Four-dimensional light shaping: manipulating ultrafast spatiotemporal foci in space and time

Abstract

The spectral dispersion of ultrashort pulses allows the simultaneous focusing of light in both space and time, which creates so-called spatiotemporal foci. Such space–time coupling may be combined with the existing holographic techniques to give a further dimension of control when generating focal light fields. In the present study, it is shown that a phase-only hologram placed in the pupil plane of an objective and illuminated by a spatially chirped ultrashort pulse can be used to generate three-dimensional arrays of spatio-temporally focused spots. By exploiting the pulse front tilt generated at focus when applying simultaneous spatial and temporal focusing (SSTF), it is possible to overlap neighboring foci in time to create a smooth intensity distribution. The resulting light field displays a high level of axial confinement, with experimental demonstrations given through two-photon microscopy and the non-linear laser fabrication of glass.

Multiplexed temporally focused light shaping for high-resolution multi-cell targeting

“…The main concept behind it is to decouple the light shaping into two completely independent steps: a first beam-shaping unit generates and focuses a desired 2D shape on the TF grating; in a second step a SLM, placed after the grating, axially and laterally multiplexes the 2D shape creating a 3D distribution of an arbitrary number of replicas. A similar multiplexing scheme was recently 20 used to replicate GPC shapes in 1P regime 50 , or temporally focused low-NA Gaussian beams 51 . In the former case, the lack of 2PE and TF limited the achievable axial resolution, whereas in the latter the method was restricted to the generation of a static and single-size Gaussian spot.…”

A Miniature Fibre-Optic Raman Probe Fabricated by Ultrafast Laser-Assisted Etching

“…When optimal irradiation parameters are used, the laser-induced modification enhances the local etchability of the silica by up to three orders of magnitude [15,16], allowing the laser-inscribed material to be subsequently removed in a second, chemical etching step. Within the last two decades, collaborative efforts towards better understanding the light-matter interactions [17][18][19] and chemical etching mechanisms [20] and advanced writing techniques [21,22] have established ULAE as a capable manufacturing method for complex glass microcomponents and systems [23,24]. Recently, ULAE has shifted away from using the widely adopted but notoriously hazardous etching agent hydrofluoric acid (HF) to potassium hydroxide (KOH), making the technique much more appealing for industry-level manufacturing.…”

Multiplexed temporally focused light shaping through a GRIN lens for precise in-depth optogenetic photostimulation

“…This was done either by generating multiple diffraction-limited spots that were scanned simultaneously across multiple cell somata [18][19][20] , or by using computer generate holography (CGH) to produce light patterns covering multiple cell somata at once 21 , thus optimizing the temporal precision of the photostimulation 22 . Recently, several research groups [23][24][25][26][27] have shown that using a two-step wave front shaping combined with temporal focusing (TF) [28][29][30][31] it is possible to generate multiple high resolution extended light patterns in 3D, a technique we named multiplexed temporally focused light shaping (MTF-LS). These approaches led to the first demonstrations of neural circuit manipulation in 3D 25,26 , yet the need of using conventional high numerical aperture (NA) objectives limited their use to circuits in superficial (≤ 300 µm) cortical areas or to in-vitro applications.…”