Time-Resolved Spectroscopy (TRS) is a powerful modality for non-invasive characterization of turbid media. However, extracting optical properties, absorption μ_a and reduced scattering μ_s', from 3D stochastic measurements remains computationally expensive for real-time applications. In this paper, we propose a data-efficient, physics-informed transfer learning strategy using a Bidirectional Long Short-Term Memory (Bi-LSTM) network. By leveraging a fast deterministic solver to establish a physical prior before fine-tuning on a restricted set of 3D Monte Carlo simulations, our model successfully bridges the analytical-to-stochastic domain gap. The proposed method eliminates the systematic bias of analytical models while maintaining a competitive error with near-instantaneous inference time.

In the context of blood oxygenation assessment, pulse oximetry has become the ubiquitous substitute for the painful and impractical “blood gases” arterial puncture. It relies on the optical principle of photoplethysmography (PPG), which involves an acquisition chain that can be plagued by different sources of non-idealities. In particular, the high variability in the current-intensity response of the Light Emitting Diodes (LEDs), the variability in photodiode sensitivity, and the non-linear behaviour of both components can pose serious challenges to the accuracy of pulsed di-oxygen saturation $\boldsymbol{(} \mathbf{s p O}_{\mathbf{2}} \boldsymbol{)}$ estimation. This paper first introduces the simplified model of a complete PPG acquisition chain, before focusing more specifically on the compensation of inter-device LEDs dispersion. A real-life case study is then presented using Biosency’s Bora band, a telemonitoring device enabling long-term, wrist-based monitoring of $\mathbf{s p O}_{\mathbf{2}}$. The proposed compensation strategy for the LEDs non-linearity results in a significant reduction of the $\mathbf{s p O}_{\mathbf{2}}$ estimation Root Mean Square Error (RMSE), as well as of the inter-device bias, thereby demonstrating the effectiveness of the proposed approach at the Tx-side, while the Rx-side compensation is only outlined, and left for future validation.

Exciton dynamics play a crucial role in determining the efficiency of organic photovoltaic devices and photo-detectors. However, establishing clear correlations between molecular structure and exciton diffusion length remains a significant challenge, limiting the rational design of more efficient materials. In this study, we investigate exciton transport in thin films of a planar dumbbell-shaped electron donor composed of discotic triazatruxene end-groups and an electron-deficient central unit. These molecules self-assemble into unique bridged-columnar structures, which are known to support efficient charge transport, although their impact on exciton dynamics had not yet been explored. Using a combination of time-resolved photoluminescence (TRPL), spatially resolved TRPL, and exciton-exciton annihilation measurements, we examine how structural order influences exciton diffusion in both the columnar-nematic and crystalline phases. We show that crystallization leads to a twofold increase in exciton diffusion length, reaching values comparable to those observed in state-of-the-art non-fullerene acceptors. Although the molecules exhibit a typical Stokes shift that is not particularly favorable for F & ouml;rster energy transfer (FRET), efficient exciton transport is nonetheless achieved-enabled by long exciton lifetimes and anisotropic energy transfer within its distinctive bridged-columnar architecture. These results, supported by FRET analysis, highlight the effectiveness of the molecule's tailored dumbbell-shaped design and its ability to self-assemble into ordered structures that support both long-range exciton diffusion and efficient charge mobility.

The objective of this study is to generate random numbers using Single Photon Avalanche Diode (SPAD) native noise, specifically the Dark Count Rate (DCR). This is achieved by counting events over a fixed acquisition time window and creating a sequence of random bits using the least significant bits of the counter. A simple model was developed to evaluate the concept, which was then implemented on noisy SPADs integrated in CMOS Fully Depleted Silicon-On-Insulator (FD-SOI) technology, resulting in a compact 3D cell. The study tested the randomness quality of the measured bit sequences under various operating conditions, including voltage and temperature. The results indicate that the measured bit sequences pass successfully the NIST randomness quality tests under specific operating conditions. It is recommended to use the least significant bit and work with a sufficiently high excess voltage.

We propose a technique to suppress the noise of Trans-Impedance Amplifiers (TIAs) in an integrated streak camera for repeatable input signals. This approach requires only a minor modification to the sensor architecture, involving the addition of a single power supply connected to the column buffer of the sampling cell. The noise rejection mechanism operates independently of the system's effective bandwidth. Simulation results demonstrate a reduction in TIA noise from 5.2 mV to 0.31 mV, which corresponds to the fundamental limit imposed by thermal noise on the sampling capacitor (kTC noise). As a result, the signal-to-noise ratio improves by more than an order of magnitude, achieving over a tenfold enhancement with an acquisition time of just 20 mu s, enabled by the on-chip analog averaging feature. This noise reduction capability enables the detection of low-light signals, allowing the system to accurately measure optical pulses containing as few as 300 photoelectrons with a signal-to-noise ratio (SNR) exceeding 10 and a full width at half maximum (FWHM) of 200 ps.

