Jerome Extermann

University of Applied Sciences and Arts Western Switzerland · HEPIA

We conduct 3D mapping of cryogenic temperatures via a Raman-based distributed temperature sensor, employing standard telecom single-mode fibers and polarization-independent superconducting nanowire single photon detectors (SNSPDs). By coiling a test fiber around various stages of a liquid helium cooled cryostat, our device demonstrates a lower temp...

Traumatic brain injury (TBI) is caused by a wide range of physical events and can induce an even larger spectrum of short- to long-term pathophysiologies. Neuroscientists have relied on animal models to understand the relationship between mechanical damages and functional alterations of neural cells. These in vivo and animal-based in vitro models r...

The limitations of 2D microscopy constrain our ability to observe and understand tissue-wide networks that are, by nature, 3-dimensional. Optical projection tomography (OPT) enables the acquisition of large volumes (ranging from micrometres to centimetres) in various tissues. We present a multi-modal workflow for the characterization of both struct...

Camera images are ubiquitous in machine learning research. They also play a central role in the delivery of important services spanning medicine and environmental surveying. However, the application of machine learning models in these domains has been limited because of robustness concerns. A primary failure mode are performance drops due to differ...

Optical projection tomography (OPT) is a powerful tool for three-dimensional (3D) imaging of mesoscopic samples. While it is able to achieve resolution of a few tens of microns over a sample volume of several cubic centimeters, the reconstructed images often suffer from artifacts caused by inaccurate calibration. In this work, we focus on the refra...

The growth of data throughput in optical microscopy has triggered the extensive use of supervised learning (SL) models on compressed datasets for automated analysis. Investigating the effects of image compression on SL predictions is therefore pivotal to assess their reliability, especially for clinical use. We quantify the statistical distortions...

We present a Raman distributed temperature sensor based on standard telecom single mode fibers and efficient polarization-independent superconducting nanowire single photon detectors. Our device shows 3 cm and 1.5 °C resolution on a 5 m fiber upon one minute integration. We show that spatial resolution is limited by the laser pulse width and not by...

Optical Projection Tomography (OPT) is a powerful tool for 3D imaging of mesoscopic samples, thus of great importance to image whole organs for the study of various disease models in life sciences. OPT is able to achieve resolution at a few tens of microns over a large sample volume of several cubic centimeters. However, the reconstructed OPT image...

The growth of data throughput in optical microscopy has triggered the extensive use of supervised learning (SL) models on compressed datasets for automated analysis. Investigating the effects of image compression on SL predictions is therefore pivotal to assess their reliability, especially for clinical use.We quantify the statistical distortions i...

Optical projection tomography (OPT) is a powerful tool for three-dimensional imaging of mesoscopic biological samples with great use for biomedical phenotyping studies. We present a fluorescent OPT platform that enables direct visualization of biological specimens and processes at a centimeter scale with high spatial resolution, as well as fast dat...

The impressive growth of data throughput in optical microscopy has triggered a widespread use of supervised learning (SL) models running on compressed image datasets for efficient automated analysis. However, since lossy image compression risks to produce unpredictable artifacts, quantifying the effect of data compression on SL applications is of p...

Extended-focus optical coherence tomography (xf-OCT) is a variant of optical coherence tomography (OCT) wherein the illumination and/or detection modes are engineered to provide a constant diffractionless lateral resolution over an extended depth of field (typically 3 to 10 × the Rayleigh range). xf-OCT systems operating at 800 nm have been devised...

Optical coherence microscopy (OCM) is an interferometric technique providing 3D images of biological samples with micrometric resolution and penetration depth of several hundreds of micrometers. OCM differs from optical coherence tomography (OCT) in that it uses a high numerical aperture (NA) objective to achieve high lateral resolution. However, t...

In recent years, three-dimensional mesoscopic imaging has gained significant importance in life sciences for fundamental studies at the whole-organ level. In this manuscript, we present an optical projection tomography (OPT) method designed for imaging of the intact mouse brain. The system features an isotropic resolution of ~50 µm and an acquisiti...

