Magnetic-field tuning of whispering gallery mode lasing from ferromagnetic nematic liquid crystal microdroplets.

Maruša Mur,Vidur Niranjan,Junaid Ahmad Sofi,Igor Muševič,Alenka Mertelj,Surajit Dhara,Darja Lisjak,Ivan Kvasić

doi:10.1364/oe.25.001073

Abstract

We report magnetic field tuning of the structure and Whispering Gallery Mode lasing from ferromagnetic nematic liquid crystal micro-droplets. Microlasers were prepared by dispersing a nematic liquid crystal, containing magnetic nanoparticles and fluorescent dye, in a glycerol-lecithin matrix. The droplets exhibit radial director structure, which shows elastic distortion at a very low external magnetic field. The fluorescent dye doped ferromagnetic nematic droplets show Whispering Gallery Mode lasing, which is tunable by the external magnetic field. The tuning of the WGM lasing modes is linear in magnetic field with a wavelength-shift of the order of 1 nm/100 mT. Depending on the lasing geometry, the WGMs are red- or blue-shifted.

Highlights

Nematic liquid crystals (NLCs) are orientationally ordered liquids of elongated organic molecules, which are spontaneously aligned along a direction, called the director [1]
We report magnetic field tuning of the structure and Whispering Gallery Mode lasing from ferromagnetic nematic liquid crystal micro-droplets
The fluorescent dye doped ferromagnetic nematic droplets show Whispering Gallery Mode lasing, which is tunable by the external magnetic field

Summary

Introduction

Nematic liquid crystals (NLCs) are orientationally ordered liquids of elongated organic molecules, which are spontaneously aligned along a direction, called the director [1] Their optical, dielectric, magnetic and viscoelastic properties are anisotropic [1]. Ferromagnetic nematic liquid crystal exhibits stable domains with ferromagnetic dipole moment, which respond linearly and reorient under very weak magnetic field [10, 11] This discovery created immense interest in the liquid crystal community and subsequently several interesting aspects of these materials were reported [12, 13]. In most of these studies the LCs were confined in between two parallel glass plates, whereas dispersions of ferromagnetic nematic LC in immiscible carrier fluid has remained unexplored. The observed wavelength shifts are linear in the applied magnetic field

Experimental

Results and discussion

Conclusion