Phase matching in two-dimensional coherent Raman imaging.

Area of Science:

• Spectroscopy
• Chemical Physics
• Fluid Dynamics

Background:

• Coherent Anti-Stokes Raman Scattering (CARS) is crucial for temperature and species concentration measurements, particularly in reacting flows.
• Multi-dimensional CARS, especially 2-D CARS imaging, requires specific phase-matching schemes for effective implementation.
• Traditional collinear and BOXCARS schemes achieve broad spectral range, but 2-D imaging necessitates two-beam or counter-propagating arrangements.

Purpose of the Study:

• To investigate the performance of different phase-matching schemes in two-dimensional CARS (2-D CARS) imaging.
• To quantify the trade-offs between spatial resolution, spectral bandwidth, and CARS signal intensity in various 2-D CARS configurations.
• To provide insights into optimizing 2-D CARS arrangements for reacting flow diagnostics.

Main Methods:

• Theoretical calculations and simulations were performed for two-beam and counter-propagating beam CARS arrangements.
• Analysis focused on the impact of phase-matching schemes on key performance metrics.
• The study evaluated spectral response limitations introduced by the two-beam arrangement.

Main Results:

• The two-beam CARS arrangement, while advantageous, introduces phase mismatch that restricts spectral response.
• Trade-offs exist between spatial resolution, spectral bandwidth, and CARS intensity depending on the chosen phase-matching scheme.
• Calculations provide quantitative data on these trade-offs for both two-beam and counter-propagating configurations.

Conclusions:

• Understanding phase-matching scheme trade-offs is critical for optimizing 2-D CARS measurements.
• The choice of arrangement significantly impacts the quality and scope of data obtained in 2-D CARS imaging.
• This research aids in selecting appropriate CARS configurations for advanced diagnostics in complex environments like reacting flows.