Single-frame characterization of ultrafast pulses with spatiotemporal orbital angular momentum

TL;DR

This paper introduces a simple, single-frame, spatially resolved spectral interferometry method for rapid, quantitative characterization of ultrafast pulses carrying spatiotemporal orbital angular momentum, enabling quick feedback and high-throughput analysis.

Contribution

The authors develop a novel, straightforward technique for single-frame measurement of ultrashort ST-OAM pulses, capturing key characteristics without complex data analysis.

Findings

Successfully identified ST-OAM pulse features such as topological charge and OAM helicity from raw data.

Fully characterized pulse dispersion and beam divergence after processing.

Method enables high-speed, potentially single-shot, pulse measurement.

Abstract

Light carrying spatiotemporal orbital angular momentum (ST-OAM) makes possible new types of optical vortices arising from transverse OAM. ST-OAM pulses exhibit novel properties during propagation, transmission, refraction, diffraction, and nonlinear conversion, attracting growing experimental and theoretical interest and studies. However, one major challenge is the lack of a simple and straightforward method for characterizing ultrafast ST-OAM pulses. Using spatially resolved spectral interferometry, we demonstrate a simple, stationary, single-frame method to quantitatively characterize ultrashort light pulses carrying ST-OAM. Using our method, the presence of an ST-OAM pulse, including its main characteristics such as topological charge numbers and OAM helicity, can be identified easily from the unique and unambiguous features directly seen on the raw data--without any need for a full analysis of the data. After processing and reconstructions, other exquisite features, including pulse dispersion and beam divergence, can also be fully characterized. Our fast characterization method allows high-throughput and quick feedback during the generation and optical alignment processes of ST-OAM pulses. It is straightforward to extend our method to single-shot measurement by using a high-speed camera that matches the pulse repetition rate. This new method can help advance the field of spatially and temporally structured light and its applications in advanced metrologies.