@article{pmid37112288,

title = {Enhancing Evanescent Wave Coupling of Near-Surface Waveguides with Plasmonic Nanoparticles},

author = {Jerome Lapointe and Alexandre Grégoire and Jean-Philippe Bérubé and Réal Vallée},

doi = {10.3390/s23083945},

issn = {1424-8220},

year  = {2023},

date = {2023-04-01},

journal = {Sensors (Basel)},

volume = {23},

number = {8},

abstract = {Evanescent field excitation is a powerful means to achieve a high surface-to-bulk signal ratio for bioimaging and sensing applications. However, standard evanescent wave techniques such as TIRF and SNOM require complex microscopy setups. Additionally, the precise positioning of the source relative to the analytes of interest is required, as the evanescent wave is critically distance-dependent. In this work, we present a detailed investigation of evanescent field excitation of near-surface waveguides written using femtosecond laser in glass. We studied the waveguide-to-surface distance and refractive index change to attain a high coupling efficiency between evanescent waves and organic fluorophores. First, our study demonstrated a reduction in sensing efficiency for waveguides written at their minimum distance to the surface without ablation as the refractive index contrast of the waveguide increased. While this result was anticipated, it had not been previously demonstrated in the literature. Moreover, we found that fluorescence excitation by waveguides can be enhanced using plasmonic silver nanoparticles. The nanoparticles were also organized in linear assemblies, perpendicular to the waveguide, with a wrinkled PDMS stamp technique, which resulted in an excitation enhancement of over 20 times compared to the setup without nanoparticles.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid36878977,

title = {Toward low-loss mid-infrared GaO-BaO-GeO optical fibers},

author = {Théo Guérineau and Samar Aouji and Steeve Morency and Florian Calzavara and Patrick Larochelle and Philippe Labranche and Jerome Lapointe and Sylvain Danto and Thierry Cardinal and Evelyne Fargin and Martin Bernier and Réal Vallée and Younès Messaddeq},

doi = {10.1038/s41598-023-30522-1},

issn = {2045-2322},

year  = {2023},

date = {2023-03-01},

journal = {Sci Rep},

volume = {13},

number = {1},

pages = {3697},

abstract = {The development of efficient and compact photonic systems in support of mid-infrared integrated optics is currently facing several challenges. To date, most mid-infrared glass-based devices are employing fluoride or chalcogenide glasses (FCGs). Although the commercialization of FCGs-based optical devices has rapidly grown during the last decade, their development is rather cumbersome due to either poor crystallization and hygroscopicity resilience or poor mechanical-thermal properties of the FCGs. To overcome these issues, the parallel development of heavy-metal oxide optical fiber from the barium-germanium-gallium oxide vitreous system (BGG) has revealed a promising alternative. However, over 30 years of fiber fabrication optimization, the final missing step of drawing BGG fibers with acceptable losses for meters-long active and passive optical devices had not yet been reached. In this article, we first identify the three most important factors that prevent the fabrication of low-loss BGG fibers i.e., surface quality, volumic striae and glass thermal-darkening. Each of the three factors is then addressed in setting up a protocol enabling the fabrication of low-loss optical fibers from gallium-rich BGG glass compositions. Accordingly, to the best of our knowledge, we report the lowest losses ever measured in a BGG glass fiber i.e., down to 200 dB km at 1350 nm.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid36151236,

title = {Femtosecond tunable solitons up to 4.8  µm using soliton self-frequency shift in an InF fiber},

author = {Jean-Christophe Gauthier and Michel Olivier and Pascal Paradis and Marie-Frédérique Dumas and Martin Bernier and Réal Vallée},

doi = {10.1038/s41598-022-19658-8},

issn = {2045-2322},

year  = {2022},

date = {2022-09-01},

journal = {Sci Rep},

volume = {12},

number = {1},

pages = {15898},

abstract = {A tunable ultrashort soliton pulse source reaching up to 4.8 µm is demonstrated based on a 2.8 µm femtosecond fiber laser coupled to a zirconium fluoride fiber amplifier followed by a small core indium fluoride fiber. This demonstration is extending by 300 nm the long wavelength limit previously reported with soliton self-frequency shift (SSFS) sources based on fluoride fibers. Our experimental and numerical investigation highlighted the spectral dynamics associated with the generation of highly redshifted pulses in the mid-infrared using SSFS enhanced by soliton fission. This study is intended at providing a better understanding of the potential and limitations of SSFS based tunable femtosecond fiber sources in the 3-5  µm spectral range.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid35288603,

title = {Probing the dispersive properties of optical fibers with an array of femtosecond-written fiber Bragg gratings},

