Low light night vision systems based on I2 tubes have been expanding rapidly over the past few years, due to a combination of the growing advancement of this technology and the increased pressure in the current climate. The design of a single optical bench able to fully characterize night vision devices is presented into this paper, focused more specifically on spot defects and goggle axes parallelism tests. These criteria are indeed very important: misalignment between the two binocular images may be one source of visual fatigue and could degrade task performance of the night vision user, and spot defects can act as visual distractions and may be large enough to mask critical information pilots need to conduct normal night vision operations. Thanks to HGH’s IRCOL bench, these two tests are integrated on the same support. Spot defect measurement utilizes machine vision algorithms to determine the size and location of the defects, and the parallelism measurement identifies the angular misalignment between the two channels under test. The spot defect test has also been completely automatized compared to the only visible test previously available All these results will be compiled and directly integrated into a computer-generated report that can be easily used for quality control or for maintenance applications.
In this work, we present a study on photonic biosensors based on Si3N4 asymmetric Mach-Zehnder Interferometers (aMZI) for Aflatoxin M1 (AFM1) detection. AFM1 is an hepatotoxic and a carcinogenic toxin present in milk. The biosensor is based on an array of four Si3N4 aMZI that are optimized for 850nm wavelength. We measure the bulk Sensitivity (S) and the Limit of Detection (LOD) of our devices. In the array, three devices are exposed and have very similar sensitivities. The fourth aMZI, which is covered by SiO2, is used as an internal reference for laser (a VCSEL) and temperature fluctuations. We measured a phase sensitivity of 14300±400 rad/RIU. To characterize the LOD of the sensors, we measure the uncertainty of the experimental readout system. From the measurements on three aMZI, we observe the same value of LOD, which is ≈ 4.5×10−7 RIU. After the sensor characterization on homogeneous sensing, we test the surface sensing performances by flowing specific Aflatoxin M1 and non-specific Ochratoxin in 50 mM MES pH 6.6 buffer on the top of the sensors functionalized with Antigen-Recognising Fragments (Fab’). The difference between specific and non-specific signals shows the specificity of our sensors. A moderate regeneration of the sensors is obtained by using glycine solution.
In this paper we demonstrate design, fabrication and characterization of polycrystalline silicon (poly-Si) photodetectors monolithically integrated on top of a silicon oxynitride (SiON) passive photonic circuit. The devices are developed for operation at the wavelength of ~850nm. Interdigitated PIN structures were designed and compared with conventional lateral PIN detectors. The devices, fabricated in standard CMOS technology, exhibit low dark current values of few nanoamperes. The best responsivity of 0.33A/W under a reverse bias of 9V was achieved for lateral PIN detectors with 3-μm interelectrode gap, coupled vertically to the optical waveguide. The applicability of devices for lab-on-chip biosensing has been proved by demonstrating the possibility to reproduce the sensor's spectral response.
In this article we describe the fabrication of free standing n-type porous silicon microcavity (MC) and their properties as liquid sensors. We have optimized the etching recipe to keep both large pore size and high quality factor (Q-factor). Thus the fabricated porous layers have pore size in the range of 40 to 110 nm and are thus compatible with mass transport across the porous layer. We found that MC with a Q-factor of 60 can measure down to 1.1*10-5 refractive index variations. Furthermore we analyze the role of non specific binding by comparing flow through versus flow over geometries. We compare these two approaches using different techniques and we show that flow over assay systematically overestimates the sensitivity of the device because of an inefficient rinse of the sample. Our work clearly indicates a limit in the reliability of measurements performed in flow over geometry unless specific controls are taken into account.
The main drawback of the rapidly evolving field of silicon photonics lies in the absence of efficient monolithically integrated radiation sources as a consequence of the indirect bandgap of Si and Ge. Relevant alternatives based on the hybrid combination of Si with optically active materials have to be technologically simple, temporally stable, and provide efficient coupling to the Si waveguides. Lead-sulfide nanocrystals (NCs) were blended into a polymer resist suitable for deep-UV- and electron-beam lithography and integrated into Si-based vertically slotted waveguides and ring resonators. The polymer both stabilizes the NC’s photoluminescence emission against degradation under ambient conditions and allows lithographic patterning of this compound material. After integration into the optoelectronic structures and upon optical pumping, intense photoluminescence emission from ring resonators was recorded at the output of bus-waveguides. The resonator quality factors were investigated for polymer-NC compounds with NC concentrations in the range between 0.1 and 8 vol%. The spontaneous emission rate enhancement for vertically slotted resonators was estimated to be a factor of two higher as compared to unslotted ones. The stable integration of colloidal NCs as well as the improved light coupling to silicon circuits is an important step in the development of silicon-based hybrid photonics.
