Showing papers by "Lan Yang published in 2023"
TL;DR: In this article , the solar-reflective and infrared-radiative properties of Sr-doped BaTiO3 are studied systematically, and the lowest absorptivity-emissivity ratio of 0.24 was observed for Ba0.8Sr0.2 TiO3.
TL;DR: In this paper , the authors theoretically and experimentally demonstrate that by steering a single microresonator with thermo-optic nonlinearity to chiral EPs, non-reciprocal light propagation is achieved with an isolation ratio up to 24 dB and insertion loss less than 0.5 dB.
Abstract: On-chip optical nonreciprocity is one of the essential functions to fully advance the development of integrated optical systems, which remains technically challenging in many aspects. There is a great need for mechanisms and approaches to facilitate the large-scale implementation of nonreciprocal light propagation. Recently, unconventional phenomena, such as chiral optical modes and directional light propagation, have been unraveled at exceptional points (EPs), which are unique degeneracies in the energy spectrum and eigenspace of non-Hermitian systems. Here, this work theoretically and experimentally demonstrates that by steering a single microresonator with thermo-optic nonlinearity to chiral EPs, nonreciprocal light propagation is achieved with an isolation ratio up to 24 dB and insertion loss less than 0.5 dB. The nonreciprocity is dependent on the chirality and could be optimized near the EPs. Their results pave new avenues for the nonreciprocal control of light propagation enabled by non-Hermitian degeneracies and hold great potential for microscale and nanoscale on-chip nonreciprocal devices.
TL;DR: In this paper , the electronic bandgaps, phononic structures, optical-spectrum properties, and formation energies of 76 kinds of phase-changing ABO3 perovskites were predicted based on first-principles calculations in the mid-infrared region.
Abstract: Phase-change thermal control has recently seen increased interest due to its significant potential for use in smart windows, building insulation, and optoelectronic devices in spacecraft. Tunable variation in infrared emittance can be achieved by thermally controlling the phase transitions of materials at different temperatures. A high emittance in the mid-infrared region is usually caused by resonant phonon vibrational modes. However, the fundamental mechanism of emittance variation during the phase-change process remains elusive. In this work, the electronic bandgaps, phononic structures, optical-spectrum properties, and formation energies of 76 kinds of phase-changing ABO3 perovskites were predicted based on first-principles calculations in the mid-infrared region. The variation in emittance between two phases of a single material was found to have an exponential correlation with the bandgap difference (R2 ∼ 0.92). Furthermore, a strong linear correlation (R2 ∼ 0.92) was found between the emittance variation and the formation-energy difference, and the emittance variation was also strongly correlated with the volume-distortion rate (R2 ∼ 0.90). Finally, it was concluded that a large lattice vibrational energy, a high formation energy, and a small cell volume are conducive to high emittance. This work provides a strong dataset for training machine-learning models, and it paves the way for further use of this novel methodology to seek efficient phase-change materials for thermal control.