Dielectric multilayers can be designed and fabricated to reach large optical field enhancement when working under total internal reflection. In an objective based total internal reflection fluorescence microscopy (TIRF-M), we propose to use the resulting large field enhancement supported in such resonant coverslip to improve TIRF-M sensitivity by amplifying the collected fluorescence signal. Scattering effects due to roughness of the substrate may parasite the optical response of our designed multilayer-based component. We present here the numerical model of the roughness impact over the multilayer optical response.
This project explores optical near-field characterizations using a scattering Scanning Nearfield Optical Microscope (s-SNOM) with a monochromatic visible illumination on SiO2 dielectric thin films, elaborated by electron beam deposition onto Silicon wafers. Although the amplitude and phase resulting from the optical near-field interaction are mostly used for qualitative characterizations, this work aims to achieve direct quantitative measurements of optically transparent components. In parallel, theoretical models of electric field and reflectivity variations in the propagative regime were employed, and the results were compared to the optical near-field signal variations. Insights on the properties of optical components that can be accurately measured with s-SNOM are thus provided.
We present the optimization of dielectric multilayers (DM) for improved total internal reflection fluorescence sensitivity. The desired resonances require a design that achieves a field enhancement and an angular tolerance of the resonance in the order of the illumination divergence. We studied the effect of the imaginary part of the refractive index k of the DM top layer on the fluorescence enhancement. We established a protocol to fabricate a single layer with a controlled k and fabricated three structures of various k. We tested the concept on fluorescent beads and observed a good agreement with the predicted fluorescence enhancement.
Laser-induced contamination (LIC) degrades the performance of optical components and can result in optical losses or even laser-induced damage. LIC deposit formation limits reliable operation of high repetition rate industrial lasers. In this work, we investigate LIC growth on dielectric oxide thin films in air environment irradiated by MHz sub-ps laser at 515 nm. We study the LIC growth dynamic in dependence on thin film deposition method, thin film material and thin film thickness.
TIRF-Microscopy is widely used in cell biology to monitor dynamic biomolecular events occurring at the cell membranes. However, this technic is limited by weak fluorescence signal and background noise degrading the spatial resolution. We present high sensitive fluorescent TIRF-M using glass coverslips coated with one-dimensional photonic crystal (1DPC). The latter is made of dielectric multilayers optimized to generate a large field enhancement under TIR illumination at its free interface. Using a TIRF-microscope, we successfully demonstrate the capability of these substrates to enhance the fluorescence signal as compared to classical glass coverslips over fluorescently labeled HIV-1 and SARS-CoV-2 virus-like-particles imaging.
We introduce a nano-optical platform based on Bloch surface waves (BSWs) capable of exploiting the entire cleaved end facet of a multicore optical fiber. Interconnecting various fiber cores with BSWs directly at the end of a multicore fiber opens the perspective of highly compact complex optical functionalities for the design of “lab on fiber” devices. In counterpart, optical fibers provide a unique opportunity to obtain turnkey nano-optical functions addressing a vast application domain ranging from telecommunications to medical sensing. To show the full potential of our platform, we demonstrate a multiplexing function between three fiber cores.
We introduce a nano-optical platform based on Bloch surface waves (BSWs) capable of exploiting the entire cleaved end facet of a multicore optical fiber. Interconnecting various fiber cores with BSWs directly at the end of a multicore fiber opens the perspective of highly compact complex optical functionalities for the design of “lab on fiber” devices. In counterpart, optical fibers provide a unique opportunity to obtain turnkey nano-optical functions addressing a vast application domain ranging from telecommunications to medical sensing. To show the full potential of our platform, we demonstrate a multiplexing function between three fiber cores.
Total Internal Reflection Fluorescence (TIRF) Microscopy is widely used in cell biology to monitor dynamic biomolecular events occurring at the plasma membrane in living cells such as virus assemblies and particle budding. However, these studies are limited by the weak fluorescence signal and background noise degrading the spatial resolution. We present highly sensitive fluorescent TIRF imaging using classical glass coverslips coated with a resonant multi-dielectric thin film. Such dielectric multilayer is optimized to generate a large field enhancement under TIR illumination at the free interface. However, dielectric materials usually have low imaginary indices that are not experimentally measurable and introducing large discrepancies with the theory. We tackled the k issue by adjusting the oxygen level within the last thin layer to fully control its absorption. We then qualify such dielectric stack resonance in TIRFM configuration for fluorescent viruses imaging.
