Distinguishing Resonant from Non-Resonant Nonlinear Optical Processes Using Intensity-Intensity Correlation Analyses

Area of Science:

• Spectroscopy
• Chemical analysis
• Laser-induced phenomena

Background:

• Coherent anti-Stokes Raman scattering (CARS) involves complex resonant and non-resonant processes.
• Understanding the progressive buildup of resonant CARS signals is crucial for advanced analysis.
• Existing analytical tools may not fully capture the dynamics of deferred resonant signal buildup.

Purpose of the Study:

• To develop and adapt quantitative analytical tools for analyzing CARS signal dynamics.
• To investigate the phenomenon of deferred resonant signal buildup in CARS.
• To enhance the analytical capabilities for distinguishing resonant and non-resonant processes.

Main Methods:

• Introduction of one-dimensional and two-dimensional intensity-intensity correlation functions.
• Utilizing probe pulse delay and probe pulse linewidth as key variables and perturbation parameters.
• Definition of discrete diagonal directional sums to simplify two-dimensional correlation spectroscopy (2D-COS) maps.

Main Results:

• Demonstration of a novel analytical approach for CARS signal analysis.
• Successful reduction of complex 2D-COS maps to informative 1D plots.
• Validation using all-Gaussian CARS closed-form solutions and experimental data for resonant and non-resonant scenarios.

Conclusions:

• The developed correlation analyses effectively reveal deferred resonant signal buildup in CARS.
• The methodology provides a powerful tool for distinguishing between resonant and non-resonant chemical species.
• Potential industrial applications include differentiating hydrocarbons from water in extractive industries.