arXiv subjects

Florin Udrea

Publications and source records attributed to Florin Udrea.

4 recordsLinked to original sources

arXiv2025

Hybrid Single-Pulse and Sawyer-Tower Method for Accurate Transistor Loss Separation in High-Frequency High-Efficiency Power Converters

Accurate measurement of transistor parasitic capacitance and its associated energy losses is critical for evaluating device performance, particularly in high-frequency and high-efficiency power conversion systems. This paper proposes a hybrid single-pulse and Sawyer-Tower test method to analyse switching characteristics of field-effect transistors (FET), which not only eliminates overlap losses but also mitigates the effects of current backflow observed in traditional double-pulse testing. Through a precise loss separation model, it enables an accurate quantification of switching losses and provides a refined understanding of device energy dissipation mechanisms. We validate the hysteresis data and loss separation results through experimental measurements on a 350-W LLC converter, which further offers deeper insights into transistor dynamic behaviour and its dependence on operating conditions. This method is applicable to a wide range of transistors, including emerging SiC and GaN devices, and serves as a valuable tool for device characterization and optimization in power electronics.

eess.SY↗

arXiv2024

High-Transmission Mid-Infrared Bandpass Filters Using Hybrid Metal-Dielectric Metasurfaces for CO2 Sensing

Mid-infrared (MIR) spectroscopy is a powerful technique employed for a variety of applications, including gas sensing, industrial inspection, astronomy, surveillance, and imaging. Thin-film narrowband interference filters, targeted to specific absorption bands of target molecules, are commonly deployed for cost-effective MIR sensing systems. These devices require complex and time-consuming fabrication processes. Also, their customization on the micro-scale for emerging miniaturized applications is challenging. Plasmonic nanostructure arrays operating in reflection and transmission modes have been developed for MIR. However, they experience undesirable characteristics, such as broad spectra and low reflection/transmission efficiencies. All-dielectric metasurfaces have low intrinsic losses and have emerged as a substitute for plasmonic metasurfaces in MIR spectroscopy. Nevertheless, they typically operate only in reflection mode. In this work, we present a hybrid metal-dielectric metasurface for MIR spectroscopy operating in transmission mode. The metasurface is composed of germanium (Ge) atop aluminum (Al) cylinders, and we show that the transmission response arises because of the hybridization of modes arising from the Ge and the Al structures. The presented metasurface has a high transmission efficiency of 80 % at $λ= 2.6\ μ\text{m}$, and a narrow full-width-at-half-maximum of $0.4\ μ\text{m}$. We show numerical simulations, successful fabrication using a straightforward fabrication method, and deployment as the in-line optical filter in a CO$_2$ gas detection with a limit of detection of ~0.04% (a few hundred ppm). Our work demonstrates the potential for hybrid metasurfaces as in-line gas sensing optical filters in MIR spectroscopy.

physics.optics↗

arXiv2000

Quantum Computation with Ballistic Electrons

We describe a solid state implementation of a quantum computer using ballistic single electrons as flying qubits in 1D nanowires. We show how to implement all the steps required for universal quantum computation: preparation of the initial state, measurement of the final state and a universal set of quantum gates. An important advantage of this model is the fact that we do not need ultrafast optoelectronics for gate operations. We use cold programming (or pre-programming), i.e., the gates are set before launching the electrons; all programming can be done using static electric fields only.

quant-ph↗

arXiv1999

Ballistic Single-Electron Quputer

We propose a new solid state implementation of a quantum computer (quputer) using ballistic single electrons as flying qubits in 1D nanowires. We use a single electron pump (SEP) to prepare the initial state and a single electron transistor (SET) to measure the final state. Single qubit gates are implemented using quantum dots as phase shifters and electron waveguide couplers as beam splitters. A Coulomb coupler acts as a 2-qubit gate, using a mutual phase modulation effect. Since the electron phase coherence length in GaAs/AlGaAs heterostructures is of the order of 30$μ$m, several gates (tens) can be implemented before the system decoheres.

quant-ph↗