In the strong light-matter interaction regime, quantum vacuum field effects on coupled hybrid states are highly enhanced. One building block of such hybrid quantum system is a plasmonic nanocavity coupled with quantum emitters in the strong coupling (SC) limit and further. Here, we design and fabricate a low-mode volume plasmonic cavity and observe plasmon resonances in the visible range, based on the nanoparticle over mirror (NPoM) array structure. We show spectral tunability of this resonance with the nanostructure dimensions, and good agreement between optical characterization and numerical simulations by FDTD.
Fluoranthene and Pyrene (PAHs) airborne particles are well known for their mutagenic and carcinogenic properties. Manipulation of such nanoparticles below 100 nm makes it challenging due to their low polarizability and dielectric properties. Current optical nano-tweezer designs such as trench, slot and Hybrid Plasmonic Waveguides (HPWG) provides a strong gradient force for trapping, but they often have ≤ 50 nm gaps and have very low fabrication tolerances. In this work, we show the modeling of optical forces and sensitivity of different waveguide structures to sense large numbers of particles to monitor the Air Quality Index (AQI). To increase the trapping gaps and sensitivity in HPWG, we have designed them to use radiation modes of the dielectric waveguides. We call this phenomenon a “mode-lift”. Here we present the numerical and experimental results of industrially compatible integrated photonic sensors such as strip, slot, subwavelength grating (SWG) and HPWG used for measuring AQI.
This work aims to develop polymer-based optical micro-resonator sensors, operating in the visible range and sensitive for homogeneous in-situ detection of pollutants in aqueous medium. This paper demonstrates that using a porous silica cladding (ns = 1.2) enhances significantly the interaction of the evanescent field with the analytes by modifying the propagation properties of the guided optical mode. The results improve sensitivity without complicating the design and avoiding surface chemical functionalization classically used for such application. Detection experiments based on real part refractive index change in the visible range have been conducted using different glucose concentrations. A sensitivity at the state-of-the-art of 255 ± 12 nm/RIU has been achieved at 760 nm for micro-resonator polymer waveguides on porous silica. These promising results enable the use of our devices in sensors to detect both real and imaginary parts of the analyzed medium refractive index, as well as analysis of complex environments.
This study presents the development and optimization of AlN-based optical waveguides and photonic devices for 1.55 μm applications, utilizing a CMOS-compatible sputtered thin film technology. The fabrication employs a two-step photoresist technique to fabricate AlN core waveguides with low propagation losses and other optical devices, such as a 1×2 multimode interference (MMI) coupler, Mach-Zehnder interferometers and ring resonators. The results of this study highlight the potential for efficient and cost-effective fabrication of AlN-based integrated optical circuits and pave the way for further research and development in the field of integrated optics.
Optical ring micro-resonators (OMR) can be integrated onto chips to obtain sensitive, robust, low cost and portable sensor systems. They are used for in-situ real time detection of specific molecules by specialized or non- specialized persons. Target analytes, homogeneously spread in the cladding layer, induces a complex refractive index variation Δncl of the OMR waveguides upper cladding.
In this study, we propose an optimized analytical approach to OMR designs in terms of bulk sensitivity.
Those type of sensors are based on the evanescent field sensing. Interaction between the evanescent field and the analytes induces resonance wavelengths modifications. The main sensing strategy is based on resonant wavelength shift measurement. However, contrast variation, due to the absorption coefficient linked to analytes concentration, can also be measured. Colorimetric reactions, used to obtain a specific sensor, change significantly the light intensity in a specific peak of the transmission spectrum. This is due to the complex formation between a specific ligand and a heavy metal, such as hexavalent chromium and 1,5 diphenylcarbazide.
From the well-known ring resonator’s transmission expression, we can establish an analytical model of sensitivity’s dependence on geometric dimensions. Sensitivity in influenced by the round-trip attenuation coefficient a, the auto-coupling coefficient τ, the optical path and the ratio of guided power into the cladding Γcl. We validated our approach with FDTD simulation of OMR’s response for a 15 μm radius. This analytical approach makes it possible, from the waveguide propagation structure and propagation losses, to obtain both the optimal ring radius and the resonator gap in order to obtain maximum sensitivity.
Based on optical characterization of OMR, measured variations of 1% power drop at resonance should allow variation measurement on the extinction coefficient of ∆ni = 10−6.
Point-of-care tests (POCT) are important for detecting illnesses and monitoring patients without the need of a medical laboratory. To be useful, POCT must be sensitive, specific, integrated, and affordable. Since the early 2000s, integrated photonics have offered a possible solution for this problem. In particular, silicon micro-ring resonators represent a compact and sensitive choice known in the industry. This paper details the design, fabrication, and characterization of two methods for improving the performance of ring resonators by engineering their cross section. More precisely, improving devices made out of silicon nitride in an industrial environment to work in the infrared (around 1.31 µm).
The first approach is to selectively excite the first order mode of the ring resonator’s waveguide. The first order mode, with its greater exposure to the sensing liquid than the fundamental mode, results in a higher device sensitivity. The second method consists in coupling a dielectric mode with a surface plasmon polariton (SPP) forming a hybrid plasmonic waveguide. Hybrid plasmonic waveguides combine the low losses of the dielectric mode with the high sensitivity of the SPP, which increases the sensitivity in comparison to conventional dielectric ring resonators. Furthermore, hybrid plasmonic micro-ring resonators make possible a stable and easy differential functionalization.
Through the optical characterization of the devices, this study shows an experimental sensitivity of first order ring resonators of over 200 nm/RIU* and of hybrid plasmonic devices of 300 nm/RIU*. This demonstrates improvement with respect to the reference silicon nitride dielectric ring (120 nm/RIU*). Characterizations were performed using a PolyDiMethylSiloxane (PDMS) fluidic system to prove the compatibility of the substrate to POCT applications.
This paper shows two alternative approaches to integrated nano-photonic sensing for point of care testing. The proposed structures, demonstrate not only a higher sensitivity, but consider selectivity and manufacturing issues, which are fundamental for POCT development.
*RIU = Refractive Index Unit
Recently, we developed a new family of 3D photonic hollow resonators which theoretically allow tight confinement
of light in a fluid (gaz or liquid): the photon cages. These new resonators could be ideal for sensing applications
since they not only localize the electromagnetic energy in a small mode volume but also enforce maximal overlap
between this localized field and the environment (i.e. a potential volume of nano-particles). In this work, we will
present numerical and experimental studies of the interaction of a photon cage optical mode with nano-emitters. For
this, PbS quantum dot emitters in a PDMS host matrix have been introduced in photon cages designed to have
optimal confinement properties when containing a PDMS-based active medium. Photoluminescence measurements
have been performed and the presence of quantum dot emitters in the photon cages has been demonstrated.
We report on design, simulation and fabrication of ultimate and compact 3D close-geometries optical microcavities.
These are based on the extension of the so-called 2.5D nanophotonic approach where a quasi 3D control of the photons
has been soon demonstrated by our group. A tight control of photons, spectrally and spatially, in a small air region
inside a circular regular pattern of high index material-based nanopillars is demonstrated when adjusting the number of
pillars, their diameters and the diameter of the pillar-circle. Bottom-up approach based on InP nanowires grown by
molecular beam epitaxy and top-down approach based on high aspect ratio anisotropic etching have been developed for
fabricating these optical microcavities.
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