Multiplicative and subtractive focal volume engineering in coherent Raman microscopy.
Rigorous calculations are performed to study the effective reduction of the nonlinear excitation volumes when using phase-only masks to condition the pump and Stokes driving fields. Focal volume reduction was achieved using both a multiplicative operation of the excitation fields as well as a subtractive operation. Using a tunable optical bottle beam for the Stokes field, an effective reduction of the width of the excitation volume by a factor of 1.5 can be achieved in the focal plane. Further reduction of the focal volume introduces a rapid growth of sidelobes, which renders such volumes unsuitable for imaging applications. In addition, phase sensitive detection was found to provide information from selective sub-divisions of the engineered coherent anti-Stokes Raman scattering excitation volume. In the case of isolated nanoparticles, an apparent resolution improvement by a factor of 3 is demonstrated, and it is shown that the size of sub-diffraction-limited particles can be accurately determined using phase sensitive detection.
Department of Chemistry and Beckman Laser Institute, University of California at Irvine, Irvine, California 92697, USA.
Varun
V
Raghunathan
Eric Olaf
EO
Potma
D003116:Color; D004581:Electronics; D008853:Microscopy / Q000379:methods*; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013382:Subtraction Technique