Feasibility of Non-Collinear TeO2 Acoustic-Optic Tunable Filters Used in the Optical Communication

The characteristics and the structure of TeO2 acoustic-optic tunable filter used in communication are discussed briefly based on the acoustic-optic theory and it is shown that a large optical incident angle and a long interaction length are suitable for the optical add/drop multiplexer based on the TeO2 acoustic-optic tunable filter. The distribution of acoustic energy flow in the device supports the large optical incident angle. The long interaction length depends on the change of the device structure to some degree. The measured results of the samples show that the diffraction efficiency reaches at 96% in the tuning range larger than lOOnm and the bandwidth is about 2nm. It can be found that there is a good consistency with the basic theoretical mode. The optimized design result shows that the diffraction efficiency can arrive at 100%, and the bandwidth can be less than 0.4nm. Thus, the non-collinear TeO2 acoustic-optic tunable filter can play an important role in the coming general optical network.     

Hrmander Type Theorem for Fourier Multipliers with Optimal Smoothness on Hardy Spaces of Arbitrary Number of Parameters

The main purpose of this paper is to establish the Hormander-Mihlin type theorem for Fourier multipliers with optimal smoothness on k-parameter Hardy spaces for k≥ 3 using the multiparameter Littlewood-Paley theory. For the sake of convenience and simplicity, we only consider the case k = 3, and the method works for all the cases k≥ 3:■where x =(x_1,x_2,x_3)∈R~(n_1)×R~(n_2)×R~(n_3) and ξ =(ξ_1,ξ_2,ξ_3)∈R~(n_1)×R~(n_2)×R~(n_3). One of our main results is the following:Assume that m(ξ) is a function on R~(n_1+n_2+n_3) satisfying ■ with s_i n_i(1/p-1/2) for 1≤i≤3. Then T_m is bounded from H~p(R~(n_1)×R~(n_2)×R~(n_3) to H~p(R~(n_1)×R~(n_2)×R~(n_3)for all 0 p≤1 and ■ Moreover, the smoothness assumption on s_i for 1≤i≤3 is optimal. Here we have used the notations m_(j,k,l)(ξ)=m(2~jξ_1,2~kξ_2,2~lξ_3)Ψ(ξ_1)Ψ(ξ_2)Ψ(ξ_3) and Ψ(ξ_i) is a suitable cut-off function on R~(n_i) for1≤i≤3, and W~(s_1,s_2,s_3) is a three-parameter Sobolev space on R~(n_1)×R~(n_2)× R~(n_3).Because the Fefferman criterion breaks down in three parameters or more, we consider the L~p boundedness of the Littlewood-Paley square function of T_mf to establish its boundedness on the multi-parameter Hardy spaces.     

Irradiation-assisted photoelastic domain wall formation in X- and Y-cut lithium niobate

Irradiation-assisted photoelastic domain wall formation in single-crystalline X- and Y-cut lithium niobate (LNO) is studied at low displacement doses, namely, up to a maximum of 2.5×10⁻² dpa and annealed at 270 °C. The formation of surface ridges (or striations) is observed and quantified using atomic force and optical microscopy. In spite of the different crystallographic orientation of the two single-crystals a correlation between the density of surface defects and the displacement dose is established phenomenologically which means that the displacement damage and its consequent defect accumulation behavior prior to annealing (‘incubation phase’) defines to which extent the lattice undergoes an irreversible mechanical deformation immediately after annealing. This ridge formation mechanism assisted by irradiation and moderate annealing constitutes a fine tool to modify the near-surface structure and the local optical properties of LNO and hence it allows one to potentially micromachine new photonic devices.     

Composite-meson model and meson exchange currents

We study the meson exchange currents (MEC) mechanism for the pion double-charge exchange (DCX) reaction in a composite-meson model. The model assumes that the mesons are two-quark systems and can interact with each other only through quark loops. The contributions of the ρ, σ, and f₀ mesons, the four-quark box diagram as well as a contact diagram has been taken into account. It is shown that the contribution of the ρ, σ, and f₀ mesons increases the forward scattering cross-section in an average by 25% and decreases with energy.     

