Photonic integration based on a ferroelectric thin-film platform.

Photonic-integrated circuits (PICs) using ferroelectric materials are expected to be used in many applications because of its unique optical properties such as large electro-optic coefficients. In this study, a novel PIC based on a ferroelectric thin-film platform was designed and fabricated, where high-speed optical modulator, spot-size converters (SSCs), and a variable optical attenuator (VOA) were successfully integrated. A ferroelectric lanthanum-modified lead zirconate titanate (PLZT) thin film was epitaxially-grown by using a modified sol-gel method, and it exhibits large electro-optic coefficients (>120 pm/V) and low propagation loss (1.1 dB/cm). The optical modulator, a Mach-Zehnder type, exhibited a half-wave voltage (Vπ) of 6.0 V (VπL = 4.5 Vcm) and optical modulation up to 56 Gb/s. Also, the VOA (with attenuation range of more than 26 dB) was successfully integrated with the modulator. As a result, it is concluded that the developed ferroelectric platform can pave the way for photonic integration.

Circularly Polarized Luminescence from Inorganic Materials: Encapsulating Guest Lanthanide Oxides in Chiral Silica Hosts.

Recently, circularly polarized luminescence (CPL)-active systems have become a very hot and interesting subject in chirality- and optics-related areas. The CPL-active systems are usually available by two approaches: covalently combining a luminescent centre to chiral motif or associating the guest of luminescent probe to a chiral host. However, all the chiral components in CPL materials were organic, although the luminescent components were alternatively organics or inorganics. Herein, the first totally inorganic CPL-active system by "luminescent guest-chiral host" strategy is proposed. Luminescent sub-10 nm lanthanide oxides (Eu2 O3 or Tb2 O3 ) nanoparticles (guests) were encapsulated into chiral non-helical SiO2 nanofibres (host) through calcination of chiral SiO2 hybrid nanofibres, trapping Eu3+ (or Tb3+ ). These lanthanide oxides display circular dichroism (CD) optical activity in the ultraviolet wavelength and CPL signals around at 615 nm for Eu3+ and 545 nm for Tb3+ . This work has implications for inorganic-based CPL-active systems by incorporation of various luminescent guests within chiral inorganic hosts.

Unique solution properties of quaternized oligomeric surfactants derived from ethylenediamine or G0 poly (amidoamine) dendrimers.

New quaternized oligomeric surfactants containing 4 or 8 alkyl chains were synthesized using ethylenediamine or poly(amidoamine) dendrimers as the central scaffold. Electrical conductivity, surface tension, and pyrene fluorescence measurements, as well as dynamic light scattering were used to characterize their properties. In addition, the dependence of these properties on the alkyl chain length, number of chains, and dendrimer generation was determined through comparison with previously reported oligomeric surfactants. The relation between surface tension and concentration for the oligomeric surfactants exhibited clear breakpoints, which reflect the critical micelle concentration (cmc). Both cmc and surface tension were lower than those of monomeric alkyltrimethylammonium bromide surfactants, indicating that the synthesized oligomeric surfactants have excellent micelle-forming ability in solution and high adsorption ability at the air/water interface, in spite of the large bulky structure containing multiple alkyl chains and headgroups within one molecule. When the alkyl chain length or the number of chains of the oligomeric surfactants was increased, a unique behavior was observed in that adsorption at the air/water interface and solution aggregation occurred simultaneously at a concentration below cmc (as determined by the surface tension method). This suggests that aggregate formation occurs readily in solution along with the adsorption at the interface because of strong attractive interactions between multiple alkyl chains.

Surface Chemistry Involved in Epitaxy of Graphene on 3C-SiC(111)/Si(111).

Surface chemistry involved in the epitaxy of graphene by sublimating Si atoms from the surface of epitaxial 3C-SiC(111) thin films on Si(111) has been studied. The change in the surface composition during graphene epitaxy is monitored by in situ temperature-programmed desorption spectroscopy using deuterium as a probe (D(2)-TPD) and complementarily by ex situ Raman and C1s core-level spectroscopies. The surface of the 3C-SiC(111)/Si(111) is Si-terminated before the graphitization, and it becomes C-terminated via the formation of C-rich (6√3 × 6√3)R30° reconstruction as the graphitization proceeds, in a similar manner as the epitaxy of graphene on Si-terminated 6H-SiC(0001) proceeds.

A ramsayite-type oxide, Ca(2)Sn(2)Al(2)O(9).

The title compound, dicalcium nonaoxidodistannate(IV)dialuminate, is the second example which crystallizes in the isotypic structure of a pyroxene silicate, Na(2)Ti(2)Si(2)O(9) (ramsayite). (∞) (1)[Sn(2)O(8)] chains and pyroxene-type (∞) (1)[Al(2)O(6)] chains are formed along the b axis by sharing O atoms. The Ca atoms are situated in the resulting channels and exhibit a coordination number of 7.