Alicia Fresno-Hernández

Bio: Alicia Fresno-Hernández is an academic researcher. The author has contributed to research in topics: Surface plasmon resonance & Materials science. The author has an hindex of 1, co-authored 1 publications receiving 2 citations.

Design and Experimental Implementation of a Multi-Cloak Paraxial Optical System

Abstract: Electromagnetic cloaking has being continuously pursued using a large variety of approaches. In recent years, this effect has been observed using either complex devices based on the so-called Transformation Optics or simple systems based on conventional optics with proper characteristics. In the latter case, a simple arrangement of lenses working in the paraxial regime can provide broadband visible cloaking in a wide area. In this work, we analyzed and generalized this method by proposing a five-lens system producing at least three potential invisible regions with a large cloaked area (>90% of the visual field). In particular, we developed the mathematical formalism and show, both numerically and experimentally, the successful operation of the cloaking system with the naked eye.

Temperature sensor based on gold nanoparticles deposition in plastic optical fiber

Abstract: This article presents a novel approach for fabricating a temperature sensor by depositing nanoparticles on the surface of a plastic optical fiber (POF). The sensor utilizes the principle of surface plasmon resonance (SPR) and exploits the temperature-dependent changes in refractive index (RI) of the surrounding medium. The nanoparticles are deposited over the fiber surface using a micropipette, and the resulting sensor is characterized using a custom-built experimental setup. The sensor showed a linear response to temperature changes in the range of 10°C to 35°C, with a sensitivity of 0.457 nm/°C. The proposed sensor has several advantages over existing temperature sensors, such as low cost, ease of fabrication, and compatibility with a wide range of optical fibers. Overall, this work demonstrates the potential of using SPR-based sensors for temperature sensing applications, and paves the way for future research in this area.

Opto-mechanically generated resonant field enhancement

Abstract: Abstract A link between the resonant cumulative field enhancement experienced by a chain of plasmonic nanoparticles in a light field and the orientation of the chain with respect to the field is obtained. We calculate analytically the optical torque and the equilibrium configuration and we show how stable orientations are triggered by the geometric resonance conditions. Analytical predictions are checked using numerical calculations based on the coupled dipoles method (CDA) for the particular case of a chain of silver nanoparticles. The reported resonance driven optical torque allows for a tuning of the orientation of the chain depending on radiation’s wavelength.

Downtaper on Multimode Fibers towards Sustainable Power over Fiber Systems

Abstract: This paper presents a transition taper for coupling light between optical fibers with different geometries and refractive index profiles used in Power over Fiber (PoF) systems. Global energy efficiency and costs are critical parameters when delivering high power to remote areas. High-power lasers have maximum coupling for large core fibers, while widespread multimode optical (OM1) fibers used in optical communications are cheaper. We study the optical losses between large core fibers (200 µm) and OM1 fibers (62.5 µm) theoretically and experimentally. We demonstrate that improvements of 2 dB can be obtained by adding the new tapered structure to the system, compared to the direct splice between both fibers. There is good agreement between measured and calculated loss values using a new Gaussian loss model to describe splices between tapered and straight fibers. The fabrication of the transition taper is also described. We also measure the numerical aperture (NA) changes in the downtaper zone and demonstrate that the lower the NA of the input light, the higher the efficiency improvement.

Paraxial ray optics cloaking

Abstract: Despite much interest and progress in optical spatial cloaking, a three-dimensional (3D), transmitting, continuously multidirectional cloak in the visible regime has not yet been demonstrated. Here we experimentally demonstrate such a cloak using ray optics, albeit with some edge effects. Our device requires no new materials, uses isotropic off-the-shelf optics, scales easily to cloak arbitrarily large objects, and is as broadband as the choice of optical material, all of which have been challenges for current cloaking schemes. In addition, we provide a concise formalism that quantifies and produces perfect optical cloaks in the small-angle (`paraxial') limit.

Paraxial Full-Field Cloaking

Abstract: We complete the `paraxial' (small-angle) ray optics cloaking formalism presented previously [Choi and Howell, Opt. Express 22, 29465 (2014)], by extending it to the full-field of light. Omnidirectionality is then the only relaxed parameter of what may be considered an ideal, broadband, field cloak. We show that an isotropic plate of uniform thickness, with appropriately designed refractive index and dispersion, can match the phase over the whole visible spectrum. Our results support the fundamental limits on cloaking for broadband vs. omnidirectionality, and provide insights into when anisotropy may be required.