arXiv subjects

Konstantinos Papatryfonos

Publications and source records attributed to Konstantinos Papatryfonos.

9 recordsLinked to original sources

arXiv2025

Optical Waveguide-Pair Design for CMOS-Compatible Hybrid III-V-on-Silicon Quantum Dot Lasers

The development of compact, energy-efficient integrated lasers operating at 1.3 um remains a critical focus in silicon photonics, essential for advancing data communications and optical interconnect technologies. This paper presents a numerical study of distributed Bragg reflector (DBR) hybrid III-V-on-silicon lasers, analyzing design trade-offs and optimization strategies based on supermode theory. The III-V section of the design incorporates InAs/(Al)GaAs quantum dots (QDs), which offer improved temperature insensitivity at the cost of more complex III-V/Si optical coupling, due to the high refractive index of (Al)GaAs. Consequently, many current laser designs rely on silicon waveguides with a thickness exceeding 220 nm, which helps coupling but limits their compatibility with standard CMOS technologies. To address this challenge, we perform detailed simulations focusing on 220-nm-thick silicon waveguides. We first examine how the mode profiles jointly depend on the silicon waveguide dimensions and the geometry and composition of the III-V stack. Based on this analysis, we propose a novel epitaxial design that enables effective III-V/Si coupling, with the optical mode strongly confined within the III-V waveguide in the gain section and efficiently transferred to the silicon waveguide in the passive sections. Moreover, the final design is shown to be robust to fabrication-induced deviations from nominal parameters.

physics.optics↗

arXiv2025

Proposed experiments for detecting contextual hidden variables

We propose two quantum experiments - modified Bell tests - that could detect contextual hidden variables underlying quantum mechanics. The experiments are inspired by hydrodynamic pilot-wave systems that mimic a wide range of quantum effects and exhibit a classical analog of contextuality. To justify the experiments, we show that contextual hidden variables are 'physics as usual' if a unification between quantum mechanics and general relativity is possible. Accordingly, contextual theories can bypass Bell's theorem in a way that is both local and non-conspiratorial. We end with a note on the relevance of exploratory experiments in the foundations of quantum physics.

quant-ph↗

arXiv2025

Low-Defect Quantum Dot Lasers Directly Grown on Silicon Exhibiting Low Threshold Current and High Output Power at Elevated Temperatures

The direct growth of III-V materials on silicon is a key enabler for developing monolithically integrated lasers, offering substantial potential for ultra-dense photonic integration in vital communications and computing technologies. However, the III-V/Si lattice and thermal expansion mismatch pose significant hurdles, leading to defects that degrade lasing performance. This study overcomes this challenge, demonstrating InAs/GaAs-on-Si lasers that perform on par with top-tier lasers on native GaAs substrates. This is achieved through a newly developed epitaxial approach comprising a series of rigorously optimised growth strategies. Atomic-resolution scanning tunnelling microscopy and spectroscopy experiments reveal exceptional material quality in the active region, and elucidate the impact of each growth strategy on defect dynamics. The optimised III-V-on-silicon ridge-waveguide lasers demonstrate a continuous-wave threshold current as low as 6 mA and high-temperature operation reaching 165 °C. At 80 °C, critical for data centre applications, they maintain a 12-mA threshold and 35 mW output power. Furthermore, lasers fabricated on both Si and GaAs substrates using identical processes exhibit virtually identical average threshold current. By eliminating the performance limitations associated with the GaAs/Si mismatch, this study paves the way for robust and high-density integration of a broad spectrum of critical III-V photonic technologies into the silicon ecosystem.

cond-mat.mtrl-sci↗

arXiv2024

Superradiant droplet emission from a single hydrodynamic cavity near a reflective boundary

Recent advances in manipulating droplet emissions from a thin vibrating fluid using submerged cavities, have introduced an innovative platform for generating hydrodynamic analogs of quantum and optical systems. This platform unlocks unique features not found in traditional pilot-wave hydrodynamics, inviting further exploration across varied physical settings to fully unravel its potential and limitations as a quantum analog. In this study, we explore how the recently reported phenomenon of hydrodynamic superradiance is affected when a single hydrodynamic cavity is taken to interact with a submerged reflective barrier. Our experimental findings reveal that the presence of a barrier near a cavity enhances its droplet emission rate, emulating the effect of a second cavity positioned at twice the distance. Moreover, the system exhibits a sinusoidal modulation of the emission rate as a function of the distance between the cavity and its mirror image, echoing the characteristic superradiance signature observed in optical systems. These findings broaden our understanding of wave-particle duality in hydrodynamic quantum analogs and suggest new pathways for replicating quantum behaviors in macroscopic systems.

