Suppression of coherent interference to electric-field-induced second-harmonic (E-FISH) signals for the measurement of electric field in mesoscale confined geometries

We present spatially enhanced electric-field-induced second -harmonic (SEEFISH) generation with a chirped femtosecond beam for measurements of electric field in mesoscale confined geometries subject to destructive spurious second-harmonic generation (SHG). Spurious SHG is shown to interfere with the measured E-FISH signal coherently, and thus simple background subtraction is not sufficient for single-beam E-FISH approaches, especially in a confined system with a large surface-to-volume ratio. The results show that a chirped femtosecond beam is effective in preventing higher-order mixing and white light generation in windows near the beam focal point which further contaminates the SEEFISH signal. The successful measurements of electric field of a nanosecond dielectric barrier discharge in a test cell demonstrated that spurious SHG detected with a con-gruent traditional E-FISH approach can be eliminated using the SEEFISH approach. (c) 2023 Optica Publishing Group

Automated summary

We propose a spatially enhanced electric-field-induced second-harmonic (SEEFISH) generation method using a chirped femtosecond beam to measure the electric field in mesoscale confined geometries. The chirped femtosecond beam effectively prevents higher-order mixing and white light generation near the beam focal point, reducing contamination of the SEEFISH signal. Successful measurements of electric field in a nanosecond dielectric barrier discharge demonstrate the effectiveness of the SEEFISH approach in eliminating spurious second-harmonic generation detected by traditional E-FISH methods.