J.M. López-Higuera

University of Cantabria | UNICAN · Photonics Engineering Group. Department of Electronics Technology, Systems and Automation Engineering

An Adaptive Spiral Phase Plate (ASPP) based on liquid crystal (LC) and the transmission electrode technique is theoretically and experimentally demonstrated. This ASPP design enables the generation of high-quality optical vortices with topological charges ranging from ±1 to ±4 using a single device, with higher charges being directly achievable by...

This work involves exploring non-invasive sensor technologies for data collection and preprocessing, specifically focusing on novel thermal calibration methods and assessing low-cost infrared radiation sensors for facial temperature analysis. Additionally, it investigates innovative approaches to analyzing acoustic signals for quantifying coughing...

The visualization of 2D clinical data often relies on color-coded images, but different colormaps can introduce cognitive biases, impacting result interpretation. Moreover, when using color for diagnosis with multiple biomarkers, the application of distinct colormaps for each parameter can hinder comparisons. Our aim was to introduce a visualizatio...

In this study, a new wireless electronic circuitry to analyze weight distribution was designed and incorporated into a chair to gather data related to common human postures (sitting and standing up). These common actions have a significant impact on various motor capabilities, including gait parameters, fall risk, and information on sarcopenia. The...

All-dielectric metasurfaces supporting resonant quasi-bound states in the continuum (qBIC) offer an ideal platform for various applications relying on intense light-matter interaction in highly localized and enhanced fields. Here, we propose a dielectric metasurface composed of hollow GaP nanocuboid quadrumers periodically arranged on a silica subs...

The two main problems of dielectric metasurfaces for sensing and spectroscopy based on electromagnetic field enhancement are that resonances are mainly localized inside the resonator volume and that experimental Q-factors are very limited. To address these issues, a novel dielectric metasurface supporting delocalized modes based on quasi-bound stat...

We theoretically and experimentally investigate a metasurface supporting a silicon-slot quasi-bound state in the continuum (qBIC) mode resonating in the near-infrared spectrum. The metasurface is composed of circular slots etched in a silicon layer on a sapphire substrate. The symmetry of the metasurface unit cell is reduced in order to provide acc...

A wavelength-switchable L-band erbium-doped fiber laser (EDFL) assisted by an artificially controlled backscattering (ACB) fiber reflector is here presented. This random reflector was inscribed by femtosecond (fs) laser direct writing on the axial axis of a multimode fiber with 50 µm core and 125 µm cladding with a length of 17 mm. This microstruct...

This work presents the application of an experimental nematic liquid crystal (LC) mixture (1929) in a large aperture lens. The LC material is composed of terphenyl and biphenyl derivatives compounds with an isothiocyanate terminal group and fluorinated lateral substituents. The substitution with a strongly polar isothiocyanate group and an aromatic...

Quasi-dark resonances exhibiting antiferromagnetic order are theoretically investigated in a near-infrared metasurface composed of square slotted rings etched in a thin silicon layer on glass substrate. Access to the quasi-dark mode is achieved by reducing the symmetry of the metasurface according to the findings of a detailed group theory analysis...

Plasma optical spectroscopy and laser-induced breakdown spectroscopy (both on and off-line) are used in this work to analyze the effects of different perturbations applied to a tungsten inert gas welding process. This approach enables the analysis and comparison of the spectra acquired with the two setups, thus providing more information about the...

Thanks to their lower losses and sharper resonances compared to their metallic counterparts, all-dielectric metasurfaces are attracting a quickly growing research interest. The application of such metasurfaces in the field of refractive index sensing is extremely attractive, especially due to the expected high performance and the simplicity of the...

In this work, a silicon metasurface designed to support electromagnetically induced transparency (EIT) based on quasi-bound states in the continuum (qBIC) is proposed and theoretically demonstrated in the near-infrared spectrum. The metasurface consists of a periodic array of square slot rings etched in a silicon layer. The interruption of the slot...

