High stability white light generation in water at multi-kilohertz repetition rate

TL;DR

This paper demonstrates a highly stable, broad supercontinuum light source in water at multi-kilohertz repetition rates by controlling thermal effects with a laminar flow, achieving wider spectral coverage than traditional materials.

Contribution

It introduces a novel fluid flow control method to stabilize supercontinuum generation in water at high repetition rates, enabling wider spectral bandwidths compared to established materials.

Findings

Supercontinuum spans over one octave from VIS to NIR.

Spectral bandwidth increased by 60% over YAG and 40% over sapphire.

Stable operation achieved at 50 kHz and 100 kHz repetition rates.

Abstract

Efficient supercontinuum (SC) generation featuring high spectral intensity across a large bandwidth requires high peak powers of several megawatt from pulsed lasers. Under these conditions and at multi-kilohertz (kHz) repetition rates, the SC generated in most materials is unstable due to thermal effects. In this work, we leverage the superior dispersion properties of water to maximize the spectral width of the SC, while avoiding stability issues due to thermal loading by means of a constant laminar flow of the liquid. This flow is controlled by a differential pressure scheme that allows to precisely adjust the fluid velocity to an optimum value for maximum stability of the SC. This approach is successfully implemented for repetition rates of 50 kHz and 100 kHz and two different pump wavelengths in the visible (VIS) and near infrared (NIR) spectral region with stability of the SC signal only limited by the driving pulses. The resulting water SC spans more than one octave covering the VIS to NIR range. Compared to established materials, such as yttrium aluminum garnet (YAG) and sapphire, the spectral bandwidth is increased by 60 % and 40 % respectively. Our scheme has the potential to be implemented with other liquids such as bromine or carbon disulfide (CS2), which promise even wider broadening and operation up to the mid-infrared.