Phototunable lasing in dye-doped cholesteric liquid crystals

Abstract

In this letter, we report the results of phototunable lasing in dye-doped cholesteric liquid crystals (DD–CLC). Photoexcitation of DD–CLC films gives rise to laser emission in the violet-UV range. Control of the structure of the chiral dopant driven by UV phototransformation is exploited in order to obtain a permanent variation of the cholesteric pitch. Laser emission wavelength tuning, by means of photoinduced shifting of the selective reflection band of the cholesteric liquid crystals is established. A tuning interval of about 35 nm, in the wavelength range of 385–415 nm, is observed.

Lasing Characteristics of Dye-Doped Cholesteric Liquid Crystal

“…Control of the structure of the chiraldopant driven by UV photo transformation was exploited in order to obtain a permanent variation of the cholesteric pitch. Laser emission wavelength tuning was established with the help of photoinduced shifting of the selective reflection band of the cholesteric liquid crystals [32].…”

Different Approaches of Employing Cholesteric Liquid Crystals in Dye Lasers

“…In first case to the nematic MLC-6816 was doped with a chiral compound ZLI-3786 whose chemical structure is identical to the one of ZLI-811. Like ZLI-811 the mixture NLC + ZLI-3786 undergoes a photo-Fries transformation [30,39] if irradiated at wavelengths shorter than 300 nm. To create a pitch gradient within the CLC layer containing ZLI-3786, distinct regions of the layer have been exposed to UV for different times using a customized mask.…”

“…In [30] was proposed the tuning of the lasing wavelength by light. In this pioneering work the controlling of the generated laser wavelength was carried out by means of phototransformation of a well known chiral dopant from Merck ZLI-811 [left-handed (S-811) and righthanded ZLI-3786 (R-811)] whose light sensitivity was never considered before.…”

Experimental Investigation of Laser Emission of Dye-Doped Cholesteric Liquid Crystals with a Cholesteric Reflector

“…So far, reports have shown that low threshold laser action are readily observed not only in chiral nematic liquid crystal [4,5] but also in ferroelectric liquid crystal (smectic C Ã ) [6], blue phase liquid crystal [7], cholesteric polymer [8,9], cholesteric elastomer [10] and more recently cholesteric glasses [11]. Tunability of lasing in these systems can be achieved by the control of chiral agent concentration, external electrical field [12], temperature [13], mechanical stress [10], and photochemical effect [14,15].…”