Systematic considerations for the patterning of photonic crystal devices by electron beam lithography

Photonic crystal devices with feature sizes of a few hundred nanometers are often fabricated by electron beam lithography. The proximity effect, stitching error and resist profiles have significant influence on the pattern quality, and therefore determine the optical properties of the devices. In this paper, detailed analyses and simple solutions to these problems are presented. The proximity effect is corrected by the introduction of a compensating dose. The influence of the stitching error is alleviated by replacing the original access waveguides with taper-added waveguides, and the taper parameters are also discussed to get the optimal choice. It is demonstrated experimentally that patterns exposed with different doses have almost the same edge-profiles in the resist for the same development time, and that optimized etching conditions can improve the wall angle of the holes in the substrate remarkably.     

Isotope effects in the metastable decay of Ne2 +

Neon dimer ions undergo spontaneous dissociation (metastable decay) several microseconds after formation by electron impact ionization of neon clusters. In this contribution we compare the kinetic energy release distribution (KERD) of the previously reported isotopomer ²⁰Ne₂ ⁺ with that of ²²Ne₂ ⁺. The heavy isotopomer shows the same two components in the KERD as the lighter ones. However, the high-energy component that is due to electronic pre-dissociation is reduced in intensity. The decrease is attributed to a reduced predissociation rate from the II(1/2u) state into I(3/2u).     

HORMANDER MULTIPLIER THEOREM ON SU(2)

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Understanding the solar photo-catalytic activity of TiO2-ITO nanocomposite deposited on low cost substrates

In this work, we report on the photo-catalytic properties of TiO₂-ITO nanocomposite deposited on low cost conventional clay ceramic substrates. The nanocomposite was formed by spraying a solution prepared from the P25 TiO₂ powder (Degussa) mixed with an organometallic paste of a dissolved combination of indium and tin. A TiO₂-ITO powder-like nanocomposite was prepared for X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization. The mean particle size of the TiO₂-ITO nanocomposite was found to be larger than that of pure TiO₂. The optical features of TiO₂-ITO-based layers (deposited on glass substrates) were investigated using UV-vis spectroscopy. The TiO₂-ITO nanocomposite deposited layers were found to have higher light absorption than the P25 TiO₂ powder. The photo-catalytic properties of the TiO₂-ITO nanocomposite (deposited on low cost clay ceramic substrates) were tested under solar irradiation using a well-known polluting dye. It was shown that the TiO₂-ITO nanocomposite exhibits higher degradation rates towards the pollutant dye than the P25 TiO₂ powder. The optical band gap of the TiO₂-ITO nanocomposite (2.79 eV) was found to be lower than that of pure TiO₂ (3.1 eV), while ITO (indium tin oxide) has a band gap of about 4.2 eV. ITO was found to be entirely transparent to sun light, while it exhibits a slight photo-catalytic activity, signifying the possible existence of an indirect photo-catalysis phenomenon (sensitized semiconductor photocalysis) and potential degradation (oxidation) of the pollutant through electron transfer from the dye to conduction band of the semiconductor. All photo-catalytic activity results were discussed in light of the optical band gap of the various compounds.     

Nitric acid oxidation method to form SiO2/3C-SiC structure at 120 °C

3C-SiC(0 0 1) surfaces are considerably rough with the roughness root mean square value (R_ms) of 1.3 nm, but the surfaces become considerably smooth (i.e., R_ms of 0.5 nm) by heat treatment in pure hydrogen at 400 °C. Two-step nitric acid (HNO₃) oxidation (i.e., immersion in ∼40 wt% HNO₃ followed by that in 68 wt% HNO₃) performed after the hydrogen treatment can oxidize 3C-SiC at extremely low temperature of ∼120 °C, forming thick SiO₂ (e.g., 21 nm) layers. With no hydrogen treatment, the leakage current density of the 〈Al/SiO₂/3C-SiC〉 metal-oxide-semiconductor (MOS) diodes is high, while that for the MOS diodes with the hydrogen treatment is considerably low (e.g., ∼10⁻⁶ A/cm² at the forward gate bias of 1 V) due to the formation of uniform thickness SiO₂ layers. The MOS diodes with the hydrogen treatment show capacitance-voltage curves with accumulation, depletion, and deep-depletion characteristics.