Variable electro-optic shearing interferometry for ultrafast single-photon-level pulse characterization

TL;DR

This paper presents a novel electro-optic shearing interferometry technique for ultrafast pulse characterization at the single-photon level, avoiding nonlinear effects and enabling fully-electronic control for spectral and temporal analysis.

Contribution

It introduces a nonlinear-effect-free, electro-optic method for ultrafast pulse characterization suitable for single-photon-level measurements with full spectral and temporal reconstruction.

Findings

Successfully characterized classical and single-photon pulses

Reconstructed spectral phase and amplitude accurately

Method is compatible with partially-incoherent light

Abstract

Despite the multitude of available methods, the characterisation of ultrafast pulses remains a challenging endeavour, especially at the single-photon level. We introduce a pulse characterisation scheme that maps the magnitude of its short-time Fourier transform. Contrary to many well-known solutions it does not require nonlinear effects and is therefore suitable for single-photon-level measurements. Our method is based on introducing a series of controlled time and frequency shifts, where the latter is performed via an electro-optic modulator allowing a fully-electronic experimental control. We characterized the full spectral and temporal width of a classical and single-photon-level pulse and successfully reconstructed their spectral phase and amplitude. The method can be extended by implementing a phase-sensitive measurement and is naturally well-suited to partially-incoherent light.