CN104089931A - High sensitivity refractive index sensor based on medium magneto-optic surface plasma resonance - Google Patents

Abstract

A high sensitivity refractive index sensor based on medium magneto-optic surface plasma resonance belongs to the field of optical sensing, a reflecting surface of a prism is provided with a silver layer, and the silver layer is provided with a CeYIG layer. The high sensitivity refractive index sensor can improve the sensitivity of an intensity modulation magneto-optic surface plasma resonance device by one order of magnitude, and has great commercial significance.

Description

Based on the high sensitivity index sensor of medium magneto-optic surface plasma resonance

Technical field

The invention belongs to optical sensing field.Be particularly related to surface plasma resonance technology

Background technology

Sensor based on surface plasma resonance (Surface plasmon resonance, SPR) is a kind of very common sensor, is widely used in the fields such as bio-sensing, integrated optics and chemical sensitisation.Surface plasma resonance is to shake effect at metal with a kind of electronics of dielectric surface and plasma collective, and its form with similar ripple is propagated at metal and dielectric surface, and propagation distance depends primarily on the loss of metal.Its principle is to utilize the high index of refraction of prism to be coupled into surface plasmon mode formula (to meet momentum conservation k0*sin (θ)=kspp, wherein k0 is that free end ripple loses k0=2 π/λ, θ is the angle that light incides prism, kspp is that the ripple of surface plasma-wave loses relevant with dielectric constant of metal real part with the specific inductive capacity of medium), because the change of surface plasma resonance effects on surface refractive index is quite responsive, so generally its precision can reach 10 ^-4magnitude.But for the detection in some little molecules or high precision field, the sensitivity of traditional surface plasma resonance sensor is also nowhere near.

Magneto-optic memory technique is to have magneto-optic (Magneto-Optic, MO) a class functional magnetic material of effect, this class material is in the used time of doing that is subject to magnetic field or magnetic moment, and the electromagnetic property of material can change, thereby makes also to change by the light-transfer characteristic of this material thereupon.The character that represents magneto-optic memory technique in actual model with permittivity tensor, wherein nondiagonal element represents the performance of magneto-optic:

${\mathrm{\ϵ}}_3=\left(\begin{array}{ccc}{\mathrm{\ϵ}}_3^{\′}& -i*{\mathrm{\ϵ}}_3^{\′\′}& 0\\ i*{\mathrm{\ϵ}}_3^{\′\′}& {\mathrm{\ϵ}}_3^{\′}& 0\\ 0& 0& {\mathrm{\ϵ}}_3^{\′}\end{array}\right)$

Magneto-optic surface plasma resonance refers to and adopts above-mentioned magneto-optic memory technique to be combined with traditional SPR, utilizes the isoionic humidification of magnetic field effects on surface, can further improve the sensitivity of sensor, can reach 5 times of common spr sensor, even improves two magnitudes.In current reported literature and commercialization general adopt ferromagnetic material as: cobalt, the materials such as iron are as magnetooptical layer.Though such magnetic material has very strong magnetic, but because its large loss, thereby limit the further raising of device sensitivity.

Summary of the invention

Technical matters to be solved by this invention is that a kind of high sensitivity index sensor compared with prior art with better sensing capabilities is provided.

The technical scheme that the present invention solve the technical problem employing is, based on the high sensitivity index sensor of medium magneto-optic surface plasma resonance, it is characterized in that, is provided with silver layer at the reflecting surface of prism, is provided with CeYIG layer on silver layer.

Further, silver thickness is 41nm, and CeYIG layer thickness is 25nm.

The invention has the beneficial effects as follows:

1, simple in structure, manufacture craft is simple, cost is lower;

2, low-loss, the sensitivity that fundamentally improves device;

3, device material is selected best;

4, medium magnetooptical layer surface hollow structure can further be strengthened specific chemical molecular susceptibility;

5, the sensitivity of the magneto-optic surface plasma resonance device of intensity modulated is improved to an order of magnitude, have very large commercial meaning.

The present invention changes traditional magneto-optic surface plasma resonance device, and working medium magnetooptical layer carrys out the sensing capabilities of enhance device first, has solved the high loss of traditional magneto-optic surface plasma sensor, hyposensitivity, complex structure and other problems.The present invention's application CeYIG low-loss, makes device more responsive; The refractive index that CeYIG is high, pushes mould field to medium magnetooptical layer, has avoided the loss that metal is high; The magneto-optical property that CeYIG is high, makes the field enhancement effect of matallic surface layer stronger; Utilize medium magnetooptical layer as sensing layer, because dielectric layer surface hollow structure can further be strengthened specific chemical molecular susceptibility.Utilize silver near 1000nm wavelength, to have low loss, and CeYIG has high magneto-optic effect near 1000nm wavelength, both perfect combination, can further improve device sensitivity simultaneously.This device is intensity modulation type sensor, and its resolution can reach 10 ^-7/ RIU (refractive index unit) is than other intensity modulation type sensor, and resolution can improve two orders of magnitude.

Brief description of the drawings

Fig. 1 is medium magneto-optic surface plasma resonance structural drawing.

Fig. 2 is the change curve of reflectivity with positive negative fluxfield and magnetooptical layer thickness.

Fig. 3 is the change curve of positive negative fluxfield refractive index difference with variations in refractive index and incident angle.

