Analysis of Subcycle Electro-Optic Sampling Without Background

Abstract We explore background-free options to detect mid-infrared (MIR) electric transients. The MIR field and a near-infrared probe interact via sum- (SFG) difference-frequency generation (DFG) in an electro-optic crystal. An intuitive picture based on phasor representation rigorous numerical calculations are used for analysis. It turns out that separating photons generated either by SFG or DFG from the local oscillator spectral filtering leads signal purely proportional intensity envelope. Background-free phase information may be extracted window containing both components blocking background its orthogonal polarization. This variant square of amplitude. is limited finite efficiency polarization filtering. Hilbert transform as conjugate variable time domain play fundamental role context discussed this paper.