physics.flu-dyn↗

arXiv2023

Effects of surface roughness and top layer thickness on the performance of Fabry-Perot cavities and responsive open resonators based on distributed Bragg reflectors

Optical and acoustic resonators based on distributed Bragg reflectors (DBRs) hold significant potential across various domains, from lasers to quantum technologies. In ideal conditions with perfectly smooth interfaces and surfaces, the DBR resonator quality factor primarily depends on the number of DBR pairs and can be arbitrarily increased by adding more pairs. Here, we present a comprehensive analysis of the impact of top layer thickness variation and surface roughness on the performance of both Fabry-Perot and open-cavity resonators based on DBRs. Our findings illustrate that even a small, nanometer-scale surface roughness can appreciably reduce the quality factor of a given cavity. Moreover, it imposes a limitation on the maximum achievable quality factor, regardless of the number of DBR pairs. These effects hold direct relevance for practical applications, which we explore further through two case studies. In these instances, open nanoacoustic resonators serve as sensors for changes occurring in dielectric materials positioned on top of them. Our investigation underscores the importance of accounting for surface roughness in the design of both acoustic and optical DBR-based cavities, while also quantifying the critical significance of minimizing roughness during material growth and device fabrication processes.

physics.optics↗

arXiv2023

Topological Nanophononic Interface States Using High-Order Bandgaps in the One-Dimensional Su-Schrieffer-Heeger Model

Topological interface states in periodic lattices have emerged as valuable assets in the fields of electronics, photonics, and phononics, owing to their inherent robustness against disorder. Unlike electronics and photonics, the linear dispersion relation of hypersound offers an ideal framework for investigating higher-order bandgaps. In this work, we propose a design strategy for the generation and manipulation of topological nanophononic interface states within high-order bandgaps of GaAs/AlAs multilayered structures. These states arise from the band inversion of two concatenated superlattices that exhibit inverted spatial mode symmetries around the bandgap. By adjusting the thickness ratio of the unit cells in these superlattices, we are able to engineer interface states in different bandgaps, enabling the development of versatile topological devices spanning a wide frequency range. Moreover, we demonstrate that such interface states can also be generated in hybrid structures that combine two superlattices with bandgaps of different orders centered around the same frequency. These structures open up new avenues for exploring topological confinement in high-order bandgaps, providing a unique platform for unveiling and better understanding complex topological systems.

cond-mat.mes-hall↗

arXiv2023

A platform for investigating Bell correlations in pilot-wave hydrodynamics

Since its discovery in 2005, the hydrodynamic pilot-wave system has provided a concrete macroscopic realization of wave-particle duality and concomitant classical analogs of a growing list of quantum effects. The question naturally arises as to whether this system might support statistical states that violate Bell's inequality, and so yield a classical analog of quantum entanglement. We here introduce a new platform for addressing this question, a numerical model of coupled bipartite tunneling in the hydrodynamic pilot-wave system. We demonstrate that, under certain conditions, the Bell inequality is violated in a static Bell test owing to correlations induced by the wave-mediated coupling between the two subsystems. The establishment of non-factorizable states with two spatially separated classical particles introduces the possibility of novel forms of quantum-inspired classical computing.

physics.flu-dyn↗

arXiv2022

Superradiant droplet emission from parametrically excited cavities

Superradiance occurs when a collection of atoms exhibits cooperative, spontaneous emission of photons at a rate that exceeds that of its component parts. Here, we reveal a similar phenomenon in a hydrodynamic system consisting of a pair of vibrationally-excited cavities, coupled through their common wavefield, that spontaneously emit droplets via interfacial fracture. We show that the droplet emission rate of two coupled cavities is higher than the emission rate of two isolated cavities. We further show that the amplified emission rate varies sinusoidally with distance between the cavities, thus demonstrating a hydrodynamic phenomenon that captures the essential features of superradiance in optical systems.

quant-ph↗

arXiv2021

Hydrodynamic superradiance in wave-mediated cooperative tunneling

Superradiance and subradiance occur in quantum optics when the emission rate of photons from multiple atoms is enhanced and diminished, respectively, owing to interaction between neighboring atoms. We here demonstrate a classical analog thereof in a theoretical model of droplets walking on a vibrating bath. Two droplets are confined to identical two-level systems, a pair of wells between which the drops may tunnel, joined by an intervening coupling cavity. The resulting classical superradiance is rationalized in terms of the system's non-Markovian, pilot-wave dynamics.

nlin.CD↗