Fig. 4 is the comparison of medium magneto-optic surface plasma resonance and surface plasma resonance.

Fig. 5 is the comparison of medium magneto-optic surface plasma resonance and magneto-optic surface plasma resonance, is the figure of merit of two kinds of different WOSPR and the relation of surface water layer thickness.

Fig. 6 is the field pattern of medium magneto-optic surface plasma resonance.

Fig. 7 is the schematic diagram of duty of the present invention.In figure, 1-prism, 2-silver, 3-CeYIG, 4-analyte coordination body, 5-tracer liquid, 6-detecting device.Arrow express liquid flow direction in tracer liquid, the arrow in prism represents radiation direction.

Embodiment

The present invention proposes the novel sensor based on DMOSPR of prism/silver/CeYIG/ water (or air).The technical scheme adopting is: high index of refraction (2.2), low-loss, the strong magneto-optic effect (2.3 × 10 of utilizing medium magnetooptical layer (CeYIG) ⁴deg/cm, near 1000nm), and utilize silver near 1000nm wavelength, to have low loss, and CeYIG has high magneto-optic effect near 1000nm wavelength, both perfect combination, can further improve device sensitivity.Optimization by emulation to device performance, obtains the wavelength at 1160nm, the thickness 41nm of silver, and CeYIG thickness 25nm place, obtains optimum sensing capabilities, can be able to reach the increase of an order of magnitude than traditional magneto-optic surface plasma device sensitivity.

Compared with prior art, the refractive index that medium magneto-optic memory technique is high can be pushed the pattern of field to dielectric layer, thereby has avoided the loss that metal is high; Low-loss makes surface plasma-wave can propagate farther distance; High magneto-optic effect makes an enhancement effect stronger; Silver has low loss near 1000nm wavelength, and CeYIG has high magneto-optic effect near 1000nm wavelength, and both perfect combination, can further improve device sensitivity.Utilize the supersensitivity of surface plasma-wave effects on surface refraction index changing, survey the variation of reflectivity strength signal.Further, obtain the relation curve of reflectance varies and incident angle according to the difference of added magnetic direction, can realize overdelicate biological and chemical sensor by such signal processing.

Embodiment:

The prism-coupled structure (as shown in Figure 1) of selecting prism/silver/CeYIG/ water, its parameter is as follows: the normal ε of dielectric of prism ₁=2.295, the DIELECTRIC CONSTANT ε of silver ₂=-62.485+4.331i, the permittivity tensor of CeYIG ${\mathrm{\ϵ}}_3=\left[\begin{array}{ccc}5.2-0.0497i& -i*(0.26-0.0098i)& 0\\ i*(0.26-0.0098i)& 5.2-0.0497i& 0\\ 0& 0& 5.2-0.0497i\end{array}\right],$ The DIELECTRIC CONSTANT ε of water ₄=1.7689, the thickness d of silver ₁=41nm, the thickness d of CeYIG ₂=25nm, operation wavelength λ=1.16 μ m. r (H ⁺), R (H ^-) be respectively the reflectivity that adds positive negative fluxfield; θ is the angle that light incides prism surface; N is the refractive index of water.Shown in Fig. 2 is to be 25nm and 35nm for CeYIG thickness, the curve that the magnetic direction of change CeYIG layer obtains, and changing magnetic direction reflectivity curve has very little movement, and due to 35nm thickness C, eYIG has stronger magneto-optic effect, so movement is larger.Signal to sensing is further processed, deduct negative fluxfield reflectivity with positive flux field reflectivity, obtain a more precipitous transducing signal curve, as shown in Figure 3, the refractive index that Fig. 3 has showed CeYIG25nm and 35nm thickness water is changed into 1.34 positive negative fluxfield reflection differences and the relation curve of angle by 1.33.The minimum change that can detect refractive index by angular-sensitive sensor reaches 10 ^-7.At 1160nm wavelength, silver-colored 41nm is thick, the thick place of CeYIG25nm, and obtaining the best figure of merit is 8.355.As shown in Figure 4, because magnetic field strengthens SPR surface field, than traditional spr sensor that there is no magnetooptical layer, its angle sensor improves.Compare conventional iron magnetosphere magneto-optic plasma resonance device, there is the raising of nearly two orders of magnitude (because gold/cobalt/gold is the value obtaining in the wavelength emulation of 632nm, as also increased to some extent in its figure of merit of 1160nm wavelength, but due to the low loss of medium magnetooptical layer, its figure of merit has the raising of an order of magnitude at least), as shown in Figure 5.The sectional drawing of the realistic model in the Comsol of Tu6Shi simulation software and mould field distribution situation.Fig. 7 has showed working environment of the present invention.Prism of the present invention just plays ripple and loses the effect of compensation, and generally using refractive index is the prism of 1.515 BK27 material, and shape is not limit, but semicircle cylindricality is preferably convenient to adjusting angle.

Claims (2)

1. the high sensitivity index sensor based on medium magneto-optic surface plasma resonance, is characterized in that, is provided with silver layer at the reflecting surface of prism, is provided with CeYIG layer on silver layer.

2. the high sensitivity index sensor based on medium magneto-optic surface plasma resonance as claimed in claim 1, is characterized in that, silver thickness is 41nm, and CeYIG layer thickness is 25nm.