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Oxide films of the quality required for the fabrication of electronic and photonic devices are typically deposited at elevated temperatures and thermal equilibrium, thereby adversely impacting thermal budgets. We report the deposition and patterning of silicon dioxide (SiO2) films of high electrical and optical quality on Si(100) or polymer substrates in a N2 atmosphere and at 300 K by the photochemical conversion of thin liquid tetraethoxysilane (TEOS) layers with narrowband vacuum ultraviolet radiation [vacuum ultraviolet (VUV), 172 nm] provided by efficient microplasma lamps. Irradiating liquid TEOS layers, produced by spin-coating the precursor onto a substrate, with a VUV intensity of 13 mW cm−2, yields 40 nm-thick SiO2 films having a dielectric breakdown strength (Eb) of 5 MV cm−1, for which no precedent exists in the deposition of oxide films at 300 K. If room temperature-deposited films are post-annealed at 200 °C, Eb rises to 7.5 MV cm−1, which is <12% below the measured value (8.5 MV cm−1) for 40 nm SiO2 films grown by thermal oxidation. The deposition of 1 µm thick, stoichiometric SiO2 films requires only 20 min of VUV illumination at low optical fluences, and films with thicknesses of ∼35–60 nm exhibit a refractive index of 1.45 (633 nm). X-ray photoelectron spectrometry and Rutherford backscattering analysis indicate that, despite the deposition temperature, hydrocarbon impurity levels are near or below the detection limit. The capability for depositing 960 nm-thick SiO2 films uniformly (to within 0.6%) by liquid → solid photochemical conversion over a 5 cm diameter Si substrate and patterning films onto flexible polymer substrates has also been demonstrated. [ABSTRACT FROM AUTHOR]

Two classes of higher-order, fractal spatial eigenmodes have been predicted computationally and observed experimentally in microlasers. The equatorial plane of a close-packed array of microspheres, lying on one mirror within a Fabry-Pérot resonator and immersed in the laser gain medium, acts as a refractive slit array in a plane transverse to the optical axis. Edge diffraction from the slit array generates the high spatial frequencies (>10 4  cm -1 ) required for the formation of high-order laser fractal modes, and fractal transverse modes are generated, amplified, and evolve within the active medium. With a quasi-rectangular (4-microsphere) aperture, the fundamental mode and several higher-order eigenmodes (m = 2,4,5) are observed in experiments, whereas only the m = 1,2 modes are observed experimentally for the higher-loss resonators defined by triangular (3-microsphere) apertures. The fundamental and 2 nd -order modes (m = 1,2) for the 4-sphere aperture are calculated to have qualitatively similar intensity profiles and nearly degenerate resonant frequencies that differ by less than <0.1% of the free-spectral range (375 GHz) but exhibit even and odd parity, respectively. For all of the observed fractal modes, the fractal dimension (D) rises rapidly beyond the intracavity aperture array as a result of the high spatial frequencies introduced into the mode profile. Elsewhere, D varies gradually along the resonator axis and 2.2 < D < 2.5. Generating fractal laser modes in an equivalent optical waveguide is expected to allow the realization of new optical devices and imaging protocols based on the spatial frequencies and variable D values available.

Interatomic potentials for the B 2 Σ 1/2 + states of CsAr, CsXe, and RbXe have been determined through comparisons of experimental B ← X absorption spectra for alkali vapor-rare gas mixtures with calculations of the Franck-Condon factors (FCFs) associated with free-free transitions of thermal atomic pairs. Simulations of optical transitions of alkali-rare gas atomic pairs between the thermal and vibrational continua of the X 2 Σ 1/2 + and B 2 Σ 1/2 + states of the molecule, responsible for the blue satellites of the Cs and Rb D 2 resonance lines in a rare gas background, require the incorporation of ground-state J values above ∼400 into the FCF calculations and proper normalization of the free-particle wave functions. Absorption spectra computed on the basis of several X and B state interatomic potentials available in the literature were found to be sensitive to the height of the B 2 Σ 1/2 + state barrier, as well as the X 2 Σ 1/2 + state repulsive wall contour and the location of the van der Waals minimum. Other spectral simulations entailed iterative modifications to a selected B 2 Σ 1/2 + interatomic potential, again coupled with comparison to experimental B ← X spectra. Comparisons of calculated spectra with experiment yield a CsXe B 2 Σ 1/2 + potential, for example, exhibiting a barrier height of 76 cm -1 at 5.2 Å and yet is nearly flat at smaller values of internuclear separation ( R ). The latter contrasts with previous theoretical calculations of V B ( R ) in the vicinity of the barrier maximum. For the CsAr molecule, the B 2 Σ 1/2 + barrier height was found to be 221 cm -1 , which is within 3% of the value determined from pseudopotential calculations incorporating the spin-orbit effect. Reproducing Cs-rare gas experimental absorption spectra also requires the existence of a broad, shallow potential well lying beyond the B 2 Σ 1/2 + barrier that, for CsAr, has a dissociation energy ( D e ∼ 24 cm -1 ) a factor of 3 larger than values predicted by theory. Similar results are obtained for the RbXe and CsXe complexes.