This work presents a novel kind of microfluidic refractive index sensor based on a microbubble-phase-shifted fibre Bragg grating that is highly sensitive to the refractive index of the medium in the bubble.

An ultrafast laser fabricated lab-on-chip for analysis of microrganisms in fluids is presented. This prototype improves the photoexcitation of the microchannel fluid by a series of in-chip microlenses. Design, simulation and fabrication details are included.

A new and highly stable L-band fiber laser for sensing is demonstrated. An emission line at 1575.47 nm, was achieved using a special reflector. Good strain sensitivity, optical signal to noise ratio and output power stability were measured.

Resumen: En este trabajo se presenta un análisis experimental de las prestaciones alcanzadas por una cavidad láser en línea asistida por un reflector de fibra con retrodispersión controlada artificialmente (RFRCA). Dicho reflector ha sido concebido para permitir oscilación en un único modo longitudinal (SLM) en bandas C y L, presentando inestabilid...

Resumen: El uso de nuevas fibras de plástico perfluoradas (Cyclized Transparent Optical Polymer, CYTOP) para la inscripción de estructuras ópticas y la detección de diferentes parámetros ha empezado a cobrar importancia en la última década. Este trabajo presenta el diseño y fabricación de un sensor de índice de refracción externo optimizado para su...

Este trabajo presenta la evolución del espectro óptico de salida de una cavidad lineal de fibra óptica, en cuyo reflector se han realizado una serie de modificaciones en su índice de refracción de manera aleatoria mediante un láser de femtosegundos. Este reflector, formado por un tramo de fibra multimodo de 50 μm de diámetro de núcleo, y basado en...

In this work, an experimental analysis of the performance of different types of quasi-randomly distributed reflectors inscribed into a single-mode fiber as a sensing mirror is presented. These artificially-controlled backscattering fiber reflectors are used in short linear cavity fiber lasers. In particular, laser emission and sensor application fe...

In this invited review, we provide an overview of the recent advances in biomedical photonic sensors within the last five years. This review is focused on works using optical-fibre technology, employing diverse optical fibres, sensing techniques, and configurations applied in several medical fields. We identified technical innovations and advanceme...

Photodynamic therapy (PDT) is a cancer treatment with strong potential over well-established standard therapies in certain cases. Non-ionising radiation, localisation, possible repeated treatments, and stimulation of immunological response are some of the main beneficial features of PDT. Despite the great potential, its application remains challeng...

All-Dielectric Slot Metasurface with Ultra-High-Q resonances

A hybrid Raman-erbium random fiber laser with a half-open cavity assisted by chirped artificially controlled backscattering fiber reflectors is presented. A combination of a 2.4 km-long dispersion compensating fiber with two highly erbium-doped fiber pieces of 5 m length were used as gain media. A single random laser emission line centered at 1553....

In this work, a novel all-dielectric metasurface made of arrayed circular slots etched in a silicon layer is proposed and theoretically investigated. The structure is designed to support both Mie-type multipolar resonances and symmetry-protected bound states in the continuum (BIC). Specifically, the metasurface consists of interrupted circular slot...

An all‐dielectric metasurface exhibiting a strong toroidal resonance is theoretically designed and experimentally demonstrated as an angular‐dependent resonant polarization beam‐splitter in the microwave K‐band. The metasurface is fabricated by embedding a square periodic array of high‐permittivity ceramic cuboid resonators in a 3D‐printed substrat...

Depth cameras are developing widely. One of their main virtues is that, based on their data and by applying machine learning algorithms and techniques, it is possible to perform body tracking and make an accurate three-dimensional representation of body movement. Specifically, this paper will use the Kinect v2 device, which incorporates a random fo...

Is it possible to find deterministic relationships between optical measurements and pathophysiology in an unsupervised manner and based on data alone? Optical property quantification is a rapidly growing biomedical imaging technique for characterizing biological tissues that shows promise in a range of clinical applications, such as intraoperative...