author = {Tommy Boilard and Réal Vallée and Martin Bernier},

doi = {10.1038/s41598-022-08329-3},

issn = {2045-2322},

year  = {2022},

date = {2022-03-01},

journal = {Sci Rep},

volume = {12},

number = {1},

pages = {4350},

abstract = {We propose an efficient method to determine the effective refractive index of step-index optical fibers from the visible to the mid-IR and thus allowing to infer their dispersive properties over a broad spectral range. The validity of the method, based on the writing of an array of fiber Bragg gratings (FBGs) with known periods using the fs scanning phase mask technique, is first confirmed with a standard silica fiber, then applied to various fluoride glass fibers to determine their effective refractive index and dispersion over more than three octaves, i.e. from 550 to 4800 nm.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid34199235,

title = {Smartphone Screen Integrated Optical Breathalyzer},

author = {Jerome Lapointe and Hélène-Sarah Bécotte-Boutin and Stéphane Gagnon and Simon Levasseur and Philippe Labranche and Marc D'Auteuil and Manel Abdellatif and Ming-Jun Li and Réal Vallée},

doi = {10.3390/s21124076},

issn = {1424-8220},

year  = {2021},

date = {2021-06-01},

journal = {Sensors (Basel)},

volume = {21},

number = {12},

abstract = {One third of fatal car accidents and so many tragedies are due to alcohol abuse. These sad numbers could be mitigated if everyone had access to a breathalyzer anytime and anywhere. Having a breathalyzer built into a phone or wearable technology could be the way to get around reluctance to carry a separate device. With this goal, we propose an inexpensive breathalyzer that could be integrated in the screens of mobile devices. Our technology is based on the evaporation rate of the fog produced by the breath on the phone screen, which increases with increasing breath alcohol content. The device simply uses a photodiode placed on the side of the screen to measure the signature of the scattered light intensity from the phone display that is guided through the stress layer of the Gorilla glass screen. A part of the display light is coupled to the stress layer via the evanescent field induced at the edge of the breath microdroplets. We demonstrate that the intensity signature measured at the detector can be linked to blood alcohol content. We fabricated a prototype in a smartphone case powered by the phone's battery, controlled by an application installed on the smartphone, and tested it in real-world environments. Limitations and future work toward a fully operational device are discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid32351688,

title = {Nonlinear increase, invisibility, and sign inversion of a localized fs-laser-induced refractive index change in crystals and glasses},

author = {Jerome Lapointe and Jean-Philippe Bérubé and Yannick Ledemi and Albert Dupont and Vincent Fortin and Younes Messaddeq and Réal Vallée},

doi = {10.1038/s41377-020-0298-8},

issn = {2047-7538},

year  = {2020},

date = {2020-01-01},

journal = {Light Sci Appl},

volume = {9},

pages = {64},

abstract = {Multiphoton absorption via ultrafast laser focusing is the only technology that allows a three-dimensional structural modification of transparent materials. However, the magnitude of the refractive index change is rather limited, preventing the technology from being a tool of choice for the manufacture of compact photonic integrated circuits. We propose to address this issue by employing a femtosecond-laser-induced electronic band-gap shift (FLIBGS), which has an exponential impact on the refractive index change for propagating wavelengths approaching the material electronic resonance, as predicted by the Kramers-Kronig relations. Supported by theoretical calculations, based on a modified Sellmeier equation, the Tauc law, and waveguide bend loss calculations, we experimentally show that several applications could take advantage of this phenomenon. First, we demonstrate waveguide bends down to a submillimeter radius, which is of great interest for higher-density integration of fs-laser-written quantum and photonic circuits. We also demonstrate that the refractive index contrast can be switched from negative to positive, allowing direct waveguide inscription in crystals. Finally, the effect of the FLIBGS can compensate for the fs-laser-induced negative refractive index change, resulting in a zero refractive index change at specific wavelengths, paving the way for new invisibility applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid23469053,

title = {A multimodal micro-optrode combining field and single unit recording, multispectral detection and photolabeling capabilities},

author = {Suzie Dufour and Guillaume Lavertu and Sophie Dufour-Beauséjour and Alexandre Juneau-Fecteau and Nicole Calakos and Martin Deschênes and Réal Vallée and Yves De Koninck},

