arXiv subjects

Magnus Borgström

Publications and source records attributed to Magnus Borgström.

3 recordsLinked to original sources

arXiv2026

Position-Dependent Calibration and Frequency Stability in On-Axis Optical Transduction of Vertical InP Nanowire Resonators

We present a quantitative framework for on-axis optical transduction of vertical InP nanowire resonators, correlating laser position to signal amplitude, calibration, and frequency stability. Photothermal resonance detuning is used to reconstruct the local beam intensity profile and to calibrate the photodetector signal using the thermomechanical noise. A noise model incorporating shot noise and spatial variation in substrate reflectance predicts the position-dependent Allan deviation. We find that the optimal detection position lies near the steepest intensity gradient, and that increasing laser power does not significantly improve frequency stability, because the accompanying temperature rise enhances thermomechanical noise and offsets the signal gain. These results establish design guidelines for optimizing nanowire-based sensors in on-axis optical detection schemes.

physics.app-ph↗

arXiv2023

Artificial Nanophotonic Neuron with Internal Memory for Biologically Inspired and Reservoir Network Computing

Neurons with internal memory have been proposed for biological and bio-inspired neural networks, adding interesting functionality. We propose and model a nanoscale optoelectronic neural node with charge-based time-limited memory and signal evaluation. Connectivity is achieved by weighted light signals emitted and received by the nodes. The device is based on well-developed III-V nanowire technology, which has shown high photo-conversion efficiency, low energy consumption and sub-wavelength light concentration. We create a flexible computational model of the complete artificial neural node device using experimental values for wire performance. The model can simulate combinations of nodes with different hardware derived properties and widely variable light interconnects. Using this model, we simulate the hardware implementation for two types of neural networks. First, we show that intentional variations in the memory decay time of the nodes can significantly improve the performance of a reservoir network. Second, we simulate the nanowire node implementing an anatomically constrained functioning model of the central complex network of the insect brain and find that it functions well even including variations in the node performance as would be found in realistic device fabrication. Our work demonstrates the feasibility of a concrete, variable, nanophotonic neural node with a memory. The use of variable memory time constants to open new opportunities for network performance is a general hardware derived feature and should be applicable for a broad range of implementations.

physics.app-ph↗

arXiv2020

Hot-Carrier Separation in Heterostructure Nanowires observed by Electron-Beam Induced Current

The separation of hot carriers in semiconductors is of interest for applications such as thermovoltaic photodetection and third-generation photovoltaics. Semiconductor nanowires offer several potential advantages for effective hot-carrier separation such as: a high degree of control and flexibility in heterostructure-based band engineering, increased hot-carrier temperatures compared to bulk, and a geometry well suited for local control of light absorption. Indeed, InAs nanowires with a short InP energy barrier have been observed to produce electric power under global illumination, with an open-circuit voltage exceeding the Shockley-Queisser limit. To understand this behaviour in more detail, it is necessary to maintain control over the precise location of electron-hole pair-generation in the nanowire. In this work we perform electron-beam induced current measurements with high spatial resolution, and demonstrate the role of the InP barrier in extracting energetic electrons. We interprete the results in terms of hot-carrier separation, and extract estimates of the hot carrier mean free path.

cond-mat.mes-hall↗