Doppler-induced continuous spectral broadening of ultraviolet lasers

TL;DR

This paper introduces a novel ultrafast-rotating phase plate scheme that induces Doppler shifts to achieve continuous spectral broadening of ultraviolet lasers, with potential applications in optical frequency combs and inertial fusion.

Contribution

The proposed URPP-based scheme provides a compact, effective method for spectral broadening of UV lasers through Doppler-induced shifts, enhancing laser applications.

Findings

Achieved 0.07% spectral broadening with specific parameters.

Superimposing multiple URPPs enhances broadening and speckle smoothing.

Applicable to optical frequency combs and laser-plasma instability mitigation.

Abstract

We propose a compact scheme based on ultrafast-rotating phase plates (URPPs) to achieve continuous spectral broadening of ultraviolet lasers. The rapid rotation elements behave as a random oscillator which induces Doppler frequency shift into the ultraviolet lasers. As an example, for a disk-shaped phase plate, with the beam acting on the edge at a radius of 10 cm, a rotation frequency of 1 kHz, and a phase-element size of 10 nm, the continuous spectral broadening reaches 0.07%. Further increasing the rotation speed or reducing the phase-element can lead to greater spectral broadening. When multiple URPPs are arranged in series, the superimposed spatiotemporal modulation further enhances the continuous spectral broadening and achieves more effective speckle smoothing. The scheme is applicable to broadening the independent spectrum of optical frequency combs as well as to the mitigation of laser-plasma instabilities in inertial fusion energy.