We present a novel extended-focus optical coherence microscope (OCM) attaining 0.7 μm axial and 0.4 μm lateral resolution maintained over a depth of 40 μm, while preserving the advantages of Fourier domain OCM. Our system uses an ultra-broad spectrum from a supercontinuum laser source. As the spectrum spans from near-infrared to visible wavelengths...

We report a bioinspired multifunctional albumin derived polypeptide coating comprising grafted poly(ethylene oxide) chains, multiple copies of the HIV TAT derived peptide enabling cellular uptake as well as mitochondria targeting triphenyl-phosphonium (TPP) groups. Exploring these polypeptide copolymers for passivating gold nanoparticles (Au NPs) y...

We present a 3D time-lapse imaging method for monitoring mitochondrial dynamics in living HeLa cells based on photothermal optical coherence microscopy and using novel surface functionalization of gold nanoparticles. The biocompatible protein-based biopolymer coating contains multiple functional groups which impart better cellular uptake and mitoch...

Functional magnetic resonance (fMRI) imaging is the current gold-standard in neuroimaging. fMRI exploits local changes in blood oxygenation to map neuronal activity over the entire brain. However, its spatial resolution is currently limited to a few hundreds of microns. Here we use extended-focus optical coherence microscopy (xfOCM) to quantitative...

In diabetes, pancreatic β-cells play a key role. These cells are clustered within structures called islets of Langerhans inside the pancreas and produce insulin, which is directly secreted into the blood stream. The dense vascularization of islets of Langerhans is critical for maintaining a proper regulation of blood glucose homeostasis and is know...

Magnetic Resonance Imaging has revolutionised our understanding of brain function through its ability to image human cerebral structures non-invasively over the entire brain. By exploiting the different magnetic properties of oxygenated and deoxygenated blood, functional MRI can indirectly map areas undergoing neural activation. Alongside the devel...

The photothermal optical lock-in optical coherence microscope (poli-OCM) introduced molecular specificity to OCM imaging, which is conventionally, a label-free technique. Here we achieve three-dimensional live cell and mitochondria specific imaging using ~4nm protein-functionalized gold nanoparticles (AuNPs). These nanoparticles do not photobleach...

Aims/hypothesis: It is generally accepted that structural and functional quantitative imaging of individual islets would be beneficial to elucidate the pathogenesis of type 1 diabetes. We here introduce functional optical coherence imaging (FOCI) for fast, label-free monitoring of beta cell destruction and associated alterations of islet vasculari...

In this visualized experiment, protocol details are provided for in vitro labeling of human embryonic stem cells (hESC) with second harmonic generation nanoparticles (HNPs). The latter are a new family of probes recently introduced for labeling biological samples for multi-photon imaging. HNPs are capable of doubling the frequency of excitation lig...

We review optical coherence microscopy and present selected structural and functional imaging applications ranging from diabetes to brain imaging, including new concepts for cell imaging with an emphasis on the underlying optical concepts.

We show that the coherent manipulation of molecular wavepackets in the excited states of trp-containing dipeptides allows efficient discrimination among them. Optimal dynamic discrimination fails, however, for some dipeptide couples. When considering the limited spectral resources at play (3 nm bandwidth at 266 nm), we discuss the concept of discri...

Optimal Dynamic Discrimination based on the phase-shaping of deep ultraviolet femtosecond pulses was applied to selectively modulate the time-resolved fluorescence depletion of pairs of tryptophan-containing dipeptides. Our results indicate that phase-sensitive excitation allows their differential identification, beyond the limits of linear and tim...

Nonlinear optical nanocrystals have been recently introduced as a promising alternative to fluorescent probes for multiphoton microscopy. We present for the first time a complete survey of the properties of five nanomaterials (KNbO3, LiNbO3, BaTiO3, KTP, and ZnO), describing their preparation and stabilization and providing quantitative estimations...

Label-free selective discrimination of spectrally similar biomolecules, such as peptides and proteins using Optimal Control strategies is a challenge in a variety of practical applications such as label-free fluorescence imaging and protein identification. The principle of Optimal Control is based on the fact that a suitably shaped laser field can...

Potassium niobate nonlinear nanoparticles are used for the first time to monitor the evolution of embryonic stem cells (ESC) by second harmonic microscopy. These particles feature the complete absence of photo-bleaching and unlimited excitation wavelength flexibility. The potential of this approach is made evident for tissue-regeneration studies an...

