CN101726470A - Refractive index sensor based on surface plasmon interference and detecting method thereof - Google Patents
Refractive index sensor based on surface plasmon interference and detecting method thereof Download PDFInfo
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- CN101726470A CN101726470A CN200810224628A CN200810224628A CN101726470A CN 101726470 A CN101726470 A CN 101726470A CN 200810224628 A CN200810224628 A CN 200810224628A CN 200810224628 A CN200810224628 A CN 200810224628A CN 101726470 A CN101726470 A CN 101726470A
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Abstract
The invention discloses a refractive index sensor based on surface plasmon interference, belonging to the technical field of optical measurement. The refractive index sensor comprises a substrate, an excitation part, a seam type scattering coupling structure and a seam type interference coupling structure. The invention also discloses a detecting method of the refractive index sensor. A sample to be measured is positioned at one side of the excitation part; a light source positioned at the other side of the excitation part is focused through a focusing part; focused light beams excite two surface plasmons on the upper surface and the lower surface of the excitation part through the seam type scattering coupling structure, and the two Surface Plasmons are independently transmitted to the seam type interference coupling structure for interference; and the refractive index change of the sample to be measured and positioned on the surface of the excitation part is induced according to the change of an interference result.
Description
Technical field
The present invention relates to field of optical measuring technologies, particularly relate to detection based on the refractive index of surface phasmon.
Background technology
Surface phasmon (Surface Plasmon) typically refers to the electromagnetic field surface modes in the metal surface, and its characteristic mainly shows as the electromagnetic field local and forms evanescent field at metallic surface, and propagates along the metal surface.Can realize energy conversion between light and the surface phasmon under certain condition.This makes people can utilize surface phasmon to control in the scope interior focusing of micron and even nanoscale.Therefore generally believe that surface phasmon will obtain important application in the nano-photon technical field, become in recent years focus, attracting numerous scientific research personnel's concern based on the experiment of the various devices of surface phasmon and correlation theory research.
Sensor based on surface phasmon is a kind of device that is widely studied.It depends on the principle that the dielectric properties (refractive index) of medium is located in the metal surface according to the surface phasmon electromagnetic field mode, responds to the variation of place, metal surface medium by the change of measuring the former.Because the various processes of biological or chemical aspect often are exactly the process that material changes, and will inevitably produce change of refractive, thus utilize that index sensor can survey these processes carry out state, reaction velocity and result etc.And refractive index is only relevant with the relative content of material, and is irrelevant with absolute content, so refractive index can be carried out trace detection.Index sensor based on surface phasmon then exactly can make full use of this point, because the uniqueness of surface phasmon device can relatively easily be made microsize just, so only need the detection thing of trace.And, be accompanied by micro-fluidic in recent years and " chip lab " notion and development of technologies, comprise that the various devices of sensor are all developing towards microminiaturized and integrability, this has promoted the research of surface phasmon index sensor more.
The surface phasmon index sensor of reporting both at home and abroad at present is mainly based on three kinds of mechanism: the surface plasmon resonance of metal nanoparticle, and the coupling of surface phasmon excites, and the enhancing of the surface phasmon of nanohole array sees through on the metal film.
Summary of the invention
The purpose of this invention is to provide a kind of index sensor and detection method thereof based on surface plasmon interference, it not only can realize significantly improving of sensitivity, and simple in structure, prepares simple and easyly, and has and is beneficial to integrated unique advantage.
The invention discloses a kind of index sensor based on surface plasmon interference, this sensor comprises: the substrate of transparent material; Be plated in the parts that excite on the substrate by magnetron sputtering, electron beam evaporation or thermal evaporation method, this material that excites parts can be but be not limited to gold, silver and copper and thickness between 50nm-500nm; Utilize the method preparation of focused ion beam (Focused IonBeam) etching exciting seam formula scattering coupled structure that is parallel to each other and seam formula on the parts to interfere coupled structure, its width is less than 800nm, and length is less than 200 μ m, and spacing is greater than 10 μ m.
The invention also discloses a kind of detection method of the index sensor based on surface plasmon interference, this method comprises: exciting parts one side to shelve testing sample; Light source focuses on by focus device at opposite side; Focused beam is exciting the parts upper and lower surface to excite the two-way surface phasmon by seam formula scattering coupled structure, more specifically, focused beam is scattered at seam formula scattering coupled structure place, thereby excited surface phasmon at the lower surface that excites parts, the surface phasmon that excites the parts lower surface then is coupled to the upper surface that excites parts by seam formula scattering coupled structure, thereby excited upper surface; The two-way surface phasmon passes to seam formula interference coupled structure place independently of one another and interferes; The seam formula interferes the surface phasmon at coupled structure place to be coupled as light; Filtering scattered light and amplifying optical signals; Survey output signal, obtain interference strength; Change induction testing sample change of refractive by result of interference.Because the wave vector of surface phasmon is relevant with the refractive index that excites parts surface place medium (being testing sample), if therefore testing sample changes, its refractive index is respective change also, thereby cause the variation of testing sample one side surface phasmon wave vector, cause two-way surface plasmon interference result's change.By learning testing sample change of refractive situation, further learn the situation of change of testing sample again to the detection of result of interference.