This work presents the development of a 400-pixel solid-state streak camera, designed in 0.13 mu m BiCMOS technology, with a focus on enhancing the front-end architecture to push analog performance across all channels. The sensor achieves a framerate of 10 Gfps and a total sampling rate of 4 Terapixels/s, utilizing a novel integrated Streak architecture. Each of the 400 integrated photodiodes is connected to a high-performance wide-band transimpedance amplifier, delivering 92 dB of gain and 3 GHz of bandwidth, far exceeding what is reported in the current literature. While the sweep speed of 100 ps is in line with state-of-the-art systems, the exceptional front-end performance marks a significant advance. The design also incorporates a 400-point deep analog on-chip memory for burst imaging and includes a post-trigger functionality to resolve synchronization challenges during event recording.

Straylight (SL) characterization using ultrafast time of flight imaging (ToF) has been demonstrated for the testing of refractive telescopes, using a streak tube with a femtosecond laser. It was shown that individual SL contributors such as different ghost reflections and scattering features can be measured individually and identified by temporal discrimination due to the specific optical path length of each of them. This allows to analyze them individually for a better understanding of straylight properties in instruments. Recently, we have used the ToF approach to characterize a testing facility that was then used in the frame of the calibration campaign for the Narrow Angle Camera (NAC) of the Earth Return Orbiter mission. The facility itself could generate its own SL that has to be retrieved from that coming from the instrument. Due to the large facility dimensions, optical path lengths can be discriminated by using a low temporal resolution that is enabled by picosecond lasers associated to a SPAD detector. At the end, the SL coming from the facility can be reverse engineered to find its origin and either removed by facility adaptation or by processing.

The integration of Single-Photon Avalanche Diodes (SPADs) in CMOS Fully Depleted Silicon-On-Insulator (FD-SOI) technology under a buried oxide (BOX) layer and a silicon film containing transistors makes it possible to realize a 3D SPAD at the chip level. In our study, a nanostructurated layer created by an optimized arrangement of Shallow Trench Isolation (STI) above the photosensitive zone generates constructive interferences and consequently an increase in the light sensitivity in the frontside illumination. A simulation methodology is presented that couples electrical and optical data in order to optimize the STI trenches (size and period) and to estimate the Photon Detection Probability (PDP) gain. Then, a test chip was designed, manufactured, and characterized, demonstrating the PDP improvement due to the STI nanostructuring while maintaining a comparable Dark Count Rate (DCR).

A digital asynchronous logic is proposed as a generic matrix readout for Monolithic active pixel sensors. The architecture is implemented for pixel pitch ranging from 18 to 30 mu m. Post-layout simulations with realistic hit shapes and rates up to 200 MHz/cm2 2 show that time stamping at the 20 ns level can be achieved for a digital power cost below 10 mW/cm2. 2 .

Single photon avalanche diodes (SPADs) are crucial for Industry 4.0 advancements, especially in the design of LIght Detection And Ranging (LIDAR) sensors. A compact model is needed to accurately describe their transient behavior. This article presents a lumped model approach that divides the device into different regions. The model accurately emulates the behavior of reach-through SPAD photodiodes by dividing them into high electric field multiplication and low electric field absorption regions. The absorption region can be further subdivided to create multiple possible photon impact points, resulting in precise jitter modeling. This approach enables adaptable and unified SPAD modeling for different avalanche diode architectures. Experimental data confirm the accuracy of the model, and the characterization technique developed highlights the stochastic nature of the device.

Objective: present transcutaneous carbon dioxide (CO2)—tcpCO2—monitors suffer from limitations which hamper their widespread use, and call for a new tcpCO2 measurement technique. However, the progress in this area is hindered by the lack of knowledge in transcutaneous CO2 diffusion. To address this knowledge gap, this study focuses on investigating the influence of skin temperature on two key skin properties: CO2 permeability and skin blood flow.Methods: a monocentric prospective exploratory study including 40 healthy adults was undertaken. Each subject experienced a 90 min visit split into five 18 min sessions at different skin temperatures—Non-Heated (NH), 35, 38, 41, and 44°C. At each temperature, custom sensors measured transcutaneous CO2 conductivity and exhalation rate at the arm and wrist, while Laser Doppler Flowmetry (LDF) assessed skin blood flow at the arm.Results: the three studied metrics sharply increased with rising skin temperature. Mean values increased from the NH situation up to 44°C from 4.03 up to 8.88 and from 2.94 up to 8.11 m·s−1 for skin conductivity, and from 80.4 up to 177.5 and from 58.7 up to 162.3 cm3·m−2·h−1 for exhalation rate at the arm and wrist, respectively. Likewise, skin blood flow increased elevenfold for the same temperature increase. Of note, all metrics already augmented significantly in the 35–38°C skin temperature range, which may be reached without active heating—i.e. only using a warm clothing.Conclusion: these results are extremely encouraging for the development of next-generation tcpCO2 sensors. Indeed, the moderate increase (× 2) in skin conductivity from NH to 44°C tends to indicate that heating the skin is not critical from a response time point of view, i.e. little to no skin heating would only result in a doubled sensor response time in the worst case, compared to a maximal heating at 44°C. Crucially, a skin temperature within the 35–38°C range already sharply increases the skin blood flow, suggesting that tcpCO2 correlates well with the arterial paCO2 even at such low skin temperatures. These two conclusions further strengthen the viability of non-heated tcpCO2 sensors, thereby paving the way for the development of wearable transcutaneous capnometers.