In the last decade, Si based photonics has made major advances in terms of design, fabrication, and device implementation. But due to Silicon’s indirect bandgap, it still remains a challenge to create efficient Si-based light emitting devices. In order to overcome this problem, an approach is to develop hybrid systems integrating light-emitting materials into Si. A promising class of materials for this purpose is the class of semiconducting nanocrystal quantum dots (NCs) that are synthesized by colloidal chemistry. As their absorption and emission wavelength depends on the dot size, which can easily be controlled during synthesis, they are extremely attractive as building blocks for nanophotonic applications. For applications in telecom wavelength, Lead chalcogenide colloidal NCs are optimum materials due to their unique optical, electronic and nonlinear properties. In this work, we experimentally demonstrate the integration of PbS nanocrystals into Si-based photonic structures like slot waveguides and ring resonators as optically pumped emitters for room temperature applications. In order to create such hybrid structures, the NCs were dissolved into polymer resists and drop cast on top of the device. Upon optical pumping, intense photoluminescence emission from the resonating modes is recorded at the output of the waveguide with transmission quality factors up to 14000. The polymer host material was investigated with respect to its ability to stabilize the NC’s photoluminescence emission against degradation under ambient conditions. The waveguide–ring coupling efficiency was also investigated as function of the NCs concentrations blended into the polymer matrix. The integration of colloidal quantum dots into Silicon photonic structures as demonstrated in this work is a very versatile technique and thus opens a large range of applications utilizing the linear and nonlinear optical properties of PbS NCs at telecom wavelengths.
We report on the realization and characterization of a silicon-based integrated optical platform which implements a
vertical coupling scheme between a Whispering-gallery type microresonator and a buried dielectric waveguide. The
vertical coupling allows for the separation of the resonator and the waveguide into different planes, which enables one to
realize the optical components in different materials/thicknesses. The high optical quality of this cavity micro-optical
system follows from the accurate planarization of the waveguide topography, which is achieved by multiple depositions-and-
reflows of a borophosphosilicate glass over strip waveguides. Importantly, we demonstrate the feasibility of our
approach for wafer-scale mass fabrication of freestanding planar resonators suspended in air and coupled to integrated
bus waveguides. This opens the door for the realization of stable all-integrated resonator systems for optomechanical and
metrological applications and has the potential to substitute today's complicated fiber-taper coupling schemes.
We describe the development of optical waveguides and adiabatic tapers based on SiON-glasses for a lab-on-chip device
with fluorescence optical detection. Sensing is based on evanescent near-field excitation of biomolecules captured on the
surface of a thin waveguide. First, the composition of SiON waveguides was optimized to reduce losses for visible light.
Waveguides with refractive index of ~1.63 showed propagation losses of ~0.8-0.9 dB/cm at 633 nm. A low loss adiabatic
taper was developed to convert efficiently the light from a multi mode waveguide into a thin mono-modal one. Design of
the taper was done by calculating numerically the transmission efficiency using a finite-difference time-domain method
(FDTD). Simulation results show that losses lower than ~1 dB are obtained for taper lengths of 100 to 300 micron, which
indicates an efficient mode conversion. Based on this, tapers of different lengths were realized by grayscale lithography
and by reactive ion etching. Their optical testing shows best insertion losses of ~1 dB at 633 nm for multimode to
monomode waveguide transitions.
Silicon photonics is the emerging optical interconnect technology where integrated nanophotonic components allow reaching high device density and improved optical functionalities. One key component is the optical microresonator. A particular kind of microresonator is the racetrack resonator where straight waveguide sections are used to achieve a large value of the coupling coefficient with a bus waveguide for any light polarization state. It is our aim to study the performances of racetrack resonators fabricated on silicon on insulator via CMOS processing. We experimentally investigated different multiple resonator designs where box-shaped filter characteristic, Vernier effect, and coupled resonator induced transparency effects are obtained. We demonstrate that racetrack resonators are instrumental to several different functions in nanophotonics and that the actual lithographic process is fully capable of building these structures.
The use of broadband efficient sensitizers for Er3+ ions relaxes the expensive conditions needed for the pump source and
raises the performances of the optical amplifier. Within this context Si nanoclusters (Si-nc) in silica matrices have
revealed as optimum sensitizers and open the route towards electrically pumped optical amplifiers. Up to date two have
been the main limiting issues for achieving absolute optical gain, the first one is the low quantity of erbium efficiently
coupled to the Si-nc while the second is the carrier absorption mechanism (CA) within the Si-nc, which generates
additional losses instead of providing amplification.
In this work we will present a detailed study of the optical properties of a set of samples prepared by confocal reactive
magnetron co-sputtering of pure SiO2 and Er2O3 targets. The material has been optimised in terms of the increasing of
Er3+-related PL intensity and lifetime as well as the decreasing down to 3 dB/cm of the propagation losses in the rib-loaded
waveguides outside the absorption peak of erbium. Our signal enhancement results show that we have been able
to reduce the CA losses to less than 0.2 dB/cm at pump fluxes as high as 1020 ph/cm2 s. Around 25% of the optically
active erbium population has been inverted through indirect excitation (pumping with a 476nm laser line), leading to
internal gain coefficients of more than 1 dB/cm.
Hybrid organic-inorganic waveguides based on ZnO-(3-glycidoxypropil)trimethoxisilane (GPTS) have been
fabricated by sol-gel route. A transparent sol of ZnO was added to the GPTS host and the resulting sol was deposited
on silica substrates by spin coating technique.
Waveguides with different molar composition (100-x)GPTS-xZnO (x=10, 20, 30) were investigated by different
diagnostic techniques. Morphological measurements were carried out by means of an AFM apparatus, and a
roughness of few nanometers was determinate for all the waveguides.
Optical properties such as refractive index, thickness, number of propagating modes and attenuation coefficient were
measured at 632.8, 543.5, 1319 and 1542 nm by the prism coupling technique as a function of the ZnO content.
Photoluminescence measurements showed a large luminescence band in the region between 350 nm to 600 nm with
a main peak centred at about 380 nm, due to the presence of ZnO nanoparticles.
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