Vortex-comb spectroscopy

TL;DR

Vortex-comb spectroscopy introduces a novel Fourier-transform method utilizing the rotational Doppler effect, enabling high-resolution, fast, mode-resolved spectral measurements with a single frequency comb and vortex modes.

Contribution

This work presents a new vortex-based Fourier-transform spectroscopy technique that surpasses traditional methods in resolution and speed, using orbital angular momentum modes and rotational Doppler effects.

Findings

Achieved up to eleven OAM modes with a tunable laser and spiral phase plates.

Spectral resolution depends on measurement time, not mechanical scan distance.

Demonstrated fast, mode-resolved spectral measurements with a single frequency comb.

Abstract

We propose a new Fourier-transform spectroscopy technique based on the rotational Doppler effect. The technique offers an application for optical vortex frequency combs, where each frequency component carries a unique amount of orbital angular momentum (OAM). Here, we emulate a vortex comb using a tunable single frequency laser and a collection of spiral phase plates, generating up to eleven distinct OAM modes. Unlike in traditional Fourier-transform spectroscopy based on the Michelson interferometer (linear Doppler effect), the spectral resolution of vortex-comb spectroscopy is not limited by the mechanical scan distance of the instrument but only by the measurement time. Although the spectrometer requires just one free-running frequency comb, the down-conversion scheme resembles dual-comb spectroscopy, leading to fast mode-resolved measurements.