Nonlinear optical nanocrystals have been recently introduced as a promising alternative to fluorescent probes for multiphoton microscopy. We present for the first time a complete survey of the properties of five nanomaterials (KNbO(3), LiNbO(3), BaTiO(3), KTP, and ZnO), describing their preparation and stabilization and providing quantitative estim...

Hyper Rayleigh scattering (HRS) and second harmonic (SH) microscopy were used to study the second order nonlinear optical response of ZnO and BaTiO3 nanocrystals, which have been recently proposed as new markers for bioimaging. HRS, combined with dynamic light scattering, was first used to retrieve hyperpolarizabilities and nonlinear coefficients o...

We present an in-detail description of the design, simulation, fabrication, and packaging of a linear micromirror array specifically designed for temporal pulse shaping of ultrashort laser pulses. The innovative features of this device include a novel comb-drive actuator allowing both piston and tilt motion for phase- and amplitude-shaping, and an...

The activity of the GAP-Biophotonics research group at the University of Geneva in the field of coherent control for discriminating similar biomolecules, such as flavins, proteins and DNA bases, is presented and future developments are discussed.

We describe the performance of a reflective pulse-shaper based on a Micro-ElectroMechanical System (MEMS) linear mirror array. It represents a substantial upgrade of a preceding release [Opt. Lett. 35, 3102 (2010)] as it allows simultaneous piston and tilt mirror motion, allowing both phase- and binary amplitude-shaping with no wavelength restricti...

Shaping light with microtechnology components has been possible for many years. The Texas Instruments digital micromirror device (DMD) and all types of adaptive optics systems are very sophisticated tools, well established and widely used. Here we present, however, two very dedicated systems, where one is an extremely simple MEMS-based tunable diff...

We demonstrate the excitation of second harmonic radiation of noncentrosymmetric nanoparticles dispersed on a planar optical waveguide by the evanescent field of the guided mode. Polarization imaging reveals information on the orientation of the crystal axis of individual nanoparticles. Interference patterns generated from adjacent particles at the...

We demonstrate the capabilities of a new optical microelectromechanical systems device that we specifically developed for broadband femtosecond pulse shaping. It consists of a one-dimensional array of 100 independently addressable, high-aspect-ratio micromirrors with up to 3 μm stroke. We apply linear and quadratic phase modulations demonstrating t...

We report our progress and the first optical application on the high-aspect ratio micromirror array for UV-NIR femtosecond (fs) broadband pulse shaping. It is a bulk-micromachined device. capable of individually addressing 100 mirrors with a stroke of up to 3 μm using vertical comb drives in a novel. symmetrical double-spring design. The device was...

We show the first results of a linear 100-micromirror array capable of modulating the phase and amplitude of the spectral components of femtosecond lasers. Using MEMS-based reflective systems has the advantage of utilizing coatings tailored to the laser wavelength range. The innovative features of our device include a novel rotational, vertical com...

The ability of pellets made up of compressed iron iodate nanocrystals to frequency-double the whole visible spectrum is demonstrated. We suggest their use for complete characterization of intense ultrabroadband laser pulses.

We describe the implementation and characterization of a micro-mirror-array set-up based on Micro-Electro-Mechanical System (MEMS) technology for femtosecond pulse shaping in the deep UV. We demonstrate its capability of re-compressing spectrally broadened UV pulses with a closed-loop approach based on a genetic algorithm. A single-shot synchroniza...

We demonstrate the possibility to excite second-harmonic (SH) active Fe(IO3)3 nanocrystals with two distinct laser sources at 800 and 1550 nm, and we show, by a complementary experimental and numerical study, how the wavelength flexibility inherent to non-phase-matched SH nanoparticles can be efficiently exploited to increase imaging penetration de...

There are many potential applications for MEMS micromirror devices for femtosecond pulse shaping applications. Their broadband reflectivity gives them an advantage in comparison to devices such as liquid crystal- and acousto-optical modulators because of the possibility to directly shape UV pulses in the range 250 - 400 nm, and thus address UV-abso...

