Multi-wavelength laser from dye-doped cholesteric polymer films

Huang, Yuhua; Wu, Shin‐Tson

doi:10.1364/oe.18.027697

Cited by 17 publications

(5 citation statements)

References 24 publications

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“…Research on dye loaded polymer films covers different fields of practical interest such as optical chemical sensing, 1 development of laser media, 2 high density optical data storage, 3 security authentication, 4 light trapping for water splitting devices, 5 and singlet molecular oxygen ( 1 O 2 ) photosensitization, 6 among others. For certain applications such as optical storage and photosensitization, small dye-to-dye distances or large absorbances, attainable at high concentrations, are required.…”

Section: Introductionmentioning

confidence: 99%

Tuning the concentration of dye loaded polymer films for maximum photosensitization efficiency: phloxine B in poly(2-hydroxyethyl methacrylate)

Litman

Rodríguez

Román

2016

Photochem Photobiol Sci

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Fluorescence and singlet molecular oxygen ((1)O2) quantum yields for phloxine B loaded poly(2-hydroxyethyl methacrylate) thin films are determined at dye concentrations from 0.015 to 22 wt%. Fluorescence self-quenching and the fall off of the (1)O2 quantum yield observed above 0.1 wt% are attributed to very weakly interacting close-lying dye molecules acting as energy traps arising from molecular confinement. The maximum singlet oxygen generation efficiency (quantum yield × absorption factor) lies at concentrations around 2 wt%, where fluorescence self quenching amounts to more than 80%. Data are fitted quantitatively by using a quenching radius model involving energy migration and trapping with rQ = 1.2 nm. The present results constitute a proof of concept for the rational design of heterogeneous photosensitizers in general and, particularly, for applications in which the antimicrobial activity of singlet oxygen is central.

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Section: Introductionmentioning

confidence: 99%

Tuning the concentration of dye loaded polymer films for maximum photosensitization efficiency: phloxine B in poly(2-hydroxyethyl methacrylate)

Litman

Rodríguez

Román

2016

Photochem Photobiol Sci

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“…This means impossibil ity of observing multimode lasing in the subject system nearby the PBG shortwave border for n 0 e ″ = and n 0 o ″ ≠ , as well as nearby the longwave border for n 0 e ″ ≠ and n 0 o ″ = . And, as it is well known, (see, for instance, [50]), invest igations of possibilities for observing of multimode lasing are of great interest.…”

Section: Resultsmentioning

confidence: 99%

Absorption and emission in defective cholesteric liquid crystal cells

et al. 2016

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We investigated peculiarities of absorption, emission and photonic density of states of a cholesteric liquid crystal with an isotropic defect inside. The influence of the defect position on absorption and emission in the system was studied. It is shown that for non-diffracting circularly polarized incident light absorption/emission is maximum if the defect is in the centre of the system; and for diffracting circularly polarized incident light absorption/emission is maximum if the defect is shifted from the centre of the system to its left border from where light is incident. We also investigated influence of the defect layer thickness and those parameters which characterize absorption and gain on absorption and emission. The influence of anisotropic absorption in the cholesteric liquid crystal layer on photonic states of density was investigated, too.

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“…Two different methods are commonly used to make circularly polarized light: 1) insertion of a quarter wave film after a linear polarizer and 2) generation of Bragg reflection from cholesteric liquid crystals . For some purposes, such as full‐color reflective displays, brightness enhancement films, multiwavelength lasers, or “smart” windows in buildings, where control over the solar spectrum is desired, the working bandwidth should cover a broad range . However, owing to the limited birefringence values available in organic mesomorphic compounds, the spectral width of polarizers made from cholesteric liquid crystals is often limited to only a few nanometers .…”

Section: Methodsmentioning

confidence: 99%

Broadband Circular Polarizing Film Based on Chiral Nematic Liquid Crystals

Cao

Hamad

MacLachlan

2018

Advanced Optical Materials

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polarizers use birefringent crystals requiring a specific thickness and suffer from bulky configurations, [13] many efforts have focused on cholesteric liquid crystals, such as cholesteric polymer networks with a pitch gradient, [14][15][16] or have focused on newly functional optical materials such as compact 3D gold helix metamaterials [3,17,18] and broadband graphene fiber polarizers. [19] Because these approaches are costly and challenging to scale, an inexpensive and straightforward method to achieve broadband circular polarization is in demand.Cellulose is the most abundant biopolymer in nature and can be produced from several natural resources, including plants, tunicates, or bacteria. [20,21] Treatment of extracted cellulose fibers with sulfuric acid produces cellulose nanocrystals (CNCs) with negatively charged sulfate half-ester surface groups. [22,23] This surface charge, whose electrostatic repulsion allows CNCs to form stable colloidal dispersions in water, gives CNCs unique selfassembling properties. Above a critical concentration, CNCs spontaneously organize into a chiral nematic lyotropic liquid crystal, and the structure is retained in films of CNCs following evaporation of the water. [24,25] This chiral nematic mesophase is characterized by stacked layers of oriented CNC spindles, where the orientations of the spindles within the layers rotate with a characteristic twist. Because of the structure, the films behave as 1D photonic crystals, reflecting circularly polarized light having the same sense as the cholesteric screw orientation. [26] This property of CNCs is attractive for producing iridescent films with many potential applications. [27][28][29][30][31][32][33][34] The wavelength reflected from a chiral nematic structure depends on a modified Bragg's Law, λ = nPcosθ, [35] where n is the average refraction index, P is the helical pitch length, and θ corresponds to the angle between incident light propagation direction and the helix axis. Thus, for a specified refractive index (usually determined by the components), the wavelength of the reflected light varies as a function of θ and P. As a result, both nonuniform pitch lengths and a distribution of helical axis orientations would lead to wide-band reflection.For lyotropic liquid crystals of CNCs, the assembly from an isotropic phase into a dense, anisotropic layered structure is a dynamic process that can be influenced by factors such as the pH, ionic strength, additives, and surface tension. [36][37][38][39] This dynamic self-assembly opens the path to introducing defects into the CNC films that lead to different pitches and/or orientations, giving a variety of reflection bands. In this work, we designed a micelle-assisted assembly approach to modulate the Films capable of broadband circular polarization of light are important for many optical applications. Owing to their intrinsic chiral nematic mesostructure, freestanding films of cellulose nanocrystals can reflect circularly polarized light, but this is typically restricted to a narrow ...

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Multi-wavelength laser from dye-doped cholesteric polymer films

Cited by 17 publications

References 24 publications

Tuning the concentration of dye loaded polymer films for maximum photosensitization efficiency: phloxine B in poly(2-hydroxyethyl methacrylate)

Tuning the concentration of dye loaded polymer films for maximum photosensitization efficiency: phloxine B in poly(2-hydroxyethyl methacrylate)

Absorption and emission in defective cholesteric liquid crystal cells

Broadband Circular Polarizing Film Based on Chiral Nematic Liquid Crystals

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