ABSTRACT
Real-time characterization of microresonator dynamics is important for many applications. In particular, it is critical for near-field sensing and understanding light-matter interactions. Here, we report camera-facilitated imaging and analysis of standing wave patterns in optical ring resonators. The standing wave pattern is generated through bidirectional pumping of a microresonator, and the scattered light from the microresonator is collected by a short-wave infrared (SWIR) camera. The recorded scattering patterns are wavelength dependent, and the scattered intensity exhibits a linear relation with the circulating power within the microresonator. By modulating the relative phase between the two pump waves, we can control the generated standing waves' movements and characterize the resonator with the SWIR camera. The visualized standing wave enables subwavelength distance measurements of scattering targets with nanometer-level accuracy. This work opens broad avenues for applications in on-chip near-field (bio)sensing, real-time characterization of photonic integrated circuits, and backscattering control in telecom systems.
ABSTRACT
A simple method of fabricating Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) deep grooves with high aspect ratios using an 800-nm femtosecond laser with chemical-selective etching is demonstrated. The 567-µm-deep grooves with aspect ratios of approximately 35 were obtained with no cracks or thermal affected zone. The morphologies and chemical compositions of grooves were analyzed by a scanning electron microscope with an energy dispersive x-ray spectrometer. The formation mechanism of PMN-PT grooves is attributed to the chemical reactions of hydrochloric acid (HCl) and laser-induced structural changes (LISCs). PMN-PT in LISC became amorphous or mixtures of metal oxide from crystal and all the compounds could react with concentrated HCl and form soluble matter, leaving no precipitation. Furthermore, influences of laser irradiation parameters on depths and aspect ratios of grooves are studied.
ABSTRACT
Electrocaloric refrigeration utilizing ferroelectrics has recently gained tremendous attention because of the urgent demand for solid-state cooling devices. However, the low room-temperature electrocaloric effect and narrow operation temperature window hinder the implementation of lead-free ferroelectrics in high-efficiency cooling applications. In this work, chemical engineering and thick-film architecture design strategies were integrated into a BaTiO3-based system to resolve this challenge. Novel environmental-friendly Ba(Zr0.20Ti0.80)O3-Ba(Sn0.11Ti0.89)O3 (BZT-BST) bilayer films of â¼13 µm in single-layer thickness were prepared by the tape casting process. A giant adiabatic temperature change, Δ T â¼ 5.2 K, and a large isothermal entropy change, Δ S â¼ 6.9 J kg-1 K-1, were simultaneously achieved at room temperature based on the direct measurements, which are much higher than those reported previously in many lead-free ferroelectrics. Moreover, the BZT-BST thick films exhibited a remarkably widened operation temperature range from about 10 to 60 °C. These outstanding properties were mainly attributed to the multiphase coexistence near room temperature, relaxor ferroelectric characteristics, and improved electric-field endurance of the bilayer thick films. This work provides a guideline for the development of environment-friendly electronic materials with both ultrahigh and stable electrocaloric performance and will broaden the application areas of lead-free ferroelectrics.
ABSTRACT
The surface plasmon polaritons (SPPs) have many potential application due to their local field enhancement and sub-wavelength characteristics. Recently, the gradient metasurface is introduced to couple the spoof SPPs in microwave frequency band. One of the most important issue which should be solved is the narrowband of spoof SPPs coupling on the gradient metasurface. Here, the metasurface is proposed to achieve the wideband helicity dependent directional spoof SPPs coupling for circular polarized light. Our research show that the coupling frequency of spoof SPPs on the gradient metasurface is determined by the dispersion of the metasurface, so the coupling frequency can be controlled by dispersion design. The careful design of each cell geometric parameters has provided many appropriate dispersion relations possessed by just one metasurface. The wave vector matching between the propagating wave and the spoof SPPs has been achieved at several frequencies for certain wave vector provided by the metasurface, which leads to wideband spoof SPPs coupling. This work has shown that wideband helicity dependent directional spoof SPPs coupling has been achieved with a high efficiency. Hence, the proposed wideband spoof SPPs coupling presents the improvement in practice applications.
