This letter examines a planar cholesteric cell ͑CLC͒ doped with two collocated laser dyes as a one-dimensional photonic crystal. Adding phototunable chiral material ͑AzoB͒ allows the CLC photonic crystal to be lased at the band edges of the photonic band gap with a tuning range of over 100 nm. Tuning is performed by irradiating the chiral AzoB material with UV light, causing the material to undergo trans-cis isomerization in the CLC film. The tuning range is the visible region from 563 to 667 nm. Moreover, the tuning is reversible.
In this letter, with an electric double layer on the surface of spherical viruses, we confirm that one of the microwave resonant absorption ͑MRA͒ mechanisms of viruses is through dipolar coupling with confined acoustic vibrations. By treating spherical virions as free homogeneous nanoparticles, we found that the MRA frequencies agree well with that of l = 1 dipolar modes predicted by the elastic continuum theory. The magnitude of MRA was also found to change with the amount of adsorbed charges on the surface of virions. Our results provide a method to observe three-dimensionally confined acoustic vibrations in biological systems.
This work examines a planar cholesteric liquid crystal ͑CLC͒ cell with a negative dielectric anisotropy, doped with laser dye, as an electrically tunable one-dimensional photonic crystal laser device. The lasing wavelength is demonstrated to be tunable by applying a voltage. Additionally, lasing can be switched on and off changing the frequency of the applied voltage. Wavelength tuning caused by the shift of the reflection band of CLC is attributed to the electrohydrodynamical effect in the negative dielectric cell.
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