title: Image formation in CARS microscopy: effect of the Gouy phase shift.
abstract: Image formation in Coherent Anti-Stokes Raman Scattering (CARS) microscopy of sub-wavelength objects is investigated via a combined experimental, numerical and theoretical study. We consider a resonant spherical object in the presence of a nonresonant background, using tightly focused laser pulses. When the object is translated along the laser propagation axis, we find the CARS signal to be asymmetric about the laser focal plane. When the object is located before the focus, there is a distinct shadow within the image, whereas the brightest signal is obtained when the object is behind the focus. This behaviour is caused by interference between resonant and nonresonant signals, and the Gouy phase shift is responsible for the observed asymmetry within the image.
authors: Department of Physics, University of Ottawa, Ottawa, Ontario, Canada.
authors: K I
authors: KI
authors: Popov
authors: A F
authors: AF
authors: Pegoraro
authors: A
authors: A
authors: Stolow
authors: L
authors: L
authors: Ramunno
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008853:Microscopy / Q000295:instrumentation* / Q000379:methods*; D008962:Models, Theoretical; D013059:Spectrum Analysis, Raman / Q000295:instrumentation* / Q000379:methods*