iLIF: illumination by Laser-Induced Fluorescence for single flash imaging on a nanoseconds timescale

Abstract

The challenge in visualizing fast microscale fluid motion phenomena is to record high-quality images free of motion-blur. Here, we present an illumination technique based on laser-induced fluorescence which delivers high-intensity light pulses of 7 ns. The light source consists of a Q-switched Nd:YAG laser and a laser dye solution incorporated into a total internal reflection lens, resulting in a uni-directional light beam with a millimetersized circular aperture and 3°divergence. The laser coherence, considered undesirable for imaging purposes, is reduced while maintaining a nanoseconds pulse duration. The properties of the illumination by laser-induced fluorescence (iLIF) are quantified, and a comparison is made with other high-intensity pulsed and continuous light sources.

High-efficiency ballistic electrostatic generator using microdroplets

“…The jet breaks up into a stream of droplets by the Rayleigh-Plateau instability (Fig. 1c) [15][16][17] . The droplets carry a net positive ionic charge.…”

High-speed imaging in fluids

“…Evidently, the actual temporal resolution τ will be the shortest of both durations, hence τ = min(τp, τc). If we now define ǫ as being the displacement in pixels of the object moving with velocity The motion artifact is reduced by a 7-ns illumination with a laser-induced fluorescence pulse using iLIF [54].…”

“…2.4. A short flash was created by exciting a laser dye solution with a pulsed laser [66,54]. The resulting fluorescent light has a very high intensity, while the undesired coherence of the laser light, which would lead to interference and speckle, is removed.…”

“…It indicates how fast these waves propagate at the small scale. If we were to visualize directly the propagation of such a shockwave, we could resort to stroboscopic laser or iLIF illumination [54] at fixed time delays (see Sect. 3.2) if the propagation of the pressure wave is reproducible.…”

Ultra-high-speed fluorescence imaging

“…This has led to the discovery of several new phenomena, such as "compression-only" behavior [2], shell buckling [19], and shape oscillations [3]. In other fields of research, highspeed optical imaging has also become an valuable tool to accurately determine the position and size of microscopic objects, such as droplets in piezo inkjet printing [35], microjets generated by vapor bubbles [36] and microbubbles for semiconductor surface cleaning [26].…”