Antireflection and light-trapping coatings are important parts of photovoltaic architectures, which enable the reduction of parasitic optical losses, and therefore increase the power conversion efficiency (PCE). Here, we propose a novel approach to enhance the efficiency of perovskite solar cells using a light-trapping electrode (LTE) with non-reciprocal optical transmission, consisting of a perforated metal film covered with a densely packed array of nanospheres. Our LTE combines charge collection and light trapping, and it can replace classical transparent conducting oxides (TCOs) such as ITO or FTO, providing better optical transmission and conductivity. One of the most promising applications of our original LTE is the optimization of efficient bifacial perovskite solar cells. We demonstrate that with our LTE, the short-circuit current density and fill factor are improved for both front and back illumination of the solar cells. Thus, we observe an 11% improvement in the light absorption for the monofacial PSCs, and a 15% for the bifacial PSCs. The best theoretical results of efficiency for our PSCs are 27.9% (monofacial) and 33.4% (bifacial). Our study opens new prospects for the further efficiency enhancement for perovskite solar cells.

Fabry–Perot (FP) lasers with a cavity length shorten down to 50 µm were investigated. One or two laser mirrors were formed by focused ion beam etching. InGaAs quantum dots of high density were used as the laser active region. The lasers operate in a pulsed regime up to at least 105°С. A comparison with lasers formed by the facet cleaving method (minimum length is 100 µm) reveals the similarity of the emission wavelength and the threshold current depending on the cavity length. This allows us to conclude that the etched facets do not significantly affect the non-radiative recombination rate and provide a reflection coefficient close to that of the cleaved facet. The maximum modal gain was estimated to be not less than 240 cm⁻¹. No evidence of the excited-state lasing was found.

Nowadays all-dielectric nanophotonics is a powerful tool for improvement light management of thin-film optoelectronic devices because of low optical losses

Spectral characteristics of quantum dot (QD) microdisk lasers under spatially inhomogeneous optical excitation are investigated. By varying the position and size of the continuous-wave excitation spot over the laser cavity, we demonstrate controllable selection and switching of lasing whispering gallery modes (WGMs) at room temperature. Experimental results show that shifting the excitation spot across the surface of 10 μm microdisk laser enables reversible wavelength switching between WGMs at 1285 nm and 1313 nm, corresponding to different radial mode orders. Theoretical modeling and near-field scanning optical microscopy confirm that the observed spectral switching of lasing WGM is caused by spatially selective charge carrier distribution arising from the suppressed lateral transport of charge carriers in quantum dot active region. The findings highlight the potential for actively spectral switchable microlasers for applications in photonic integration and optical sensing.

We report high-efficiency and compact semiconductor microcavity lasers with limaçon-shaped geometry operating in continuous-wave mode. The lasers, with radii (r0) ranging from 10 to 25 μm, were formed using a p-i-n heterostructure with an active region based on high-density InGaAs/GaAs quantum dot array, emit at a wavelength near 1080 nm at room temperature. Using smooth cavity deformation with a deformation factor up to ε = 0.46, we achieved directional emission output in the plane of the cavity. Single-mode lasing with an output power of up to 2 mW, limited by the laser self-heating effect, is demonstrated for a laser with a radius of r0 = 10 μm. For larger lasers (r0 = 25 μm), operating in multimode regime, an output power reaches 10 mW. The resonator maintains a high Q of 2×10^(6), enabling a laser linewidth of 150 MHz. The obtained results demonstrate the potential of such microlasers as highly stable and energy-efficient radiation sources suitable for integration into modern photonic circuits.

We demonstrate a thermo-optically tunable microlaser based on an InGaAs/GaAs quantum-dot (QD) active region employing a deformed limaçon-shaped cavity. The asymmetric geometry effectively lifts the degeneracy of high- Q whispering-gallery modes, enabling single-mode lasing. A side-mode suppression ratio exceeds 25 dB over a wide current range. Under continuous-wave electrical pumping, the device achieves a peak output power of ∼0.4 mW, which is 1.5 times higher than that of a circular microdisk of comparable size, due to enhanced directional out-coupling. By exploiting self-heating via injection current control, we realize continuous wavelength tuning over a mode-hop-free range of 4.6 nm with a tuning coefficient of ∼0.3 nm mA ⁻¹ . In addition, complementary temperature-dependent measurements under pulsed current injection with externally controlled stage heating were performed to independently characterize the thermal response of the device. These measurements reveal a linear wavelength shift with a thermal tuning coefficient of 0.073 nm K ⁻¹ . Experimental results are supported by finite-element method simulations, which confirm a significant reduction in the number of competing cavity modes as the cavity deformation parameter increases. The combination of single-mode operation, efficient power output, and electrically controlled thermo-optic tuning makes these limaçon-shaped QD microlasers promising candidates for compact, tunable light sources in photonic integrated circuits and sensing applications.