arXiv subjects

Mathis Turgeon-Roy

Publications and source records attributed to Mathis Turgeon-Roy.

4 recordsLinked to original sources

arXiv2026

One year in a forest: Analyzing the challenges of autonomous navigation in subarctic environments

Subarctic regions have the potential to see increased deployment of autonomous robots in applications including forestry, mining, and environmental monitoring. In these conditions, an autonomous system's reliance on GNSS or cloud computing is precarious due to dense tree canopies and atmospheric attenuation, necessitating onboard sensing and data processing. However, established exteroceptive modalities, including cameras, lidars, and radars, are typically evaluated in structured urban settings or in environments that lack significant seasonal variations. To address this, we present a field report on a year-long deployment of a mobile robot in a subarctic boreal forest. We evaluate 64 km of data using nine odometry, localization, and mapping methods and assess their performance across seasonal changes. The performed experiments suggest that the environment changes significantly hinder the performance of state-of-the-art techniques, which show increased fragility when subject to conditions characterized by self-similar scenes or tall snowbanks. Additionally, complex Simultaneous Localization and Mapping (SLAM) algorithms offer limited accuracy gains over a proprioceptive baseline while significantly increasing system fragility. Furthermore, by correlating the position drift with features and confidence weight distribution, we show that visual-based SLAM methods are particularly affected by the seasonal changes. Additionally, we investigate the task of cross-season localization in a prior map. While lidar-based methods successfully completed localization runs between seasons, radar and visual methods are prone to failure due to a few matching features between runs, even within the same season. Finally, we detail the challenges and lessons learned from this year-long trial, including a multi-season Teach and Repeat (T&R) evaluation using both radar and lidar-based pipelines.

cs.RO↗

arXiv2026

Detectivity and bandwidth limits of cooled and uncooled light detection using nanomechanical resonators

Nanomechanical resonators (NMRs) offer a promising alternative to traditional thermal-based radiation detectors due to their immunity to electrical noise. In recent years, these sensors have reached the previously unattained theoretical detectivity limit set by the fluctuation noise of thermal photons at room temperature. Beyond this point, improvements of NMR resonators do not translate into greater detectivity, but in greater effective bandwidth. There is, however, no simple model predicting the limits of this bandwidth enhancement. Likewise, models predicting the performances of NMR-based radiation sensors under active cooling have not been derived. To address these gaps in knowledge, a key missing ingredient consists of defining the NMR optimal driven amplitude that minimizes additive frequency noise, but without performance degradation from nonlinear phenomena. We find that, in the context of NMR-based radiation sensing, this optimal amplitude ($a_\mathrm{opt}$) is dramatically different than the commonly assumed critical amplitude ($a_\mathrm{c}$) that defines the onset of non-linear phenomena in nanomechanical resonators. Our proposed model for this optimal amplitude allows us to quantify the maximum bandwidth enhancement in NMR-based radiation sensors. We also derive simple equations predicting the maximum detectivity in cryogenically cooled sensors. Finally, combining these two models allows us to define new universal performance limits. This unveils important general conclusions on the ideal geometry of NMR radiation sensors. We find that thermomechanically-limited sensors should be as thin and extended as possible. In contrast, readout-limited sensors should also be thin, but should be just large enough to make radiation heat transfer dominant compared to conduction.

physics.ins-det↗

arXiv2025

Laser micromachining of arbitrarily complex and overhang-free SiN nanomechanical resonators

Research on silicon nitride (SiN) nanomechanical resonators produces an exceptionally rich variety of resonator geometries, for which there is currently no available rapid prototyping solution. Experimental advances in nanobeam, trampoline, phononic bandgap, and soft-clamping structures all rely on conventional nanofabrication involving e-beam or photolithography, followed by various etching steps. These techniques are typically time-consuming, relatively inflexible, and often result in spurious residual SiN overhang that can degrade mechanical quality factors. In contrast, recent work has shown that simple resonant structures, such as nanobeams, can be prototyped by direct laser ablation of free-standing SiN membranes using a spatially distributed sequence of microholes that limits stress concentration. However, these early demonstrations were restricted to basic shapes, created by manually combining ablation routines for circles and straight lines. Here, we demonstrate the fabrication of arbitrarily complex geometries using an open-source software toolset--released with this publication--that automatically generates laser-ablated hole sequences directly from standard semiconductor layout files (i.e., GDSII). The software includes a layout alignment tool that compensates for the membrane orientation and dimensional variations, limiting material overhang to ~2 um. Using this toolset, we fabricate several resonator geometries, each in under 1 hour, two of which are exhaustively characterized as candidate structures for high-performance radiation sensing. The measured quality factors of these structures closely match finite element simulations and reach values up to 3.7 x 10^6. From these measurements, we extract material quality factors above 3700, which is on par with low-stress SiN unablated plain membranes and with comparable structures produced using conventional fabrication methods.

physics.optics↗

arXiv2025

Enhanced bandwidth in radiation sensors operating at the fundamental temperature fluctuation noise limit

Temperature-based radiation detectors are an essential tool for long optical wavelengths detection even if they often suffer from important bandwidth limitations. Their responsivity, and hence their noise equivalent power (NEP), typically degrade at frequencies exceeding the cutoff set by their characteristic thermal response time ($\tau_\text{th}$), i.e., at $\omega > \tau_\text{th}^{-1}$. Here we show that this bandwidth limitation can be broken when a radiation sensor operates at its fundamental temperature fluctuation noise limit. The key enabler of this demonstration is a nanomechanical sensor in which frequency stability is limited by fundamental temperature fluctuations over an unprecedentedly large bandwidth of 54 $\text{Hz}$. In this range, the sensor performance remains within a factor 3 from its peak detectivity ($D_T^* = 7.4 \times 10^9~\mathrm{cm \cdot Hz^{1/2} W^{-1}}$) even though the thermal cutoff frequency is 30 times lower (i.e., $1/2\mathrm{\pi} \tau_\text{th} = 1.8~\text{Hz}$). We also derive and validate experimentally closed-form expression predicting maximum bandwidth enhancement in the context of nanomechanical resonators interfaced with a closed-loop frequency tracking scheme.

physics.optics↗