Low-threshold and high efficiency lasing upon band-edge excitation in a cholesteric liquid crystal

Matsuhisa, Yuko; Huang, Yuhua; Zhou, Ying; Wu, Shin‐Tson; Ozaki, Ryotaro; Takao, Yuuki; Fujii, Akihiko; Ozaki, Masanori

doi:10.1063/1.2710777

Cited by 74 publications

(37 citation statements)

References 22 publications

(18 reference statements)

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“…[51] Because of such altered light-matter interaction, dramatic gain-enhancements in light emitting devices and low threshold and high efficiency lasing have been demonstrated, including the simultaneous lasing of various colors in different directions of the photonic crystal [52] , and lasing at the band-edge of a cholesteric liquid crystal. [53,54] The emission enhancement arises as a result of the reduced photon group velocity and increased photon density of states at the band edge, combined with the inhibition of emission at the photonic stop band. Slow photons have also been employed to drastically enhance the electro-optic response of lithium niobate, where an observed enhancement of 312 times at the band-edge of the photonic crystal suggested the possibility of micron sized nonlinear devices with very low power requirement.…”

Section: Examples Of Photonic Band-edge Enhancementmentioning

confidence: 99%

Amplified Photochemistry with Slow Photons

et al. 2006

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Slow photon, or light with reduced group velocity, is a unique phenomenon found in photonic crystals that theoreticians have long suggested to be invaluable for increasing the efficiency of light-driven processes. This thesis demonstrates experimentally the feasibility of using slow photons to optically amplify photochemistry of both organic and inorganic systems. The effect of photonic properties on organic photochemistry was investigated by tracing out the wavelength-dependent rate of photoisomerization of azobenzene anchored on silica opals. The application of slow photons to inorganic photochemical processes was realized by molding nanocrystalline titania into an inverse opal structure and investigating its photodegradation efficiency in relation to the photonic properties. Changes in the photodegradation efficiency were directly linked to modifications of the electronic band gap absorption as a result of the photonic properties.The highest enhancement of twofold was achieved when the energy of the slow photons overlaps with the electronic band gap absorption, such that the loss of light due to photonic stop-band reflection was significantly reduced. In addition, the strength of slowphoton amplification with respect to the macroscopic structural order was studied by ii introducing controlled disorder via the incorporation of guest spheres into the opal templates. For the first time, a correlation between structural order, photonic properties and a photochemical process was established. The ability to combine slow-photon optical amplification with chemical enhancement was further achieved by incorporating platinum nanoparticles in inverse titania opals where the platinum nanoparticles increased the lifetimes of the higher population of electron-hole pairs arising from slow photon.Overall, various important factors governing the slow photon enhancement were investigated in detail, including the energy of the photonic stop band, angle dependence, thickness of the film, degree of structural order, filling fraction of the dielectric material and diffusion of a second medium if present. Theoretical calculations based on scalarwave approximation in support of the experimental findings were provided wherever possible. The findings provide a blueprint for achieving optical amplification using slow photons in the broad range of photochemical or photophysical processes.iii

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Section: Examples Of Photonic Band-edge Enhancementmentioning

confidence: 99%

Amplified Photochemistry with Slow Photons

et al. 2006

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“…The corresponding observation would be much more difficult to do at a purely numerical approach. Note,that the lowering of the lasing threshold due to the "anomalously strong absorption effect" at the edge mode frequency was observed recently for the collinear [27] and noncollinear [28] geometry of lasing.…”

Section: Resultsmentioning

confidence: 93%

Low Threshold DFB Lasing in Chiral Liquid Crystals

Belyakov

2008

Ferroelectrics

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A brief survey of the recent experimental and theoretical results on the low threshold distributed feedback (DFB) lasing in chiral liquid crystals (CLC) as well as new original theoretical results in the field are presented. The presentation is concentrated on the lasing thresholds at frequencies corresponding to the stop band edge lasing modes and defect modes in CLC. It is demonstrated that the analytic approach reproduces all features of the DFB lasing in CLC obtained by the traditional numerical approach and, more over, allows to reveal some qualitative effects escaped from the researchers employing the numerical methods. Namely, the effect of anomalously strong absorption at the defect mode frequency, a direct analogue of the corresponding effect at the stop band edge mode frequency, is predicted in the framework of the analytic approach. It is proposed also to reduce the lasing threshold by adjusting the pumping wave to the conditions of the anomalously strong absorption effect at the defect mode frequency. The developed approach helps to clarify the physics of lasing at the stop band edge and defect modes in CLC and manifests an agreement with the corresponding results of the previous investigations obtained by a numerical approach.

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“…The corresponding frequencies were associated with, so called ''edge lasing modes'' [1]. It happens also that at the same edge lasing mode frequencies an anomalously strong absorption of the pumping wave occurs [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Edge Modes in Chiral Liquid Crystals: Options for Low Threshold Lasing

Belyakov

Semenov

2009

Molecular Crystals and Liquid Crystals

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An analytic theory of the localized edge modes (EM) in chiral liquid crystals (CLC) is developed. Equations determining the edge mode frequencies are found and analytically solved for the case of low decaying modes and solved numerically for the problem parameters values typical for the experiment. The discrete EM frequencies specified by the integer numbers n are located close to the stop band edge frequencies outside the band. The expressions for space distribution of the n's mode field in CLC layer and for its temporal decay are presented. The possibilities of reduction of the lasing threshold due to the anomalously strong absorption effect are theoretically investigated for a distributed feedback lasing in CLC. It is shown that a minimum of the threshold pumping wave intensity may be reached, generally, for the pumping wave propagating at an angle to the helical axes. However, for lucky values of the related parameters it may be reached for the pumping wave propagating along the helical axis. The lowest threshold pumping wave intensity occurs for the lasing at the first low frequency band-edge lasing mode and the pumping wave propagating at an angle to the spiral axes corresponding to the first absorption maximum of the anomalously strong absorption effect at the high frequency edge of stop band. The corresponding analytical study is performed for the case of the average dielectric constant of LC coinciding with the dielectric constant of the material limiting LC. Numerical calculations of the DFB lasing threshold at EM frequencies are performed for the typical values of the related parameters.

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Low-threshold and high efficiency lasing upon band-edge excitation in a cholesteric liquid crystal

Abstract: How doping a cholesteric liquid crystal with polymeric dye improves an order parameter and makes possible low threshold lasing

Cited by 74 publications

References 22 publications

Amplified Photochemistry with Slow Photons

Amplified Photochemistry with Slow Photons

Low Threshold DFB Lasing in Chiral Liquid Crystals

Edge Modes in Chiral Liquid Crystals: Options for Low Threshold Lasing

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