doi = {10.1371/journal.pone.0057703},

issn = {1932-6203},

year  = {2013},

date = {2013-01-01},

journal = {PLoS One},

volume = {8},

number = {2},

pages = {e57703},

abstract = {Microelectrodes have been very instrumental and minimally invasive for in vivo functional studies from deep brain structures. However they are limited in the amount of information they provide. Here, we describe a, aluminum-coated, fibre optic-based glass microprobe with multiple electrical and optical detection capabilities while retaining tip dimensions that enable single cell measurements (diameter ≤10 µm). The probe enables optical separation from individual cells in transgenic mice expressing multiple fluorescent proteins in distinct populations of neurons within the same deep brain nucleus. It also enables color conversion of photoswitchable fluorescent proteins, which can be used for post-hoc identification of the recorded cells. While metal coating did not significantly improve the optical separation capabilities of the microprobe, the combination of metal on the outside of the probe and of a hollow core within the fiber yields a microelectrode enabling simultaneous single unit and population field potential recordings. The extended range of functionalities provided by the same microprobe thus opens several avenues for multidimensional structural and functional interrogation of single cells and their surrounding deep within the intact nervous system.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid22463025,

title = {Live animal myelin histomorphometry of the spinal cord with video-rate multimodal nonlinear microendoscopy},

author = {Erik Bélanger and Joël Crépeau and Sophie Laffray and Réal Vallée and Yves De Koninck and Daniel Côté},

doi = {10.1117/1.JBO.17.2.021107},

issn = {1560-2281},

year  = {2012},

date = {2012-02-01},

journal = {J Biomed Opt},

volume = {17},

number = {2},

pages = {021107},

abstract = {In vivo imaging of cellular dynamics can be dramatically enabling to understand the pathophysiology of nervous system diseases. To fully exploit the power of this approach, the main challenges have been to minimize invasiveness and maximize the number of concurrent optical signals that can be combined to probe the interplay between multiple cellular processes. Label-free coherent anti-Stokes Raman scattering (CARS) microscopy, for example, can be used to follow demyelination in neurodegenerative diseases or after trauma, but myelin imaging alone is not sufficient to understand the complex sequence of events that leads to the appearance of lesions in the white matter. A commercially available microendoscope is used here to achieve minimally invasive, video-rate multimodal nonlinear imaging of cellular processes in live mouse spinal cord. The system allows for simultaneous CARS imaging of myelin sheaths and two-photon excitation fluorescence microendoscopy of microglial cells and axons. Morphometric data extraction at high spatial resolution is also described, with a technique for reducing motion-related imaging artifacts. Despite its small diameter, the microendoscope enables high speed multimodal imaging over wide areas of tissue, yet at resolution sufficient to quantify subtle differences in myelin thickness and microglial motility.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21317908,

title = {A microprobe for parallel optical and electrical recordings from single neurons in vivo},

author = {Yoan LeChasseur and Suzie Dufour and Guillaume Lavertu and Cyril Bories and Martin Deschênes and Réal Vallée and Yves De Koninck},

doi = {10.1038/nmeth.1572},

issn = {1548-7105},

year  = {2011},

date = {2011-04-01},

journal = {Nat Methods},

volume = {8},

number = {4},

pages = {319--325},

abstract = {Recording electrical activity from identified neurons in intact tissue is key to understanding their role in information processing. Recent fluorescence labeling techniques have opened new possibilities to combine electrophysiological recording with optical detection of individual neurons deep in brain tissue. For this purpose we developed dual-core fiberoptics-based microprobes, with an optical core to locally excite and collect fluorescence, and an electrolyte-filled hollow core for extracellular single unit electrophysiology. This design provides microprobes with tips < 10 μm, enabling analyses with single-cell optical resolution. We demonstrate combined electrical and optical detection of single fluorescent neurons in rats and mice. We combined electrical recordings and optical Ca²(+) measurements from single thalamic relay neurons in rats, and achieved detection and activation of single channelrhodopsin-expressing neurons in Thy1::ChR2-YFP transgenic mice. The microprobe expands possibilities for in vivo electrophysiological recording, providing parallel access to single-cell optical monitoring and control.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20372572,

title = {Quantitative myelin imaging with coherent anti-Stokes Raman scattering microscopy: alleviating the excitation polarization dependence with circularly polarized laser beams},

author = {E Bélanger and S Bégin and S Laffray and Y De Koninck and R Vallée and D Côté},

doi = {10.1364/OE.17.018419},

issn = {1094-4087},

year  = {2009},

date = {2009-10-01},

journal = {Opt Express},

volume = {17},

number = {21},

pages = {18419--18432},

abstract = {The use of coherent anti-Stokes Raman scattering microscopy tuned to the lipid vibration for quantitative myelin imaging suffers from the excitation polarization dependence of this third-order nonlinear optical effect. The contrast obtained depends on the orientation of the myelin membrane, which in turn affects the morphometric parameters that can be extracted with image analysis. We show how circularly polarized laser beams can be used to avoid this complication, leading to images free of excitation polarization dependence. The technique promises to be optimal for in vivo imaging and the resulting images can be used for coherent anti-Stokes Raman scattering optical histology on native state tissue.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}