This letter describes the electrical control of structure and lasing in the photonic bandgaps of cholesteric liquid crystals (CLCs). Photoexcitation of dye-doped CLC cells with a linearly polarized laser gives rise to laser emission at the edge(s) of the chiral photonic band gap. Applying voltages to the optically pumped CLC cells enables reversible switching of the laser action as a result of the structural changes in the chiral photonic band gap.

Nonlinear optical dendritic macromolecules, called azobenzene dendrons, were synthesized, and their conformational properties and molecular nonlinear optical properties were clarified by second-order nonlinear optical measurement. The synthesized molecules were modified by introducing 1-15 numbers of azobenzene branching units as the nonlinear optical chromophore and by placing aliphatic chains at the end the dendritic chains. In these topologically complex molecules, each chromophore contributed coherently to the macroscopic nonlinear optical activity. The first-order molecular hyperpolarizability of the azobenzene dendron having 15 chromophoric units was measured to be 3010 × 10 -30 esu using the hyper-Rayleigh scattering method. This level of molecular hyperpolarizability was much higher than that for an azobenzene monomer (150 × 10 -30 esu). The polarized nonlinear optical measurement provided structural information on the dendrons and indicated that each chromophore was oriented noncentrosymmetrically along the molecular axis to become a cone shape rather than a spreading or spherical shape. This structure gave rise to a large electronically dipolar macromolecule system, in which each chromophoric unit coherently contributed to the second harmonic generation.

This letter describes the phototunable photonic bandgap of cholesteric liquid crystal (CLC) doped with a fluorescent dye to generate the distributed feedback effect. Photoirradiation of the dye-doped CLC cell under UV light at 254 nm resulted in continuous changes in the chiral photonic bandgap from 550 to 720 nm due to photolysis reaction of the cholesteryl iodide embedded in the CLC host. We showed that the laser oscillation wavelength could be controlled in a wide wavelength range from 610 to 700 nm by photoassisted adjustment of CLC photonic bandgaps.

Heliorhodopsins (HeRs) are a new category of retinal-bound proteins recently discovered through functional metagenomics analysis that exhibit obvious differences from type-1 microbial rhodopsins. We conducted the first detailed structural characterization of the retinal chromophore in HeRs using resonance Raman spectroscopy. The observed spectra clearly show that the Schiff base of the chromophore is protonated and forms a strong hydrogen bond to a species other than a water molecule, highly likely a counterion residue. The vibrational mode of the Schiff base of HeRs exhibits similarities with that of photosensory microbial rhodopsins, that is consistent with the previous proposal that HeRs function as photosensors. We also revealed unusual spectral features of the in-plane chain vibrations of the chromophore, suggesting an unprecedented geometry of the Schiff base caused by a difference in the retinal pocket structure of HeRs. These data demonstrate structural characteristics of the photoreceptive site in this novel type of rhodopsin family.

We report on the development of superconducting nanowire single photon detectors (SNSPDs) by using NbTiN thin films on single crystal MgO substrates. NbTiN thin films showed fine crystal structure with closer lattice constant to MgO substrates than that of NbN thin films. The transition temperature of 3.5-nm-thick NbTiN films was comparable to, and the resistivity at 20 K was lower than NbN thin films. The kinetic inductance of NbTiN-SNSPDs was 25% lower than that of NbN-SNSPD, and system detection efficiency was 1.4% at a 1550 nm wavelength, which is comparable to NbN-SNSPDs.