An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

Abstract

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10(17) W cm(-2)) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

Laser produced electromagnetic pulses: generation, detection and mitigation

“…An effective way to minimize this emission is to have no physical connection between the target and the vacuum chamber. Here, we describe experiments performed at Imperial College (UK) with levitating targets, which were sustained without the use of any physical holder, reporting also on the related reduction of EMP emission [159] . lines -results of simulations with ChoCoLaT2 code [36] .…”

Strong electromagnetic pulses generated in high-intensity short-pulse laser interactions with thin foil targets

“…However, a complete quantitative understanding of this phenomenon is still lacking. The EMP effect continues to attract considerable attention and is now being investigated also with the use of smaller laser facilities (Aspiotis et al, 2006;Miragliotta et al, 2011; Consoli et al, 2013;Dubois et al, 2014;De Marco et al, 2014;Cikhardt et al, 2014;Varma et al, 2014; Poyé et al, 2015a; Poyé et al, 2015b;Price et al, 2015; Consoli et al, 2015aConsoli et al, , 2015b Consoli et al, , 2016 De Marco et al, 2016, 2017Yi et al, 2016;Robinson et al, 2017;Krása et al, 2017a). In particular, a series of recent articles (Dubois et al, 2014; Poyé et al, 2015a; Poyé et al, 2015b) concentrated on the effect of electromagnetic emission related to the target neutralization current, which is of pulsed nature and which appears as a consequence of the laser-induced electric polarization of the target (Pearlman & Dahlbacka, 1977;Benjamin et al, 1979;Beg et al, 2004;Quinn et al, 2009;Krása et al, 2015;Krása et al, 2017b).…”

Effects of acoustic levitation on the development of zebrafish, Danio rerio, embryos

“…In addition to AL, there are other levitation techniques that rely on physical fields such as light 32 , electrostatic 33 and magnetic 34 fields. Common to all levitation techniques is the goal to trap matter in vacuum, gas or liquid without touching the sample to provide resemblance of a micro-gravity environment.…”