Localized surface plasmon resonance sensing system with particles arranged in anisotropic periodic manner

Abstract

A localized surface plasmon resonance (LSPR) sensing system with particles arranged in anisotropic periodic manner is revealed. The anisotropy of the nanoparticle array spectrally splits the phase spectra of two perpendicular polarizations thus inducing a phase difference between the two polarizations. An apparatus of ellipsometry is used to measure the phase difference. The simulated results demonstrate that the full width at the half maximum of the spectrum of phase difference is much narrower than the spectrum of transmittance. Therefore the figure of merit is dramatically increased and the performance of the refractive index sensor is improved

What is claimed is: 
     
         1 . A localized surface plasmon resonance (LSPR) sensing system with metal particles arranged in an anisotropic periodic manner that generates a phase signal of LSPR by metal nanoparticles arranged in an anisotropic periodic manner comprising:
 a light source that generates an incident light;   a polarizer that polarizes the incident light;   a test specimen that includes a metal nanoparticle layer having a plurality of metal nanoparticles in a periodical arrangement thereon; the periodic arrangement doesn't have 4-fold rotational symmetry; the metal nanoparticle layer is in contact with a test sample and is excited by the incident light to generate phase signals of the LSPR;   an analyzer that filters out polarization state of an emergent light from the test specimen;   a monochromator arranged at a light path of the LSPR sensing system and used to resolve spectral information; and   an optical detection system that receives the emergent light from the test specimen and detects spectrum of a phase signal of the emergent light.   
     
     
         2 . The system as claimed in  claim 1 , wherein the incident light is not a monochromatic light. 
     
     
         3 . The system as claimed in  claim 1 , wherein the emergent light from the test specimen is transmitted light or reflected light. 
     
     
         4 . The system as claimed in  claim 1 , wherein the emergent light from the test specimen is a superposition of two orthogonal polarization states; the phase signal of the emergent light detected by the optical detection system is a difference between phases of the two orthogonal polarizations. 
     
     
         5 . The system as claimed in  claim 1 , wherein an interrogated information of the LSPR system is a spectral shift of the phase signal indicated as wavelength change, frequency change or photon energy change. 
     
     
         6 . The system as claimed in  claim 1 , wherein the metal is selected from the group consisting of gold, silver, copper, aluminum, palladium, platinum, tin, and white gold. 
     
     
         7 . The system as claimed in  claim 1 , wherein the metal nanoparticle in a shape having 4-fold rotational symmetry (90 degrees). 
     
     
         8 . The system as claimed in  claim 1 , wherein the metal nanoparticle is in a shape not having 4-fold rotational symmetry (90 degrees). 
     
     
         9 . The system as claimed in  claim 8 , wherein the two perpendicular axes of the metal nanoparticle meet a requirement of: 1>a length of a short axis/a length of a long axis>0.8. 
     
     
         10 . The system as claimed in  claim 9 , wherein a shape of the metal nanoparticle is a rectangle, a circle or an ellipse.