Optical resonances in continuous thin films have been under investigation for decades to push the limits of optical components or platforms for sensing or imaging applications. They occur under total internal reflection with the generation of surface plasmons in metallic films or of Bloch surface waves in dielectrics to generate large field enhancements in the near-field of the free interface. I will discuss both situations and give a quick comparison with advantages and drawbacks of both concepts in regard to common applications.
Design in a proper way, optical dielectric resonant multilayers can support huge optical field enhancement when working under total internal reflection. TIRFM - Total Internal Reflection Fluorescence Microscopy, also based on total internal reflection illumination, is used in cell biology imaging where many biological processes involve cell membranes and their immediate intracellular spatial environment (signaling, cellular traffic, adhesion...). We propose to develop an enhanced version of TIRFM by investigating the optimization, conception and implementation of dedicated optical dielectric resonant multilayers as the glass coverslip replacement. Model samples such as lipid bilayers with a known thickness will be first investigated but our ultimate goal is to image more complex biological processes such as viral budding, or molecular transport mechanisms such as exocytosis or endocytosis.
We present a comprehensive investigation of resonant all-dielectric multi-layers. We first introduce a numerical as well as analytical optimization based on admittance recurrence law. We then address the technological aspects of the fabrication using dual-ion-beam sputter deposition. Using the optimally fabricated structures, we carry out experiments to optically characterize their responses in the near and far fields. Previously, our optimization strategy had been based on maximizing the absorption within the dielectric stack [1] for any illumination conditions without altering the field enhancement. Recently, we have improved this process by introducing a single zero-admittance layer that allows defining the field enhancement localization within the multi-layer [2]. Similarly to the Kretschmann configuration for surface plasmon resonances (SPR), these resonant all-dielectric components work under total internal reflection but they can support field enhancements up to 104-105. From a theoretical point of view, the enhancement is not intrinsically limited (except for nonlinear phenomena or material damages under high flux), and it is therefore the illumination bandwidths (angular divergence and spectral range), which mainly limit the resulting field enhancement [3]. We will introduce the resonant all-dielectric components, demonstrate their potential for sensing applications and give a brief comparison with SPR [4].
The authors acknowledge the PSA group for financial support of this work, the ANRT for their support through the CIFRE program and the RCMO Group of the Institut Fresnel for the realization of the coatings. This work is part of the OpenLab PSA/AMU: Automotive Motion Lab through the StelLab network.
1- Appl. Phys. Lett. 103, 131102 (2013)
2- Phys. Rev. A 97, 023819 (2018)
3- Opt. Express 25, 14883 (2017)
4- Appl. Phys. Lett. 111, 011107 (2017)
KEYWORDS: Near field optics, Scattering, Near field, Near field scanning optical microscopy, Absorption, Prisms, Dielectric polarization, Refractive index, Light scattering, Resonance enhancement
Multi-dielectric thin films are usually studied as waveguiding structures with low absorption effect
because of the low imaginary part of the refractive index. However, when properly designed, we
demonstrated that multi-dielectric stacks can sustain large optical fields. We briefly present here
our design method leading the fabrication of such multi-dielectric stacks, which can be optimized
for arbitrary wavelengths, indices or polarizations. We then report on our experimental character-ization in near and far field, using a photon scanning tunneling microscope and scattering optical
setup, respectively. This investigation may find applications for ultra-sensitive optical sensors or
integrated light sources to mention a few.
Currently, the utilization of high power ultrafast lasers to induce optical changes in structures for the purpose of locally
drawing patterns with dimensions inferior to the diffraction limit is well-established and controlled. Using this technique,
we aim to modify the refractive index and/or the geometrical parameters of an optical interferential filter composed of
successive thin layers. This local optimization will then allow the improvement or tuning of the performances of the
optical filters. Thereafter, it is necessary to characterize these local modifications to achieve the final response of the
expected filter. In our work, we developed a dedicated optical system, based on Fabry-Perot interferometry, to measure
optical thickness, ranging from 10-3 to 10-4, with a high spatial resolution (in the order of 5×5μm). We present here our
preliminary results carried out on calibrated test samples.
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