Nanosecond illumination source for speckle-free liquid crystalmicroscopy. Issue 4 (16th March 2021)

• Record Type: Journal Article
• Authors: Ryzhkova, A. V.; Jagodič, U.; Muševič, Igor
• Is Part Of: Liquid crystals. Volume 48:Issue 4(2021)
• Page Start: 491
• Page End: 510
• Publication Date: 2021-03-16
• Subjects: Nanosecond illumination -- liquid crystals -- speckle-free illumination -- Kibble-Zurek mechanism; Liquid crystals -- Periodicals; 548.905
• DOI: 10.1080/02678292.2020.1790049
• Languages: English
• ISSNs: 0267-8292

Abstract

ABSTRACT: We present a setup for the speckle-free, low-light microscopy imaging at ~5 ns exposure times. The design is based on stroboscopic principle and uses fast and incoherent fluorescent emission from a dye, excited by a picosecond laser pulse. The basic spatial, spectral, and temporal beam properties are characterised, modelled and compared for two different designs of the source: (i) Rhodamine 6 G dye dissolved in ethanol and put in a glass cuvette, and (ii) random laser based on the dispersion of 300 nm TiO2 nanospheres in an ethanol solution of Rhodamine 6 G dye. The proposed solution of Rhodamine 6 G dye in ethanol put in a glass cuvette gives an excellent image quality with high contrast, excellent stability and tunable coherence. It delivers ~30 nJ of completely incoherent light per excitation laser pulse energy of ~40 μ J. It allows for the photographic measurements with 5 ns exposure time, demonstrated in imaging of thermally quenched 5CB liquid crystal. The set-up is used in studies of Kibble-Zurek mechanism of topological defect nucleation and growth at sub-microsecond time resolution and extremely fast cooling rates of ~40, 000 K/s. GRAPHICAL ABSTRACT: