Superfluorescent Squaraine with Efficient Two‐Photon Absorption and High Photostability

The synthesis, linear photophysical, two‐photon absorption (2PA), femtosecond transient absorption, and superfluorescence properties of a new symmetrical squaraine derivative ( 1 ) are reported. Steady‐state linear spectral and photochemical properties, fluorescence lifetimes, and excitation anisotropy of 1 were investigated in various organic solvents. High fluorescence quantum yields (≈0.7) and very high photostability (photodecomposition quantum yields ≈10^?6–10^?8) were observed. An open‐aperture Z‐scan method was used to obtain 2PA spectra of 1 over a broad spectral range (maximum 2PA cross section ≈1000 GM). Excited‐state absorption (ESA) and gain was observed by femtosecond transient absorption spectroscopy, in which both reached a maximum at approximately 500 fs. Squaraine 1 exhibits efficient superfluorescence. The quantum chemical study of 1 revealed the simulated vibronic nature of the 1PA and 2PA spectra were in good agreement with experimental data; this may provide the ability to predict potential advanced photonic materials.     

Single mode ridge waveguides based on vinyltriethoxysilane hybrid sol–gel material

In this work, fabrication and characterization of a single-mode vinyltriethoxysilane (VTES) based hybrid organic–inorganic sol–gel ridge waveguide is reported. VTES based hybrid sol–gel material has been deposited by multiple spin-coating process on quartz substrate. Channel waveguides have been fabricated by UV photopolymerization followed by wet etching process. Optical guided mode was observed to ensure the single mode condition while cut-back technique was performed for loss propagation measurement. Optical propagation losses were measured to be 1.6 dB/cm at 1.31 μm wavelength. This value shows that this material is a promising choice for the development of integrated optical circuits for telecommunication field.     

Horizontally networked carbon nanotubes grown on Au–Fe catalyst nanoparticles

Undoped and doped indium tin oxide (ITO) with different concentrations (2, 4, and 6 mol%) of different dopants (CuO, Cr₂O₃, and ZrO₂) were prepared in the nano-size scale (19–33 nm) using Pechini method. The thermal decomposition of the precursors was studied. The electrical properties of all the prepared samples were investigated. All the investigated systems have higher conductivity than that of ITO. For ITO doped with CuO, as the concentration of CuO increases, the conductivity increases. The highest conductivity was obtained for ITO doped with 6 mol% of CuO. For ITO doped with Cr₂O₃, as the concentration of Cr₂O₃ increases the conductivity increases and above 4 mol% Cr₂O₃ the conductivity decreases. For ITO doped with ZrO₂, as the ZrO₂ concentration increases, the conductivity increases up to 4 mol% of ZrO₂ and then decreases. The band gap was detected for all the investigated systems.     

Extrinsic surface scattering and intrinsic absorption loss of vinyl based hybrid organic–inorganic materials for optical waveguides applications

Hybrid photosensitive materials were prepared by using vinyltriethoxysilane (VTES), tetraethoxysilane (TEOS) and tetrabutoxytitanate (TTBu) precursors through sol–gel technique. The materials are intended for optical telecommunication applications. Thus, high optical transmissions at the second and third optical telecommunication windows are essential. Extrinsic surface scattering due to surface roughness and intrinsic absorption due to aliphatic CH and OH groups are always ascribable to the optical power attenuations at aforementioned optical telecommunication windows. Optical waveguide based on hybrid sol–gel materials were fabricated, characterized and analyzed in order to investigate the extrinsic and intrinsic sources of attenuation and their contributions. The fabricated samples were characterized for propagation loss, surface condition, and Fourier transform IR (FTIR) absorption spectra. Propagation loss were measured by means of cut-back method as 1.6 and 6.9 dB/cm at 1310 and 1550 nm wavelengths, respectively. Surface scattering loss was modeled based on measured rms roughness of 0.724 nm and turned out to contribute less than 0.01% of the total propagation loss. FTIR absorption spectra show the persistent existence of aliphatic CH and OH groups within the final hybrid sol–gel materials.