Thermal modeling of electrically-pumped continuous-wave microring resonator-based topological insulator lasers.

Deleterious effects caused by Joule heating in electrically-pumped continuous-wave InP-based topological insulator lasers based on two-dimensional microring resonator arrays are estimated in this theoretical study. Steady-state temperature distributions within such an array are developed using a full numerical solution. Thermal interactions between active gain regions and ring resonators pose significant operational and integration challenges, as these devices are extremely sensitive to temperature-induced changes in a material's index of refraction. Designing such an array benefits from clear understanding on the effects of systematic non-uniform heating profiles due to temperature variations among the rings. This paper first presents the thermal modeling of a single isolated ring under electrical pumping and then discusses its impact on an operational array composed of 10 × 10 such rings. The simulation results reported here were benchmarked against experimental measurements of the mircoring lasers, wherever possible. Calculations based on a tight-binding model for the array suggest that the laser exhibits single-mode optical output with the preservation of topological properties up to 4 times the threshold current. The useful operating range of the array is mainly limited by the thermal shifts of wavelengths in addition to the wavelength disorders due to fabrication imperfections.

Rh/InGaN1-xOx nanoarchitecture for light-driven methane reforming with carbon dioxide toward syngas.

Light-driven dry reforming of methane toward syngas presents a proper solution for alleviating climate change and for the sustainable supply of transportation fuels and chemicals. Herein, Rh/InGaN1-xOx nanowires supported by silicon wafer are explored as an ideal platform for loading Rh nanoparticles, thus assembling a new nanoarchitecture for this grand topic. In combination with the remarkable photo-thermal synergy, the O atoms in Rh/InGaN1-xOx can significantly lower the apparent activation energy of dry reforming of methane from 2.96 eV downward to 1.70 eV. The as-designed Rh/InGaN1-xOx NWs nanoarchitecture thus demonstrates a measurable syngas evolution rate of 180.9 mmol gcat-1 h-1 with a marked selectivity of 96.3% under concentrated light illumination of 6 W cm-2. What is more, a high turnover number (TON) of 4182 mol syngas per mole Rh has been realized after six reuse cycles without obvious activity degradation. The correlative 18O isotope labeling experiments, in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and in-situ diffuse reflectance Fourier transform infrared spectroscopy characterizations, as well as density functional theory calculations reveal that under light illumination, Rh/InGaN1-xOx NWs facilitate releasing *CH3 and H+ from CH4 by holes, followed by H2 evolution from H+ reduction with electrons. Subsequently, the O atoms in Rh/InGaN1-xOx can directly participate in CO generation by reacting with the *C species from CH4 dehydrogenation and contributes to the coke elimination, in concurrent formation of O vacancies. The resultant O vacancies are then replenished by CO2, showing an ideal chemical loop. This work presents a green strategy for syngas production via light-driven dry reforming of methane.