Complete characterization of weak, ultrashort near-UV pulses by spectral interferometry

TL;DR

This paper introduces a linear, simple, and sensitive spectral interferometry method for complete characterization of femtosecond near-UV pulses using second harmonic reference and spectral interference, effective over broad spectral ranges.

Contribution

The paper presents a novel spectral interferometry technique for ultrashort UV pulse characterization that is linear, simple, and capable of measuring broad spectral phase features.

Findings

Accurately measures phase over broad spectral range

Detects pi leaps in spectral phase

Effective down to 0.1% spectral intensity

Abstract

We present a method for a complete characterization of a femtosecond ultraviolet pulse when a fundamental near-infrared beam is also available. Our approach relies on generation of second harmonic from the pre-characterized fundamental, which serves as a reference against which an unknown pulse is measured using spectral interference (SI). The characterization apparatus is a modified second harmonic frequency resolved optical gating setup which additionally allows for taking SI spectrum. The presented method is linear in the unknown field, simple and sensitive. We checked its accuracy using test pulses generated in a thick nonlinear crystal, demonstrating the ability to measure the phase in a broad spectral range, down to 0.1% peak spectral intensity as well as retrieving pi leaps in the spectral phase.