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Abstract
Low threshold laser action of dye-doped cholesteric liquid crystals (CLCs) is demonstrated using an input circularly polarized light whose handedness is the same as the cholesteric helix of the sample at the high-energy band edge of the reflection band. The mechanism originates from the dramatic increase of the photon density of state at the band edges. We also demonstrate an enhanced laser action of a CLC in a dielectric multilayer cavity. In such a device configuration, the band-edge excitation at high-energy band edge improves the lasing performance not only for the same handedness circularly polarized pump beam as the cholesteric helix but also for the opposite one. It stems from the polarization independence of the dielectric multilayers.
Highlights
Photonic crystals, which exhibit an ordered structure with periodic dielectric constant in an optical wavelength range, have attracted much attention from both fundamental and practical points of view [1,2,3,4,5]
The mechanism originates from the dramatic increase of the photon density of state at the band edges
We demonstrate an enhanced laser action of a cholesteric liquid crystals (CLCs) in a dielectric multilayer cavity
Summary
Photonic crystals, which exhibit an ordered structure with periodic dielectric constant in an optical wavelength range, have attracted much attention from both fundamental and practical points of view [1,2,3,4,5]. Dye-doped CLC lasers have been extensively studied by utilizing the suppression of the photon group velocity and the enhancement of the photon density of state at the band edges because of their advantages such as simple fabrication process, wide tuning range, and mirrorless structure [7,8,9,10,11,12,13,14]. The laser efficiency can be improved by choosing laser dyes and liquid crystals with higher order parameters [15] Another approach is to incorporate reflectors to the CLC medium, which decreases the lasing threshold and enhances the lasing efficiency [16,17,18,19,20]. We demonstrate the laser action upon band-edge excitation in the CLC using dielectric mirrors as the reflectors
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