Circularly polarized fluorescence from chiral nematic liquid crystalline films: theory and experiment

Abstract

A theory was formulated for the description of circularly polarized¯uorescence (CPF) from a chiral nematic ® lm in the spectral region outside the selective re¯ection band. The CPF theory incorporates: (1 ) the ability of a chiral nematic ® lm to accomplish both circular dichroism and circular polarization and ( 2) linearly polarized¯uorescence from chromophores unaxially aligned in the nematic sublayers comprising the ® lm. Chiral nematic¯uid ® lms consisting of a nematic¯uid, BDH 18523, and a chiral dopant, cholesteryl oleate, were prepared for hosting 1,6-diphenylhexatriene as a¯uorescent dye. The experimentally determined dissymmetry factor using both left-and right-handed circularly polarized excitations was found to be in good agreement with the theoretical prediction with all the system parameters determined a priori. The theory was also employed to furnish insight into the e ects of the concentration of the¯uorescent dye and chiral nematic ® lm thickness on the dissymmetry factor.

Polyfluorene Homopolymers: Conjugated Liquid-Crystalline Polymers for Bright Blue Emission and Polarized Electroluminescence

“…The following mechanism has been proposed and supported by numerical simulations. [91,92] In each nematic sublayer of the film the lumophores are aligned preferentially parallel to the nematic director. Thus, the light emitted locally by each layer is linearly polarized.…”

Highly Ordered Organic Alq3 Chiral Luminescent Thin Films Fabricated by Glancing‐Angle Deposition

“…In practice, g e is limited by the isotropic distribution of luminescent centers throughout the thickness of the film. The best published values of g e for dye-doped chiral nematic liquid crystals are as high as 1.8, according to research by Chen et al [27] and Woon et al [28] In earlier reported results for dye-doped chiral nematic liquid crystals, [29] the reported dissymmetry factor was on the order of 0.8 for an 11 lm thick film. Our preliminary organic, luminescent, porous chiral films show substantial promise, with the 9.25 turn film achieving a peak dissymmetry factor of 0.30 at a wavelength of 524 nm, and the 5.5 turn film achieving a peak dissymmetry factor of 0.20 at 590 nm, particularly compared to inorganic luminescent chiral films of Y 2 O 3 :Eu, which yielded a maximum g e value of 0.10 for a 5 turn film.…”

Organic photonic bandgap microcavities doped with semiconductor nanocrystals for room-temperature on-demand single-photon sources

“…(3) Fiber-optical spectrometer (Ocean Optics). The method of defining the dissymmetry of circular polarization is described in [25]. For circularpolarization measurements both an achromatic quarter waveplate and a Glan Thompson linear polarizer on rotating mounts are placed in the spectrometer port in front of the spectrometer.…”

“…The spectral transmission of the cavity is presented in Figure 2(a). The degree of circular polarization is measured by the dissymmetry factor g e [25,33]:…”