Stray light (SL) has emerged as a primary limiting factor for space telescopes. Pre-launch testing is essential for validating performance and identifying potential issues. However, traditional methods do not enable the decomposition and identification of individual SL contributors. Consequently, when problems arise, resolving them often involves a cumbersome and risky trial-and-error approach. The time-of-flight (ToF) method was recently introduced, employing a pulsed laser source and ultrafast sensor to characterize individual SL contributors. A proof of concept was achieved using a simple three-lens system. In this paper, we apply the ToF method to a real space optical system: the spare model of the CoRoT baffle. We successfully measured individual SL contributors over a dynamic range of 10−11, identifying direct scattering on vane edges and two-step scattering paths. Our results provide a performance breakdown, differentiating intrinsic baffle SL from contributions arising from experimental conditions. Notably, the ToF method allowed us to discriminate air scattering, eliminating the need for expensive vacuum testing. The ToF provides unparallel insights, including defects identification. For instance, we identified the presence of localized dust particles causing significant SL. These results confirm the utility of the ToF method even for the most challenging space systems.

Among the many applications of carbon dioxide (CO 2 ) sensing, transcutaneous CO 2 monitoring has gathered recent attention due to the urge to develop a new generation of clinical-grade monitors. To this end, a Dual Lifetime Referencing (DLR) sensing scheme may be used in combination with a CO 2 -responsive fluorescent thin film. In this work, we present an in vitro validation of previously-published theoretical developments on the reachable accuracy of a DLR sensing scheme under different noise conditions. A CO 2 -sensitive film was developed, consisting in a polymer matrix embedding the 1-hydroxy-pyrene-3,6,8-trisulfonate (HPTS) and tris(4,7-diphenyl-1,10 phenanthro-line) ruthenium (II) dichloride (Ru-dpp) fluorophores. The latter film was probed at 450 nm by mean of a Light Emitting Diode (LED) / photodiode pair. Our results indicate a good agreement between theory and practice. However, further research is needed in order to miniaturize the measurement setup and package it into a more user-friendly contraption before in vivo experiments can be conducted.

Accurate phase extraction from sinusoidal signals is a crucial task in various signal processing applications. While prior research predominantly addresses the case of asynchronous sampling with unknown signal frequency, this study focuses on the more specific situation where synchronous sampling is possible, and the signal's frequency is known. In this framework, a comprehensive analysis of phase estimation accuracy in the presence of both additive and phase noises is presented. A closed-form expression for the asymptotic Probability Density Function (PDF) of the resulting phase is asymptotically efficient, converging rapidly to its Cram & egrave;r-Rao identified based on SNR, sample count (N), and noise level: (i) (SNR), (ii) linear decrease with the square roots of N and SNR at the impact of sample count, additive noise, and phase noise on phase estimation accuracy, this work provides valuable insights for designing systems requiring precise phase extraction, such as phase-based fluorescence assays or system identification.

Cet article décrit un TD d’introduction aux architectures des microcontrôleurs réalisé avec les étudiants de Télécom Physique Strasbourg en première année du cycle de formation ingénieur (BAC + 3) en spécialisation « Informatique et Réseaux ». Il vise à introduire les concepts fondamentaux de l’architecture des microcontrôleurs sur un exemple concret, en l’occurrence la réalisation d’un microcontrôleur élémentaire à l’aide du logiciel LOGISIM. Les travaux dirigés se déroulent sur 4 séances au cours desquelles les étudiants mettent en œuvre un microcontrôleur 6 bits qu’ils devront ensuite programmer en assembleur.

This work presents a new burst mode CMOS image sensor in 0.35 mu m SiGe BiCMOS technology that can achieve a pixel rate of 1 TS/s. The sensor employs a novel integrated Streak architecture that includes a vector of 200 integrated photodiodes, each connected to a wideband transimpedance amplifier, and a 200 points deep analogue on-chip memory for burst imaging. Placing the pixel electronics next to the photodector results in a high fill factor of 84 %. The circuit has a closed loop delay generator that allows sampling speeds from 50 mu s to 200 ps, resulting in the largest range recorded for a monolithic CMOS sensor to date. The sensor features a post-trigger functionality to avoid synchronization issues during event recording. For the recording of repetitive events, the sensor has a new accumulation mode to enhance the signal to noise ratio (SNR) by reducing the bandwidth of the sample & hold circuit, thus allowing the SNR to be increased by a factor of sqrt(10) per decade. The state-of-the-art time resolution makes this sensor ideal for observing subnanosecond events. It finds applications in various fields, including fluorescence metrology, time-resolved spectroscopy, optical tomography, laser Doppler velocimetry, and detonics.