Towards photonic biosensing using a three-port mach-zehnder interferometer in a silicon nitride platform

Integrated photonics enables sensitive and label-free optical biosensors for the detection of chemical and biological substances and is therefore promising for future lab-on-chip solutions. In this article we present our current development of silicon nitride based integrated photonic biosensing devices working at telecom wavelengths. Our approach of three-port based interferometric sensing circumvents the issues of conventional Mach-Zehnder interferometers, providing a constant sensitivity, and allowing to use a fixed wavelength sensing scheme. Preliminary experimental results show that the fabricated devices work as expected from simulations.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Optimizing the limit of detection of waveguide-based interferometric biosensor devices

Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration that can be reliably observed, mainly depends on the sensors response to small refractive index changes, and the noise in the read-out system. While enhancements in the sensors response have been extensively studied, noise optimization has received much less attention. Here we show that order-of-magnitude enhancements in the limit of detection can be achieved through systematic noise reduction, and demonstrate a limit of detection of ~10 RIU with a silicon nitride sensor operating at telecom wavelengths

Evidence-based education. Scientific dangers and political advantages

En este trabajo se plantea que uno de los peligros de las nuevas democracias, cuya complejidad ha aumentado sin precedentes en las sociedades modernas, es, según Innerarity (2020), su simplificación. Una característica de estas modernas y complejas democracias es lo que el mismo autor denomina dataismo y que consiste en vincular la cuantificación con la verdad, relacionándola con una falsa idea de objetividad y de certidumbre engañosa que impide un conocimiento cabal de la realidad, lo que permitiría una toma de decisiones más ajustada a la problemática real. Ante los constantes problemas y complejidades de las sociedades, este dataismo produce una demanda de datos para poder legitimar la toma de decisiones política, vinculándola a una idea falaz de ciencia. En este contexto es donde la educación y la investigación basadas en la evidencia han cobrado relevancia. El problema es que dicha perspectiva parte de unos presupuestos muy diferentes a los que epistemológicamente constituyen la educación como disciplina de conocimiento. Por lo cual, esta perspectiva evidencialista se ve obligada, por un lado, a asumir lo que Wrigley (2019) llama reduccionismos para poder desplegar sus teorías e investigaciones; por otro lado, a entender la educación como un asunto técnico, una visión educativa que ya tuvo su época de esplendor y que parecía superada justo por no ofrecer respuestas de calidad a las prácticas de aula. Nuestro planteamiento es que, lejos de una preocupación política honesta por mejorar la educación, la idea que subyace es la creación de relatos políticos que den legitimidad a sus políticas. Nada mejor en la época del dataismo que usar lenguajes basados en datos y evidencias para conectar con marcos mentales de objetividad, verdad o ciencia, que den legitimidad a estos relato

Automatic design of high-performance fiber-chip surface grating couplers based on Floquet-Bloch mode analysis

We propose a new strategy to automatically design highly efficient fiber-chip surface grating couplers. High performance designs are achieved with a substantially reduced computational cost by combining Floquet-Bloch mode analysis with a multi-objective optimization technique (genetic algorithms)

Mitigating reflections in integrated gas sensors

Optical gas sensing for environmental monitoring has become an active research topic in the last decade. Among the different optical sensing configurations, silicon photonic integrated sensors stand as a compact, CMOS-compatible alternative. However, even small on-chip reflections can create significant fringes when the optical path length is varied, e.g., when the wavelength is swept for TDLAS-like measurements. These fringes can be critical for NIR sensors, as absorption signals are much weaker in this region than in the MIR. Here, we propose a signal-processing method based on minimum phase techniques: by increasing the measurement bandwidth to around 2 nm we can completely remove the reflection artifacts through processing.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Low limit of detection silicon photonic sensor with extremely-low-cost laser source

Integrated photonic biosensors have demonstrated low bulk detection limits down to 1e−7 refractive index units. Nevertheless, most rely on expensive optical sources, such as DFB lasers. Here, we experimentally demonstrate that with adequate sensor design comparable detection limits are achievable with a low-cost Fabry-Perot laser.European Union’s Horizon 2020, Marie Skłodowska-Curie grant agreement No 713721; Ministerio de Econom ́ıa y Competitividad (FEDER), Proyecto TEC2016-80718-R; Programa Operativo FEDER Andalucía 2014-2020 (UMA18-FEDERJA-219); Severo Ochoa program from Spanish MINECO, Grant No. SEV-2017-0706, Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Recent GRBs observed with the 1.23m CAHA telescope and the status of its upgrade