According to technical scheme of the present invention, the interference of two-way surface phasmon can be expressed as:
Wherein a is an amplitude, k '
SP=2 π/λ
SPBe the spatial frequency of surface phasmon, λ
SPBe the wavelength of surface phasmon, L is the spacing of two seams,
Be the phase term relevant with the process that excites and be coupled into light of surface phasmon.Footmark 1,2 is represented substrate one side and top dielectric one side respectively.K '
SPProvide by following formula
ε ' wherein
mBe the real part of dielectric constant of metal,
Be the specific inductive capacity of medium, n
dBe the refractive index of medium, λ is the vacuum wavelength of light.Introduce the equivalent refractive index n of surface phasmon
Eff, k '
SP≡ n
Eff(2 π/λ), the intensity of two-way surface plasmon interference is like this
By more than, n
EffWith n
dThe pass be
So work as n
D2When changing, n
Eff2Also can correspondingly change, thereby cause the variation of result of interference.
Technical scheme of the present invention has following advantage: sensor of the present invention is of a size of micron dimension, and the length of its centre joint formula structure can be as small as about 10 μ m; Among the embodiment of detection method of the present invention, need not any optics setting in testing sample one side.But these all make sensor of the present invention have good integration.In addition, about the high magnitude of the common surface phasmon sensor of reporting of refractive index remolding sensitivity that experimental data shows among the embodiment of detection method of the present invention, thereby the application prospect of sensor of the present invention and detection method thereof is very considerable.
In addition, this sensor is combined with suitable biological or chemical technology, promptly can be applicable to the biological or chemical field.For example on the metal film of sensor, adhere to the biological identification molecule that one deck can act on mutually with specific molecular, working as sensor this moment contacts with detected sample, if contain above-mentioned specific molecular in the sample, then these molecules will act on and be combined on the metal film mutually with the identification molecule on the metal film.So the outer dielectric properties of metal film changes, thereby cause surface plasmon interference result's change.Therefore, can learn the situation of bio-molecular interaction according to surface plasmon interference result's change.
Description of drawings
Fig. 1 is the synoptic diagram of the embodiment one of the structure of sensor embodiment of the present invention and detection method of the present invention;
Fig. 2 for the embodiment one of detection method of the present invention by the wavelength of scanned laser actual obtain excite parts top medium to be air the time interference spectum;
Medium is that concentration is respectively 0,0.25%, 0.50%, 0.75%, 1.00%, 1.25% and 1.50% NaCl-H to Fig. 3 above the parts exciting for the embodiment one of detection method of the present invention
2Resulting a series of interference spectums during O solution;
Medium is the NaCl-H of variable concentrations to Fig. 4 above the parts exciting for the embodiment one of detection method of the present invention
2The linear relationship chart of the wavelength of the paddy correspondence of interference spectum and solution refractive index during O solution;
Fig. 5 is the synoptic diagram of the embodiment two of detection method of the present invention.
Embodiment
Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used to illustrate purpose of the present invention, but are not used for limiting scope of the present invention.
The structure of sensor embodiment of the present invention as shown in Figure 1, this sensor comprises: glass substrate 1; The layer thickness that the method for deposited by electron beam evaporation is plated on the substrate is a 200nm gold film 2; Two parallel nano-seams with the method for focused-ion-beam lithography prepares on golden film stitch the wide 100nm that is about, and it is 40 μ m that seam is about, and two seams are about 100 μ m at interval; Wherein, the left side seam is for interfering coupled structure 4, and the right side seam is scattering coupled structure 3.
