Effects of scatterers' sizes on near-field coherent anti-Stokes Raman scattering under tightly focused radially and linearly polarized light excitation.
We employ the finite-difference time-domain (FDTD) technique as a numerical approach to studying the effects of scatterers' sizes on near-field coherent anti-Stokes Raman scattering (CARS) microscopy under tightly focused radially and linearly polarized light excitations. The FDTD results show that in a uniform medium (water), the full width at half maximum (FWHM) (transverse resolution) of radially polarized near-field CARS (RP-CARS) radiation is approximately 7.7% narrower than that of linearly polarized near-field CARS (LP-CARS) imaging, whereas the depth of focus (DOF) of RP-CARS radiation is 6.5% longer than LP-CARS. However, with the presence of scatterers in the uniform medium, both the FHWM and DOF of near-field RP-CARS radiation become much narrower compared to those of near-field LP-CARS radiation. In addition, the signal to nonresonant background ratio of near-field RP-CARS is significantly improved when the scatterer's size is larger than a half wavelength of the pump light field. This work suggests that near-field CARS radiations are strongly influenced by the scatterers' sizes in the medium; and near-field RP-CARS microscopy is superior to the near-field LP-CARS by providing both higher transverse and axial resolutions for three-dimensional molecular imaging of fine structures in biological systems.
Lin
Jian
J
Bioimaging Laboratory, Department of Bioengineering, Faculty of Engineering, National University of Singapore, Singapore 117576, Singapore.
Zheng
Wei
W
Wang
Haifeng
H
Huang
Zhiwei
Z
D003198:Computer Simulation; D008027:Light; D016014:Linear Models; D008962:Models, Theoretical; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D012031:Refractometry / Q000379:methods*; D012542:Scattering, Radiation; D013059:Spectrum Analysis, Raman / Q000379:methods*; D020349:Surface Plasmon Resonance / Q000379:methods*