Abstract
Coherent anti-Stokes Raman scattering (CARS) and, in particular, femtosecond adaptive spectroscopic techniques (FAST CARS) have been successfully used for molecular spectroscopy and microscopic imaging. Recent progress in ultrafast nano-optics provides flexibility in generation and control of optical near fields, and holds promise to extend CARS techniques to the nanoscale. In this theoretical study, we demonstrate ultrafast subwavelentgh control of coherent Raman spectra of molecules in the vicinity of a plasmonic nanostructure excited by ultrashort laser pulses. The simulated nanostructure design provides localized excitation sources for CARS by focusing incident laser pulses into subwavelength hot spots via two self-similar nanolens antennas connected by a waveguide. Hot-spot-selective dual-tip-enhanced CARS (2TECARS) nanospectra of DNA nucleobases are obtained by simulating optimized pump, Stokes and probe near fields using tips, laser polarization- and pulse-shaping. This technique may be used to explore ultrafast energy and electron transfer dynamics in real space with nanometre resolution.
Highlights
Recent progress in nano-optics has led to many exciting applications that benefit from nanoscale subwavelength resolution, such as imaging cancer cells, biosensing, and designing nanoscale devices [1]
It is desirable to obtain simultaneous nanometre spatial and ultrafast temporal resolution to investigate the dynamics of proteins, surface water, plasmon propagation, energy and charge transfer in biomolecules, and other ultrafast nanoscale processes [2]
In coherent Raman spectroscopy, such as coherent anti-Stokes Raman scattering (CARS) [3,4,5], vibrational coherence is used to enhance molecular signals compared to weak spontaneous Raman spectroscopy
Summary
- Resonant dielectric nanostructures: A lowloss platform for functional nanophotonics Manuel Decker and Isabelle Staude. - Engineering metallic nanostructures for plasmonics and nanophotonics Nathan C Lindquist, Prashant Nagpal, Kevin M McPeak et al. - Roadmap on plasmonics Mark I Stockman, Katrin Kneipp, Sergey I Bozhevolnyi et al
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