Temperature-tunable lasing from dye-doped chiral microdroplets encapsulated in a thin polymeric film

Abstract

In the last decade, much interest has grown around the possibility to use liquid-crystal droplets as optical microcavities and lasers. In particular, 3D laser emission from dye-doped cholesteric liquid crystals confined inside microdroplets paves the way for many applications in the field of sensors or tunable photonics. Several techniques can be used to obtain small microresonators as, for example, dispersing a liquid crystal inside an immiscible isotropic fluid to create an emulsion. Recently, the possibility to obtain a thin free-standing film starting from an emulsion having a mixture of water and polyvinyl alcohol as isotropic matrix has been reported. After the water evaporation, a polymeric film in which the microdroplets are encapsulated has been obtained. Bragg-type laser emission has been recorded from the emulsion as well as from the thin film. Here, we report on the possibility to tune the laser emission as a function of temperature. Using a chiral dopant with temperature dependent solubility, the emitted laser wavelength can be tuned in a range of 40 nm by a temperature variation of 18 °C. The proposed device can have applications in the field of sensors and for the development of anti-counterfeiting labels.

Induced Chiral Chromonics Confined in Micrometric Droplets

“…Further, when cholesteric liquid crystals are used, since the pitch is tunable in the range of visible light and depends on temperature, electric field, pH etc., the control of the director configuration and, hence, of the microspheres optical properties can be used for several applications from display technology to sensors and lasers. [ 10,11 ]…”

Cholesteric Liquid Crystals Based Micro‐Fingerprints Generator for Anti‐Counterfeiting Labels

“…Cholesteric liquid crystals (CLCs) possess several unique properties: 100% selective reflection of one handness of circularly polarized light and the ability to change their selective reflection wavelength changing external or internal factors (electric and electromagnetic fields, temperature, local order). [11][12][13][14][15] Due to their unique properties CNLCs have been used in a plethora of applications in optics, photonics, and security. [16][17][18] In 2012 Nakayama et al have proposed the use of chiral LCs as materials for optical security devices, developing a way to prepare random patterns with a fingerprint-like texture.…”