In this work, we propose and experimentally demonstrate a new distributed short linear cavity fiber laser. At one of the cavity ends, fabricated by a commercial femtosecond fiber laser chirped pulse amplifier, an artificially controlled backscattering erbium doped fiber section has been connected. This distributed reflector acts also as a saturable...

A hybrid Raman-erbium random fiber laser (RFL) with a half-open cavity assisted by chirped artificially controlled backscattering fiber reflectors (ACBFRs) is presented. A combination of 2.4 km of dispersion compensating fiber (DCF) with two highly erbium-doped fiber (EDF) pieces of 5 m length was used as gain medium. A single random laser emission...

A method of measuring the refractive index of liquid based on the change of speckle contrast in fiber is presented. The correlation of propagation losses, proportional to the speckle contrast, is used when a section of U-shaped fiber without cladding is submerged in the liquid. The proposed method is easy to perform, simple and low cost, allows qui...

Development of a new adaptive algorithm for wavelength Bragg tracking in multimode fibers. It offers outstanding results for detection in ultrahigh temperatures (850 ºC), with a computation speed significantly higher than conventional algorithms.

Development of a high temperature sensor based on optical fiber laser generated from a cavity of reduced dimensions (43 mm) in Er-doped fiber. The mirror FBGs have been inscribed with femtosecond laser using the slit beam technique (Pl-b-Pl).

Development of enhanced Pl-b-Pl FBGs using slit beam technique with femtosecond laser, with improved control of the width and depth of the induced planes. Spectral response and homogeneity of induced change are far superior to PbP FBGs.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The consolidation of laser micro/nano processing technologies has led to a continuous increase in the complexity of optical fiber sensors. This new avenue offers novel possibilities for advanced sensing in a wide set of application sectors and, especially in the industrial and medical fields. In this review, the most important transducing structure...

The transmission electrode technique has been recently proposed as a versatile method to obtain various types of liquid-crystal (LC) lenses. In this work, an equivalent electric circuit and new analytical expressions based on this technique are developed. In addition, novel electrode shapes are proposed in order to generate different phase profiles...

Recently, lab-in-fiber (LIF) sensors have offered a new paradigm in many different scenarios, such as optofluidics, due to their ability to integrate different multiphysics sensor elements in a small space. In this Letter, the design and manufacture of a multiparameter sensing device is proposed, through the combination of an in-fiber air microcavi...

There is an increasing need to control light phase with tailored precision via simple means in both fundamental science and industry. One of the best candidates to achieve this goal are electro-optical materials. In this work, a novel technique to modulate the spatial phase profile of a propagating light beam by means of liquid crystals (LC), elect...

We demonstrate a technique to engineer cylindrical and Powell liquid crystal lenses with positive or negative optical power. The device is based on two indium-tin-oxide electrode combs and a microstructured voltage transmission electrode. The technique features the advantages of a multielectrode lens, albeit using a single lithographic step and onl...

In this work, a hybrid cladding waveguide (CWG) Mach-Zehnder interferometer (MZI) sensor inscribed by femtosecond laser is demonstrated. The CWG has been inscribed using adaptive optics and multiscan technique. It has been discovered that these waveguides exhibit a phase change dependent of the number of scans performed, allowing free spectral rang...

In this work, a novel technique to create positive-negative tunable liquid crystal lenses is proposed and experimentally demonstrated. This structure is based on two main elements, a transmission line acting as a voltage divider and concentric electrodes that distribute the voltage homogeneously across the active area. This proposal avoids all disa...

Enhanced OFS assisted by micro-drilled optical fibers acting as mirrors are demonstrated. Strain sensitivity improved more than one order of magnitude in comparison with FBG sensors using a 50 μm-waist micro-drilled taper as distributed reflector.

Imaging-based inspection techniques have practical advantages in the study and/or rehabilitation of artworks. They provide in some cases internal information on the status of the sample to be inspected. On the one hand, techniques based on active infrared thermography (IRT) are advantageous to obtaining complete images of the inspected parts, altho...

