We demonstrated a low loss 1 × 8 silica-based phased array switch with low power consumption by optimizing the number of arrayed waveguides. To reduce the single-mode fiber coupling loss and to obtain a large coupling tolerance, we introduced triple-branched spot-size converters designed with the wavefront matching method. In addition, heat insulating grooves and a 2π shift-controlled procedure were adopted to reduce the switching power. As a result, we obtained a low insertion loss of 3.6–6.8 dB and a low power consumption of 1.6 W. The polarization dependence, extinction ratio and switching time were 0.1 dB, 17.4–38.6 dB, and 1.2 ms, respectively.
Homologous compounds, Fe 2 O 3 (ZnO) m , with the modulated natural superlattice structure were obtained within a short period by solid state reaction of component oxides under 2.45 GHz microwave irradiation. TEM observation revealed that two types of superlattice structures were observed in different Fe concentration; one is longitudinal superlattice structure in a rod shaped precipitation at high Fe concentration, and the other is modulated structure showing zigzag shape at low Fe concentration. It is conclude that the non-equilibrium nature of microwave selective heating, as well as rapid heating and quenching effects, plays a key role to form the superstructure. The obtained products exhibit ferromagnetic behavior with the Curie temperature above 300 K.
We experimentally demonstrated a 1 × 8 silicon–silica hybrid thermo-optic switch based on an optical phased array using a multi-chip integration technique. The switch consists of a silicon chip with optical phase shifters and two silica-based planar lightwave circuit (PLC) chips composed of optical couplers and fiber connections. We adopted a rib waveguide as the silicon waveguide to reduce the coupling loss and increase the alignment tolerance for coupling between silicon and silica waveguides. As a result, we achieved a fast switching response of 81 µs, a high extinction ratio of over 18 dB and a low insertion loss of 4.9–8.1 dB including a silicon–silica coupling loss of 0.5 ± 0.3 dB at a wavelength of 1.55 µm.
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