Laser Pulse Diagnostics of Ultrafast <8 fs Pulses Through Two-Photon Absorption Fluorescence In Liquid Media -- The Role of GVD and Third-Order Dispersion

TL;DR

This paper presents a novel, cost-effective method for characterizing ultrafast sub-8 fs laser pulses using two-photon fluorescence in liquids, accurately determining dispersion parameters and pulse evolution.

Contribution

The study introduces a robust numerical algorithm for pulse characterization via TPA fluorescence, outperforming traditional methods and applicable to non-Gaussian spectral profiles.

Findings

Accurate retrieval of GVD, TOD, and GDD from fluorescence data.

Validation of the method through autocorrelation measurements.

Effective for non-Gaussian spectral intensities.

Abstract

This study investigates the propagation of an ultrafast laser pulse through a liquid medium. A femtosecond laser oscillator with a pulse duration of less than 8 fs is used. By conducting experiments with coumarin and fluorescein dyes in water, methanol, and chloroform, we analyze two-photon absorption (TPA) fluorescence, a method pioneered by Schr\"oder [Opt. Express 14, 10125 (2006)]. A numerical algorithm we developed to model the fluorescence signal determines the group velocity dispersion (GVD), the third-order dispersion (TOD), and the group delay dispersion (GDD). Autocorrelation measurements combined with a detailed analysis confirm the validity of our method and the accuracy of the retrieved temporal profile of the pulse. This cost-effective approach is robust and useful for laser pulse characterization, outperforming traditional methods in terms of alignment sensitivity. Our method allows us to study the time evolution of the pulses as they propagate through the liquid, determines higher-order phase terms as acquired by the pulse while reflecting off the chirped mirrors and propagating through the liquid, and even works for non-Gaussian spectral intensities of the laser.