The time resolved measurement of ultrashort THz-band electric fields without an ultrashort probe

TL;DR

This paper presents a novel method for time-resolved measurement of ultrashort THz electric fields without requiring an ultrashort probe, using nonlinear optical interactions and FROG characterization, which is immune to timing jitter.

Contribution

A new technique for measuring ultrashort THz electric fields without ultrashort probes, utilizing nonlinear spectral transfer and FROG, suitable for non-ultrashort laser generated THz fields.

Findings

Successfully measures THz electric field profiles without ultrashort probes.

Immunity to timing jitter due to narrow-bandwidth optical probe.

Applicable to electron bunch profile measurements in accelerators.

Abstract

The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse, and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.