In this study, strong two-photon absorption (TPA) in a layered bismuth telluride (Bi2Te3) topological insulator (TI) is observed and investigated by the Z-scan method under excitation with a femtosecond laser pulse at a wavelength of 1056 nm.
Simultaneous determination of cysteine (RSH) and cystine (RSSR), two important sulfur-containing amino acids, in capillary electrophoresis (CE) has been an analytical task. Dual-microelectrode amperometric detection seems to be a good scheme, but significant difficulty in electrode construction and poor detection limit for RSSR determination remain major short-comings. In reverse pulse amperometric (RPA) detection, the applied potentials are repeatedly pulsed back and forth between the reducing initial potential (e.g., Ei =-1.4 V) and the oxidizing final potential (e.g., E r =0.0 V) at a single, gold-mercury amalgam (AuIHg) microelectrode. At E;, RSSR is reduced to RSH which Causes catalytical oxidation of the Au/Hg amalgam microelecuode when the potential is pulsed to E f • The resulting anodic current is then recorded. Therefore, by using RPA detection after CE separation, RSH and RSSR can be simultaneously determined.
In this paper, a high temperature wet chemical etching technique to pattern tantalum pentoxide (Ta205) antiresonant reflecting optical ridge waveguides (ARROW) in sodium hydroxide based systems was developed. The Ta2O5 dielectric films were formed by a magnetron RF sputtering technique on a Si substrate. After deposition, the films were etched in hot NaOH and NaOH/H2O2 solutions. The NaOH etchants etched the deposited Ta205 at a relatively high rate (-1 p.m/mm, 100 'C, 40% NaOH solution), but they left an insoluble residue on the substrate. The residue can be reduced either by raising the etchant temperature or by adding hydrogen peroxide to the NaOH solutions. Using the NaOH/H2O2 etchants, we successfully fabricated the ARROW-type ridge waveguides with an undercut of less than 1 p.m for an etching depth of 5 p.' An etching rate of 5 p.m/mm was achieved at 130 'C with a mixture containing 50% NaOH solution and 35% H202.
High-Temperature Wet Chemical Etching of Ta 2 O 5 in NaOH-Based Solutions for Fabricating Antiresonant Reflecting Optical Waveguides. -The Ta 2 O 5 dielectric films are formed by magnetron RF sputtering technique on Si. Etching without insoluble residues occurs by use of NaOH/H 2 O 2 etchant. The etching rates are increased to 5 µm/min with satisfactory undercut control achieved at an etchant temp. of 130 • C. Ta 2 O 5 ARROW-type waveguides with ridge widths ranging from 5 to 20 µm are fabricated. -(CHUANG, M. J.; HSIEH, K. Y.; CHU, A. K.; J.
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