We are developing a linear array of micromirrors designed for optical, femtosecond laser pulse shaping. It is a bulkmicromachined device, capable of retarding or diminishing certain laser frequencies in order to perform phase and amplitude modulation within a frequency band spanning the UV to the near-infrared. The design consists of a linear array...

We are fabricating a bulk-micromachined micromirror device for laser pulse shaping applications on femtosecond time scales. An array of micromirrors is used to individually retard or diminish certain laser frequencies spanning from the UV to the near-infrared. The individual mirrors are fixed by two springs on either side and can be tilted (amplitu...

We present a technique to characterize ultrashort pulses at the focal plane of a high numerical aperture objective with unprecedented spatial resolution, by performing a FROG measurement with a single nanocrystal as nonlinear medium. This approach can be extended to develop novel phase-sensitive techniques in laser scanning microscopy, probing the...

We present a technique to characterize ultrashort pulses at the focal plane of a high numerical aperture objective with unprecedented spatial resolution, by performing a FROG measurement with a single nanocrystal as nonlinear medium. This approach can be extended to develop novel phase-sensitive techniques in laser scanning microscopy, probing the...

We show how an ultrafast pump-pump excitation induces strong fluorescence depletion in biological samples, such as bacteria-containing droplets, in contrast with fluorescent interferents, such as polycyclic aromatic compounds, despite similar spectroscopic properties. Application to the optical remote discrimination of biotic versus non-biotic part...

Distortions of ultrashort laser pulses propagating through turbulence are investigated both experimentally and numerically. As expected, a strong correlation is found between temporal distortions and local intensity on the speckle pattern. We suggest that the localization of distortions in low-intensity regions may favor remote control strategies b...

We present the most powerful white light femtosecond Lidar experiment to date using a 30J-30TW laser. We also discuss the applicability of coherent control to femtosecond Lidar experiments, in order to identify bioagents in air.

We have applied a multiobjective genetic algorithm to the optimization of multiphoton-excited fluorescence. Our study shows the advantages that this approach can offer to experiments based on adaptive shaping of femtosecond pulses. The algorithm outperforms single-objective optimizations, being totally independent from the bias of user defined para...

The paper reports on the investigation of the nonlinear optical properties of nanosized grains of Fe(IO3)3, recently synthesized with a simple and inexpensive process. The measurements have been carried out using a Ti:sapphire femtosecond oscillator coupled to an inverse microscope modified to detect the polarization dependence of the signal. It is...

Filamentation, which arises in the propagation of ultrashort laser pulses when the defocusing on the generated plasma dynamically balances the Kerr self-focusing, is now well described on both the laboratory scale (millijoules to tens of millijoules, meters to tens of meters) and the atmospheric scale (hundreds of millijoules, hundreds of meters to...

We have investigated nanocrystals of Fe(IO3)3 by polarization-sensitive second harmonic generation (SHG) microscopy. As the nonlinear optical properties of this material were only poorly characterized, we have first determined the relative values of the elements of its second-order susceptibility tensor, by the global fitting of the polarization-re...

We present a numerical analysis to simulate the response of a spherical resonant gravitational wave detector and to compute its sensitivity. Under the assumption of optimal filtering, we work out the sensitivity curve for a sphere first taking into account only a single transducer, and then using a coherent analysis of the whole set of transducers....

Ultrahigh power laser pulses delivered by the Alisé beamline (26 J, 32 TW pulses) have been sent vertically into the atmosphere. The highly nonlinear propagation of the beam in the air gives rise to more than 400 self-guided filaments. This extremely powerful bundle of laser filaments generates a supercontinuum propagating up to the stratosphere, b...

We present a numerical analysis to simulate the response of a spherical resonant gravitational wave detector and to compute its sensitivity. We compute both the sensitivity of each different transducers and the sensitivity obtain from a coherent analysis of the whole set of transducers. We use our model to work out the transfer function and the str...

We report on the first results of the highest power Lidar system (25 J, 45 TW) until now. Its capabilities correspond to one order of magnitude higher peak power and 100 times more energy than the Teramobile. At these extreme power levels it is a particular challenge to understand laser propagation and the potential use of it. The filaments density...