| Raman spectroscopy technology has been applied to substance detection for many years,during which time Raman spectroscopy technology has made considerable progress.Produced a variety of Raman spectroscopy technologies,among which the emerging CARS microscopic imaging technology have been in the fields of biological and medical imaging.Coherent anti-Stokes Raman scattering(CARS)microscopy is a recently developed nonlinear vibrational imaging technique for high-sensitivity,three-dimensional,and chemically selective imaging without exogenous labeling agents of lipids,especially lipids in live cells an organisms.In order to further enhance the sensitivity of CARS microscopy,it is very important to provide a plasmon-enhanced substrate with high enhancement and good stability.this paper analyzes the enhancement principle of SECARS and the resonance characteristics of SPR and briefly introduces numerical calculation methods that can analyze various complex structures.There are various designs of existing SECARS substrates,including various shapes of nano metal particles.From simple multimers to complex spatial distribution structures,each substrate is optimized in a certain direction and poses new challenges.At the same time,after experimenting with these substrates,the scientists also pointed out the difficulties in the application of the SECARS substrate.The theoretical value is greatly reduced due to the existence of multiple interference factors in the actual situation.New challenges are proposed for the application of SECARS substrate.With the improvement of synthesis technology,further analysis and understanding of the interference factors in the experiment,the new substrate can already achieve the theoretically expected results.Then analyze the various existing plasmon-enhanced substrates and summarize their advantages and disadvantages.In this work we theoretically designed a new linked nanosystems SECARS substrate that Fano resonance can be generated by the plasmon hybridization(PH)model resonance and the charge transfer plasmon(CTP)resonance.The introduction of charge transfer plasma improves the tunability of structural resonance.By adjusting the conductivity of the conductive junction,the wavelength of the charge transfer plasma resonance can be easily adjusted to change the wavelength position of the Fano resonance.The data obtained by numerical simulation of the Raman mode at 1557cm-1 of Ltryptophan when using a 1064 nm light source as the pump light shows that this spatially symmetrical structure can generate multiple high-enhancement hot spots that do not depend on the polarization direction of the incident light.Ordinary CARS signal can generally be enhanced by 1012,and the maximum can reach 1014.This method of using charge transfer plasma to design a substrate can be applied in the practical substrate of SECARS and provide new ideas for the design of other nonlinear optical processes such as four wave mixing and stimulated Raman scattering. |