We report on optical observations of Gamma-Ray Bursts (GRBs) followed up by our collaboration with the 1.23m telescope located at the Calar Alto observatory. The 1.23m telescope is an old facility, currently undergoing upgrades to enable fully autonomous response to GRB alerts. We discuss the current status of the control system upgrade of the 1.23m telescope. The upgrade is being done by the ARAE our group, based on members of IAA (Instituto de Astrofiisica de Andalucia). Currently the ARAE group is responsible to develop the BOOTES network of robotic telescopes based on the Remote Telescope System, 2nd Version (RTS2), which controls the available instruments and interacts with the EPICS database of Calar Alto. Currently the telescope can run fully autonomously or under observer supervision using RTS2. The fast reaction response mode for GRB reaction (typically with response times below 3 minutes from the GRB onset) still needs some development and testing. The telescope is usually operated in legacy interactive mode, with periods of supervised autonomous runs under RTS2. We show the preliminary results of several GRBs followed up with observer intervention during the testing phase of the 1.23m control software upgrade.Comment: 15 pages, 7 figures. Accepted for publication in the Special issue "Robotic Astronomy" of Advances in Astronomy. It includes two iterations with the referee

Mid-infrared Suspended Waveguide Platform and Building Blocks

In this work we present our recent progress in the development of a platform for the mid-infrared wavelength range, based on suspended silicon waveguide with subwavelength metamaterial cladding. The platform has some intrinsic advantages, which make it a very promising candidate for sensing applications in the fingerprint region. Specifically, it can cover the full transparency window of silicon (up to a wavelength of 8 μm), only requires one lithographic etch-step and can be designed for strong light-matter interaction. Design rules, practical aspects of the fabrication process and experimental results of a complete set of elemental building blocks operating at two very different wavelengths, 3.8 μm and 7.67 μm, will be discussed. Propagation losses as low as 0.82 dB/cm at λo=3.8 μm and 3.1 dB/cm at λo=7.67 μm are attained, for the interconnecting waveguides.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Suspended silicon integrated platform for the long-wavelength mid-infrared band

The atmospheric-transmission window and the fingerprint region of many substances overlaps with the long-wave infrared band. This has enabled the emergence of a new path for photonic integrated circuits, which could exploit the potential applications of this wavelength range, including chemical and bio sensing. In this work we review our latest advances in the suspended silicon platform with subwavelength grating lateral cladding at 7.7-µm wavelength. Suspended waveguides only require one lithographic etch step and can be specifically designed to maximize sensitivity when used as sensors. Waveguides with propagation loss of 3.1±0.3 dB/cm are demonstrated, as well as bends with less than 0.1 dB/bend. Suspended waveguides based on shifted Bragg grating lateral cladding are also reported, with propagation loss of 5.1±0.6 dB/cm. These results prepare the ground for the development of a platform capable of covering the entire mid-infrared band. Keywords: suspended silicon, mid-infrared, long-wave infrared, subwavelength grating, Bragg.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Subwavelength metamaterial engineering for silicon photonics

Waveguides structured at the subwavelength scale frustrate di raction and behave as optical metamaterials with controllable refractive index. These structures have found widespread applications in silicon photonics, ranging from sub-decibel e ciency bre-chip couplers to spectrometers and polarization rotators. Here, we briefly describe the design foundations for sub-wavelength waveguide devices, both in terms of analytic e ective medium approximations, as well as through rigorous Floch-Bloquet mode simulation. We then focus on two novel structures that exemplify the use of subwavelength waveguides: mid-infrared waveguides and ultra-broadband beamsplitters.Universidad de M alaga,Campus de Excelencia Internacional Andalucía Tech. Ministerio de Econom a y Competitividad, Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad (cofi nanciado FEDER), Proyecto TEC2013-46917-C2-1-R, Proyecto TEC2016-80718-