This focus strength produces many 9 times of light intensity than by seam-grid structure, and the light intensity that it even produces than the nano-seam array having 65 different in width and the degree of depth is eager to excel, but this nano-seam array structure is difficult to preparation experimentally.The light intensity magnitude that the T-shaped micrometer slit that this notch cuttype micrometer slit and both sides surround multiple nano-seam produces is almost identical, but the lateral dimension of this T-shaped micrometer slit but has 10 μm, is far longer than lateral dimension of the present invention.And the present invention carries out longitudinal arrangement to micrometer slit, make lateral dimension only have 2 μm, this is very important for the High Density Integration realizing surface phasmon device.
Can also continue to superpose metal film on the 3rd metal film, the width of the micrometer slit in metal film increases from bottom to up successively, the width of the thickness of each layer metal film and each layer micrometer slit can be regulated by finite element numerical simulation, thus obtain intensity and the spot size of best focusing.
It is finally noted that, the object publicizing and implementing mode is to help to understand the present invention further, but it will be appreciated by those skilled in the art that: without departing from the spirit and scope of the invention and the appended claims, various substitutions and modifications are all possible.Therefore, the present invention should not be limited to the content disclosed in embodiment, and the scope that the scope of protection of present invention defines with claims is as the criterion.
Claims (9)
1. utilize the nano-focusing device that notch cuttype micrometer slit realizes, it is characterized in that, described notch cuttype micrometer slit nano-focusing device comprises: substrate; Substrate is provided with the metal multilayer film stacked successively; Micrometer slit is offered in every layer of metal film; The width of micrometer slit increases from bottom to up successively, in the vertical in stairstepping; Substrate is provided with the first and second metal films, when TM polarized light is from the back surface incident of micrometer slit, intermediate transmission along two micrometer slit in the first metal film and the second metal film goes out two-beam, regulate the described thickness of the first and second metal films and the width of micrometer slit, the focal position of this two bundles transmitted light is overlapped substantially.
2. nano-focusing device as claimed in claim 1, is characterized in that, the width of described micrometer slit determines the position of focus, the width of micrometer slit larger, and the position of focus is higher.
3. nano-focusing device as claimed in claim 1, it is characterized in that, regulate the thickness of the 3rd metal film on the first and second metal films and the width of micrometer slit, make the scattered light of the micrometer slit in the 3rd metal film long at focus place coherent phase with the light of line focus.
4. nano-focusing device as claimed in claim 1, is characterized in that, described substrate adopts the deielectric-coating of high index of refraction.
5. nano-focusing device as claimed in claim 4, it is characterized in that, the thickness of described deielectric-coating meets Fabry-Perot (Fabry – Perot) chamber resonant condition.
6. the nano-focusing device as described in claim 1,4 or 5, is characterized in that, the material of described metal film adopts noble metal.
7. nano-focusing device as claimed in claim 1, it is characterized in that, the lateral dimension of described nano-focusing device is between 1 ~ 5 μm.
8. nano-focusing device as claimed in claim 1, is characterized in that, the thickness of every layer of metal film is between 100nm ~ 1 μm.
9. nano-focusing device as claimed in claim 1, it is characterized in that, the width of described micrometer slit is between 1 μm ~ 5 μm.
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| CN105424656B (en) * | 2016-01-11 | 2018-04-13 | 中国工程物理研究院流体物理研究所 | A kind of measuring method of angle dependency photonic crystal hydrogen gas sensor |
| CN105607167B (en) * | 2016-03-25 | 2017-10-17 | 厦门大学 | A kind of three-stage surface phasmon lens |
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| US8346039B2 (en) * | 2008-11-05 | 2013-01-01 | Rochester Institute Of Technology | Methods for three-dimensional nanofocusing of light and systems thereof |
| CN103076646A (en) * | 2013-01-30 | 2013-05-01 | 中国科学院光电技术研究所 | Manufacturing method of nanoscale super resolution optical focusing device |
| CN103116226A (en) * | 2013-01-23 | 2013-05-22 | 北京大学 | Submicron surface plasmon polariton beam splitter based on composite cavity structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8346039B2 (en) * | 2008-11-05 | 2013-01-01 | Rochester Institute Of Technology | Methods for three-dimensional nanofocusing of light and systems thereof |
| CN103116226A (en) * | 2013-01-23 | 2013-05-22 | 北京大学 | Submicron surface plasmon polariton beam splitter based on composite cavity structure |
| CN103076646A (en) * | 2013-01-30 | 2013-05-01 | 中国科学院光电技术研究所 | Manufacturing method of nanoscale super resolution optical focusing device |
Non-Patent Citations (2)
| Title |
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| Jianjun Chen et al.Highly efficient nanofocusing based on a T-shaped micro-slit surrounded with multi-slits.《OPTICS EXPRESS》.2012,第20卷(第16期), * |
| Strong Intensity Modulation of Surface Plasmon Polaritons by a Dielectric Layer;Liu Y L et al;《IEEE PHOTONICS TECHNOLOGY LETTERS》;20121024;第24卷(第24期);2214-2217 * |
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