ABSTRACT
Coherent anti-Stokes Raman scattering (CARS) interferometry is used to deplete the anti-Stokes radiation emerging from a tightly focused spot. Near-to-complete depletion of the anti-Stokes radiation is obtained when a phase-controlled local oscillator field at the anti-Stokes frequency is out of phase with the induced CARS field in the focal volume. Unlike in traditional interferometry, this depleted energy is not spatially redistributed. A theoretical analysis shows that the energy loss in the anti-Stokes channel is accompanied by an energy gain in the pump and Stokes channels. Interferometric switching of anti-Stokes radiation may offer a route toward developing high-resolution CARS microscopy.
ABSTRACT
The coherent anti-Stokes Raman scattering (CARS) signal is calculated as a function of focal-field distributions with engineered phase jumps. We show that the focal fields in CARS microscopy can be shaped such that the signal from the bulk is suppressed in the forward detection mode. We present the field distributions that display enhanced sensitivity to vibrationally resonant object interfaces in the lateral dimension. The use of focus-engineered CARS provides a simple means to detect chemical edges against the strong background signals from the bulk.
Subject(s)
Algorithms , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Microscopy/methods , Models, Biological , Spectrum Analysis, Raman/methods , Tomography, Optical Coherence/methods , Computer Simulation , Image Enhancement/instrumentation , Image Interpretation, Computer-Assisted/instrumentation , Microscopy/instrumentation , Numerical Analysis, Computer-Assisted , Spectrum Analysis, Raman/instrumentation , Tomography, Optical Coherence/instrumentationABSTRACT
We report a simple and robust computer-based active interferometer stabilization scheme which does not require modulation of the interfering beams and relies on an error signal which is linearly related to the optical path difference. In this setup, a non-collinearly propagating reference laser beam stabilizes the interference output of the laser light propagating collinearly through the interferometer. This stabilization scheme enables adjustable phase control with 20 ms switching times in the range from 0.02pi radians to 6pi radians at 632.8 nm.
