Simultaneous spatial and temporal focusing of femtosecond pulses

Abstract

We study and demonstrate the technique of simultaneous spatial and temporal focusing of femtosecond pulses, with the aim to improve the signal-to-background ratio in multiphoton imaging. This concept is realized by spatially separating spectral components of pulses into a "rainbow beam" and recombining these components only at the spatial focus of the objective lens. Thus, temporal pulse width becomes a function of distance, with the shortest pulse width confined to the spatial focus. We developed analytical expressions to describe this method and experimentally demonstrated the feasibility. The concept of simultaneous spatial and temporal focusing of femtosecond pulses has the great potential to significantly reduce the background excitation in multiphoton microscopy, which fundamentally limits the imaging depth in highly scattering biological specimens.

Diagnostics and controls for spatiotemporal couplings for laser-plasma accelerator drivers

“…Spatiotemporal couplings exhibit dynamic behavior near focus, the relevant location for laser-plasma interaction; therefore, simulations of pulses at the vicinity of focus based on the measurement at near-field are important. There are several methods to calculate pulse propagation with spatiotemporal couplings [17,24], and plane wave decomposition was used in this work.…”

All-optical quantum storage based on spatial chirp of the control field

“…Optical fields with a spatial chirp across the beam have been widely used in Fourier synthesis pulse shaping [43], multiphoton microscopy [44,45], micromachining [46], etc., and have also been proposed to assist the achievement of large EIT bandwidth by applying a magnetic field transverse gradient [47]. They commonly exist in the inhomogeneous dispersive medium, and can be produced by means of prism or grating diffraction [48], pulse spatial modulation [49], etc..…”

Monte Carlo Simulation of Image Depth Improvement by Two-color Two-photon Fluorescence Microscopy

“…8,9) In this technique, the spectral components of the femtosecond laser pulse are first separated in space for stretching the pulse, and then they will become completely overlap again at the focus for reproducing the shortest pulse duration. Therefore, the relatively long pulse durations in the out-of-focus areas can help suppress the background excitation, leading to improved signal-background ratio (SBR).…”