The relationship between wood and its degree of humidity is one of the most important aspects of its use in construction and restoration. The wood presents a behavior similar to a sponge, therefore, moisture is related to its expansion and contraction. The nondestructive evaluation (NDE) of the amount of moisture in wood materials allows to define,...

Many well-known algorithms for the color enhancement of hyperspectral measurements in biomedical imaging are based on statistical assumptions that vary greatly with respect to the proportions of different pixels that appear in a given image, and thus may thwart their application in a surgical environment. This article attempts to explain why this o...

In this paper, a novel approach for hybrid systems combining Raman distributed sensors with fiber Bragg grating (FBG) sensors to carry out distributed and quasi-distributed temperature/strain measurements was proposed and experimentally demonstrated. Three FBGs were inscribed by the point-by-point technique in a simple setup for type I femtosecond...

Sensors are the devices or systems developed to offer the capacity to capture, quantify and translate physical and chemical magnitudes to another domain, normally electrical. When the mentioned sensor system uses light based technologies in their key sensing part/s, then, they can be recognized as Light based Sensors [1] or Pho-tonic Sensors, PS. I...

Tilted diffraction gratings inscribed by femtosecond laser have been manufactured within multimode optical fibers, located 60 μm below the fiber end-face. These structures have been characterized by studying their phase change distribution along the grating and their cross section. Based on the previous characterization, the angles of diffraction o...

In this Letter, we present an analysis of the backscattering generated in a microdrilled tapered fiber within a short-linear-cavity fiber laser. We propose and experimentally demonstrate a fiber cavity laser based on a tapered optical fiber segment that generates artificially controlled backscattering. The 50-μm-waist taper was fabricated from a st...

Prototyping hyperspectral imaging devices in current biomedical optics research requires taking into consideration various issues regarding optics, imaging, and instrumentation. In summary, an ideal imaging system should only be limited by exposure time, but there will be technological limitations (e.g., actuator delay and backlash, network delays,...

An experimental study of a high temperature distributed optical fiber sensor based on Raman Optical-Time-Domain-Reflectometry (ROTDR) (up to 450 °C) and optical fibers with different coatings (polyimide/carbon, copper, aluminum and gold) is presented. Analysis of the distributed temperature sensor (DTS) measurements determined the most appropriate...

In this paper, we report on the ultrafast laser-induced birefringence, refractive index changes, and enhanced photoluminescence properties in the volume of neodymium (Nd), yttrium (Y) co-doped strontium fluoride ( SrF 2 ) and Nd, Y co-doped calcium fluoride ( CaF 2 ) crystals. The optical waveguides written with 500 kHz repetition rate provided low...

Early detection and diagnosis is a must in secondary prevention of melanoma and other cancerous lesions of the skin. In this work, we present an online, reservoir-based, non-parametric estimation and classification model that allows for this functionality on pigmented lesions, such that detection thresholding can be tuned to maximize accuracy and/o...

The spectral narrowing of Fiber Bragg Gratings (FBGs) introduced by unpumped Er-doped fiber (EDF) was analyzed for fiber lasers (FL). Owing to spatial hole burning (SHB), the spectral response of a virtual FBG can be employed for narrowing the band pass filter employed to determine the lasing wavelength of laser cavities. A common FL was mounted to...

This work presents an all-fiber wavelength converter based on a highly Er-doped fiber laser, which has been experimentally demonstrated. Frequencies from several kilohertz up to tens of gigahertz have been investigated. Making use of the gain competition in the amplifying medium, the wavelength conversion can be carried out over not only one lasing...

Fibre Bragg grating regeneration involves, at its simplest, the annealing and resurrection of a seed FBG through thermal annealing. Micro-Raman spectroscopy provides evidence that inscribing the seed structure has changed the thermal history of the glass so that whilst the annealing is identical in all areas, the local glass relaxation is different...