The embodiment one of detection method of the present invention is as shown in Figure 1: LASER Light Source is tunable (800-900nm) ti sapphire laser continuously, and the laser incident direction is at 45 with golden film, and it is directly to be reflected by golden costal fold for fear of incident light that this angle is set; Laser focuses on the right side seam (scattering coupled structure 3) through a microcobjective, and wherein focus diameter is less than 10 μ m, so light beam can not shine left side seam (interfering coupled structure 4); The surface phasmon (6,7) on gold film two surfaces about in the of 2 is located to be excited at right side seam (scattering coupled structure 3), passes to interfere after (interfering coupled structure 4) stitched in the left side; Surface phasmon is coupled into propagable light again by left side seam (interfering coupled structure 4), therefore can receive detection in the far field; In glass substrate 1 one sides, collect avalanche photodide (detector) by the light that left side seam (interfering coupled structure 4) sends with another microcobjective, more specifically, filter the light of right side seam (scattering coupled structure 3) scattering by spatial filtering, use lock-in amplifier to cooperate chopper that feeble signal is amplified, left side seam (the interfering coupled structure 4) light intensity of locating that detects thus is the intensity of two-way surface plasmon interference; The variation of recording surface plasmon interference intensity in the scanned laser wavelength promptly obtains the interference spectum of surface phasmon.Interference spectum when Fig. 2 is air for golden film 2 tops.
In the present embodiment, use the NaCl-H of variable concentrations
2O solution is used as the medium of different refractivity.NaCl-H
2The refractive index of O solution increases with concentration is linear.The concentration here is meant the mass percent of NaCl with respect to solution.The exemplary NaCl-H that shows of Fig. 3
2The O solution concentration is 0,0.25%, 0.50%, 0.75%, 1.00% respectively, 1.25% and seven interference spectrums of 1.50% o'clock, by among Fig. 3 as can be seen along with the even increase of solution concentration, spectral line moves equably to the left.Fig. 4 is the wavelength of paddy correspondence of interference spectum and the relation of corresponding solution refractive index, data point is an experimental result, straight line is the linear fit of data point, by both present good linear relationship as can be seen among Fig. 4, therefore, can indicate the sample change of refractive according to the moving of paddy corresponding wavelength of interference spectum.Can obtain refractive index sensitivity according to the slope of the straight line of match among Fig. 4 is 4547nm/RIU (RIU represents refractive index unit).
The embodiment two of detection method of the present invention as shown in Figure 5, embodiment two and embodiment one are similar, but in the present embodiment, the detection of output signal 9 is in testing sample 5 one sides.In the present embodiment, the incident direction of focused beam 8 is not required, but require to hold the transparent and regular shape of device of testing sample, still can be detected through behind the testing sample 5 to guarantee flashlight.
The embodiment three of detection method of the present invention is identical with embodiment one or embodiment two, but light source is a wideband light source, and spectrum requires enough wide to contain the scope that interference spectum moves; Detector is a spectrometer; The process that does not need scanning wavelength can immediately obtain interference spectum.Therefore present embodiment is more practical for measuring dynamic biological or chemical process.
The embodiment four of detection method of the present invention is identical with embodiment one or embodiment two, but light source is the fixed wave length monochromatic source.In the present embodiment, not moving but respond to change of refractive by interference spectum by the change of interference strength.
Above embodiment only is used to illustrate the present invention; and be not limitation of the present invention; the those of ordinary skill in relevant technologies field; under the situation that does not break away from the spirit and scope of the present invention; can also make various variations and modification; therefore all technical schemes that are equal to also belong to category of the present invention, and scope of patent protection of the present invention should be defined by the claims.
Claims (10)
1. one kind based on the surface plasmon interference index sensor, it is characterized in that described sensor comprises:
Substrate (1);
Excite parts (2), the described parts that excite are positioned on the described substrate (1);
Seam formula scattering coupled structure (3), described seam formula scattering coupled structure (3) are positioned at the described parts (2) that excite;
The seam formula is interfered coupled structure (4), and described seam formula interferes coupled structure (4) to be positioned at describedly to excite parts (2) and be parallel to each other with described seam formula scattering coupled structure (3).
2. as claimed in claim 1ly it is characterized in that based on the surface plasmon interference index sensor described substrate is the transparent material substrate.
3. as claimed in claim 1ly it is characterized in that the described parts (2) that excite are to be plated in metal film on the described substrate (1) by magnetron sputtering, electron beam evaporation or thermal evaporation method based on the surface plasmon interference index sensor.
4. as claimed in claim 3ly it is characterized in that based on the surface plasmon interference index sensor material of described metal film is gold, silver or copper.
5. as claimed in claim 3ly it is characterized in that based on the surface plasmon interference index sensor thickness of described metal pattern is between 50nm-500nm.
6. as claimed in claim 1 based on the surface plasmon interference index sensor, it is characterized in that it is to utilize the method preparation of focused-ion-beam lithography at described parts 2 lip-deep two the parallel nano-seams that excite that described seam formula scattering coupled structure (3) is interfered coupled structure (4) with described seam formula.
7. as claimed in claim 6ly it is characterized in that based on the surface plasmon interference index sensor width of described two parallel nano-seams is less than 800nm, length is less than 200 μ m, and spacing is greater than 10 μ m.
