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Vitalii Sichkovskyi

Publications and source records attributed to Vitalii Sichkovskyi.

5 recordsLinked to original sources
arXiv2026

Optimization of InAs/InAlGaAs/InP quantum dots for O-band laser applications

The O-band telecommunication spectral range combines minimal chromatic dispersion with low transmission loss, making it highly suitable for optical communications. Semiconductor telecom lasers utilizing low-dimensional active regions, such as quantum dots, offer low threshold power and high thermal stability. However, long-wavelength quantum dot emitters often suffer from thermal carrier escape through excited states when the energy separation between the ground and excited states is insufficient. Here we demonstrate the optimization of InAs quantum dot emitters grown on InP by molecular-beam epitaxy for O-band laser active regions. By optimizing the design for better carrier capture efficiency and tuning the emission wavelength to the O-band, we show ways of improving the carrier confinement. Absorption spectroscopy on the finalized structure confirms substantial energy separation between the quantum dot ground and excited states, effectively suppressing thermal carrier escape even at elevated temperatures. These results highlight critical design for improving carrier capture and retention in long-wavelength quantum dot lasers.

cond-mat.mtrl-sci↗
arXiv2025

On the relationship between noise squeezing and Rabi oscillations in active quantum dot ensembles

Squeezed light is usually generated using passive nonlinear materials. Semiconductor lasers and optical amplifiers (SOAs) also offer nonlinearities but they differ in that they add amplified spontaneous emission (ASE). Squeezing to below the vacuum level has been demonstrated in a semiconductor laser, and gain saturation in SOAs can likewise reduce photon-number fluctuations to, and in some cases below, the vacuum limit. Here, we demonstrate that Rabi oscillations in room-temperature quantum-dot SOAs, induced by short resonant pulses, cause cyclical noise modification that repeat with every change of 2pi in pulse area, corresponding to a fourfold increase in excitation pulse energy. Homodyne measurements reveal in those cases elliptical Wigner functions corresponding to squeezed thermal states and in certain regimes, the state is squeezed to below the vacuum level. At other pulse areas, the Wigner functions are circular representing thermal coherent states. This periodic behavior persists over two orders of magnitude in input pulse energy, spanning several 2pi cycles. Under specific bias and excitation conditions, we further observe a non-Gaussian Wigner function featuring two bright lobes. Although its precise nature remains unresolved, this structure may be consistent with a Schrodinger cat - like state whose accompanying negativity is suppressed due to an approximately 10 dB optical output loss. Notably, the emergence of this non-Gaussian state is itself periodic in excitation pulse energy.

cond-mat.mes-hall↗
arXiv2024

Effects of dislocation filtering layers on optical properties of third telecom window emitting InAs/InGaAlAs quantum dots grown on silicon substrates

Integrating light emitters based on III-V materials with silicon-based electronics is crucial for further increase in data transfer rates in communication systems since the indirect bandgap of silicon prevents its direct use as a light source. We investigate here InAs/InGaAlAs quantum dot (QD) structures grown directly on 5° off-cut Si substrate and emitting light at 1.5 micrometers, compatible with established telecom platform. Using different dislocation defects filtering layers, exploiting strained superlattices and supplementary QD layers, we mitigate the effects of lattice constant and thermal expansion mismatches between III-V materials and Si during growth. Complementary optical spectroscopy techniques, i.e. photoreflectance and temperature-, time- and polarization- resolved photoluminescence, allow us to determine the optical quality and application potential of the obtained structures by comparing them to a reference sample -- state-of-the-art QDs grown on InP. Experimental findings are supported by calculations of excitonic states and optical transitions by combining multiband k.p and configuration-interaction methods. We show that our design of structures prevents the generation of a considerable density of defects, as intended. The emission of Si-based structures appears to be much broader than for the reference dots, due to the creation of different QD populations which might be a disadvantage in particular laser applications, however, could be favourable for others, e.g. in broadly tunable devices, sensors, or optical amplifiers. Eventually, we identify the overall most promising combination of defect filtering layers, discuss its advantages and limitations, and prospects for further improvements.

cond-mat.mes-hall↗
arXiv2017

Ramsey fringes in a room temperature quantum dot semiconductor optical amplifier

The ability to induce, observe and control quantum coherent interactions in room temperature, electrically driven optoelectronic devices is of outmost significance for advancing quantum science and engineering towards practical applications. We demonstrate here a quantum interference phenomena, Ramsey fringes, in an inhomogeneously broadened InAs/InP quantum dot (QD) ensemble in the form of a 1.5 mm long optical amplifier operating at room temperature. Observation of Ramsey fringes in semiconductor QD was previously achieved only at cryogenic temperatures and only in isolated single dot systems. A high-resolution pump probe scheme where both pulses are characterized by cross frequency resolved optical gating (X-FROG) reveals a clear oscillatory behavior both in the amplitude and the instantaneous frequency of the probe pulse with a period that equals one optical cycle at operational wavelength. Using nominal input delays of 600 to 900 fs and scanning the separation around each delay in 1 fs steps, we map the evolution of the material de-coherence and extract a coherence time. Moreover we notice a unique phenomenon, which can not be observed in single dot systems, that the temporal position of the output probe pulse also oscillates with the same periodicity but with a quarter cycle delay relative to the intensity variations. This delay is the time domain manifestation of coupling between the real and imaginary parts of the complex susceptibility.

quant-ph↗