Abstract: recently modeled third-order sum-frequency generation (TSFG) in droplets. The basic approach is similar to the model developed by Cooney and Gross for coherent anti-Stokes Raman scattering (CARS) from droplets. In this model, three generating waves interact to generate a third-order nonlinear polarization, which then radiates inside the sphere as described by the model of H. Chew et al. The intensity of the output waves at the sum frequency is proportional to the spatial overlap (amplitude and phase) of the nonlinear polarization with the output resonance of the droplet cavity mode, and to the integral of the products of the frequency dependence of the nonlinear polarization and the output resonance mode. Here we review our approach to modeling TSFG in droplets, discuss second-order sum frequency generation (SSFG) and CARS in droplets, stressing the similarities and differences among TSFG, SSFG, and CARS in droplets, and discuss the possible application of these mixing processes for fuel droplet characterization. We not that TSFG and SSFG from droplets are too weak to be useful for fuel droplet characterization, but that CARS is readily detectable from droplets and may be useful for determining the concentrations of chemical species in fuel droplets.!43
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