8. survey the method for refractive index based on the surface plasmon interference index sensor for one kind, it is characterized in that described method comprises:
Testing sample (5) is placed described parts (2) one sides that excite;
Light source focuses on by focus device at described parts (2) opposite side that excites;
Focused beam (8) excites the two-way surface phasmon by seam formula scattering coupled structure (3) in described parts (2) upper and lower surface that excites;
The two-way surface phasmon passes to described seam formula independently of one another and interferes coupled structure (4) to locate and interfere;
The surface phasmon that described seam formula interferes coupled structure (4) to be located is coupled as light;
Scattered light and amplifying optical signals that the described seam formula of filtering scattering coupled structure (3) is located;
Receive and detection output signal (9), obtain interference strength;
Change induction testing sample change of refractive by result of interference.
9. the method based on surface plasmon interference index sensor detection refractive index as claimed in claim 8 is characterized in that the wherein said method of two-way surface phasmon that excites specifically comprises:
Focused beam (8) is located to be scattered in described seam formula scattering coupled structure (3), thereby has excited surface phasmon (7) at the described lower surface of parts (2) that excites;
The described surface phasmon of parts (2) lower surface that excites is coupled to the described upper surface that excites parts (2) by described seam formula scattering coupled structure (3), thereby has excited the surface phasmon (6) of upper surface.
10. the method for surveying refractive index based on the surface plasmon interference index sensor as claimed in claim 8, it is characterized in that, the described method of passing through the change induction testing sample change of refractive of result of interference, specifically comprise: the expression formula of interference strength is
Wherein L is the spacing that described seam formula scattering coupled structure (3) and described seam formula are interfered coupled structure (4), and λ is the vacuum wavelength of light, a
1Be the described amplitude that excites parts lower surface surface phasmon, a
2Be the described amplitude that excites parts upper surface surface phasmon,
For with the described relevant phase term of the process that excites and be coupled into light that excites parts lower surface surface phasmon,
For with the described relevant phase term of the process that excites and be coupled into light that excites parts upper surface surface phasmon, n
Eff1Be the described equivalent refractive index that excites parts lower surface surface phasmon, n
Eff2Be the described equivalent refractive index that excites parts upper surface surface phasmon.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102279170A (en) * | 2011-07-15 | 2011-12-14 | 清华大学 | Integrated surface plasma refractive index sensor and detection and analysis method thereof |
| CN105022004A (en) * | 2015-07-07 | 2015-11-04 | 华南师范大学 | Waveguide magnetic field/current sensor based on surface plasmons and device |
| CN109188576A (en) * | 2018-08-14 | 2019-01-11 | 华东师范大学 | A method of the Ai Li light field based on surface phasmon prepares nano material |
| CN112071205A (en) * | 2020-09-11 | 2020-12-11 | 武汉华星光电半导体显示技术有限公司 | Bonding structure and preparation method thereof, cover plate and preparation method thereof |
| CN113433067A (en) * | 2021-06-29 | 2021-09-24 | 北京大学 | Refractive index sensor based on metal nanometer gap surface plasmon intrinsic radiation |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1269158A2 (en) * | 2000-07-21 | 2003-01-02 | Vir A/S | Coupling elements for surface plasmon resonance sensors |
| WO2005078415A1 (en) * | 2004-02-13 | 2005-08-25 | Omron Corporation | Surface plasmon resonance sensor |
| CN100552829C (en) * | 2007-12-29 | 2009-10-21 | 清华大学 | A kind of device that produces near-field nanometer light beam |
| CN101246123B (en) * | 2008-01-04 | 2012-03-14 | 清华大学 | Long-range surface plasma wave refractive index detecting chip |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102279170A (en) * | 2011-07-15 | 2011-12-14 | 清华大学 | Integrated surface plasma refractive index sensor and detection and analysis method thereof |
| CN105022004A (en) * | 2015-07-07 | 2015-11-04 | 华南师范大学 | Waveguide magnetic field/current sensor based on surface plasmons and device |
| CN109188576A (en) * | 2018-08-14 | 2019-01-11 | 华东师范大学 | A method of the Ai Li light field based on surface phasmon prepares nano material |
| CN112071205A (en) * | 2020-09-11 | 2020-12-11 | 武汉华星光电半导体显示技术有限公司 | Bonding structure and preparation method thereof, cover plate and preparation method thereof |
| CN113433067A (en) * | 2021-06-29 | 2021-09-24 | 北京大学 | Refractive index sensor based on metal nanometer gap surface plasmon intrinsic radiation |
| CN113433067B (en) * | 2021-06-29 | 2022-09-23 | 北京大学 | Refractive index sensor based on metal nanometer gap surface plasmon intrinsic radiation |
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