RESUMEN

The laser is one of the greatest inventions in history. Because of its ubiquitous applications and profound societal impact, the concept of the laser has been extended to other physical domains including phonon lasers and atom lasers. Quite often, a laser in one physical domain is pumped by energy in another. However, all lasers demonstrated so far have only lased in one physical domain. We have experimentally demonstrated simultaneous photon and phonon lasing in a two-mode silica fiber ring cavity via forward intermodal stimulated Brillouin scattering (SBS) mediated by long-lived flexural acoustic waves. This two-domain laser may find potential applications in optical/acoustic tweezers, optomechanical sensing, microwave generation, and quantum information processing. Furthermore, we believe that this demonstration will usher in other multidomain lasers and related applications.

Asunto(s)

RESUMEN

Recent years have witnessed the tremendous development of fusing fiber-optic imaging with supervised deep learning to enable high-quality imaging of hard-to-reach areas. Nevertheless, the supervised deep learning method imposes strict constraints on fiber-optic imaging systems, where the input objects and the fiber outputs have to be collected in pairs. To unleash the full potential of fiber-optic imaging, unsupervised image reconstruction is in demand. Unfortunately, neither optical fiber bundles nor multimode fibers can achieve a point-to-point transmission of the object with a high sampling density, as is a prerequisite for unsupervised image reconstruction. The recently proposed disordered fibers offer a new solution based on the transverse Anderson localization. Here, we demonstrate unsupervised full-color imaging with a cellular resolution through a meter-long disordered fiber in both transmission and reflection modes. The unsupervised image reconstruction consists of two stages. In the first stage, we perform a pixel-wise standardization on the fiber outputs using the statistics of the objects. In the second stage, we recover the fine details of the reconstructions through a generative adversarial network. Unsupervised image reconstruction does not need paired images, enabling a much more flexible calibration under various conditions. Our new solution achieves full-color high-fidelity cell imaging within a working distance of at least 4 mm by only collecting the fiber outputs after an initial calibration. High imaging robustness is also demonstrated when the disordered fiber is bent with a central angle of 60°. Moreover, the cross-domain generality on unseen objects is shown to be enhanced with a diversified object set.

RESUMEN

Imaging through scattering media is a useful and yet demanding task since it involves solving for an inverse mapping from speckle images to object images. It becomes even more challenging when the scattering medium undergoes dynamic changes. Various approaches have been proposed in recent years. However, none of them are able to preserve high image quality without either assuming a finite number of sources for dynamic changes, assuming a thin scattering medium, or requiring access to both ends of the medium. In this paper, we propose an adaptive inverse mapping (AIP) method, which requires no prior knowledge of the dynamic change and only needs output speckle images after initialization. We show that the inverse mapping can be corrected through unsupervised learning if the output speckle images are followed closely. We test the AIP method on two numerical simulations: a dynamic scattering system formulated as an evolving transmission matrix and a telescope with a changing random phase mask at a defocused plane. Then we experimentally apply the AIP method to a multimode-fiber-based imaging system with a changing fiber configuration. Increased robustness in imaging is observed in all three cases. AIP method's high imaging performance demonstrates great potential in imaging through dynamic scattering media.

RESUMEN

Fibre optic technology is rapidly evolving, driven mainly by telecommunication and sensing applications. Excellent reliability of the manufacturing processes and low cost have drawn ever increasing attention to fibre-based sensors, e.g. for studying mechanical response/limitations of aerospace composite structures. Here, a vector bending and orientation distinguishing curvature sensor, based on asymmetric coupled multi-core fibre, is proposed and experimentally demonstrated. By optimising the mode coupling effect of a seven core multi-core fibre, we have achieved a sensitivity of - 1.4 nm/° as a vector bending sensor and - 17.5 nm/m-1 as a curvature sensor. These are the highest sensitivities reported so far, to the best of our knowledge. In addition, our sensor offers several advantages such as repeatability of fabrication, wide operating range and small size and weight which benefit its sensing applications.

RESUMEN

[This corrects the article DOI: 10.1038/s41377-018-0047-4.].

RESUMEN

Leveraging recent advances in space-division multiplexing, we propose and demonstrate turbulence-resistant free-space optical communication using few-mode (FM) pre-amplified receivers. The rationale for this approach is that a distorted wavefront can be decomposed into a superposition of the fundamental Gaussian mode and high-order modes of a few-mode fiber. We present the noise statistics and the sensitivity of the FM pre-amplified receiver, followed by experimental and numerical comparisons between FM pre-amplified receivers and single-mode (SM) pre-amplified receivers with or without adaptive optics. FM pre-amplified receivers for FSO can achieve high sensitivity, simplicity and reliability.

RESUMEN

In this paper, we review recent progress in disordered optical fiber featuring transverse Anderson localization and its applications for imaging. Anderson localizing optical fiber has a transversely random but longitudinally uniform refractive index profile. The strong scattering from the transversely disordered refractive index profiles generates thousands of guiding modes that are spatially isolated and mainly demonstrate single-mode properties. By making use of these beam transmission channels, robust and high-fidelity imaging transport can be realized. The first disordered optical fiber of this type, the polymer Anderson localizing optical fiber, has been utilized to demonstrate better imaging performance than some of the commercial multicore fibers within a few centimeters transmission distance. To obtain longer transmission lengths and better imaging qualities, glass-air disordered optical fibers are desirable due to their lower loss and larger refractive index contrast. Recently developed high air-filling fraction glass-air disordered fiber can provide bending-independent and high-quality image transport through a meter-long transmission distance. By integrating a deep-learning algorithm with glass-air disordered fiber, a fully flexible, artifact-free, and lensless fiber imaging system is demonstrated, with potential benefits for biomedical and clinical applications. Future research will focus on optimizing structural parameters of disordered optical fiber as well as developing more efficient deep-learning algorithms to further improve the imaging performance.

RESUMEN

Optical vortex beams that carry orbital angular momentum (OAM), also known as OAM modes, have attracted considerable interest in recent years as they can comprise an additional degree of freedom for a variety of advanced classical and quantum optical applications. While canonical methods of OAM mode generation are effective, a method that can simultaneously generate and multiplex OAM modes with low loss and over broad spectral range is still in great demand. Here, via novel design of an optical fiber device referred to as a photonic lantern, where the radial mode index ("m") is neglected, for the first time we demonstrate the simultaneous generation and multiplexing of OAM modes with low loss and over the broadest spectral range to date (550 nm). We further confirm the potential of this approach to preserve the quality of studied OAM modes by fusion splicing the end-facet of the fabricated device to a delivery ring-core fiber (RCF).

RESUMEN

We present a randomly disordered silica-air optical fiber featuring a 28.5% air filling fraction in the structured region, and low attenuation below 1 dB per meter at visible wavelengths. The quality of images transported through this fiber is shown to be comparable to, or even better than, that of images sent through commercial multicore imaging fiber. We demonstrate robust high-quality optical image transfer through 90 cm-long fibers with disordered silica-air structure, more than an order of magnitude improvement compared to previous disordered fiber imaging distances. The effects of variations of wavelength and feature size on transported image quality are investigated experimentally.

RESUMEN

Multimode optical fibers have seen increasing applications in communication, imaging, high-power lasers, and amplifiers. However, inherent imperfections and environmental perturbations cause random polarization and mode mixing, causing the output polarization states to be different from the input polarization states. This difference poses a serious issue for employing polarization-sensitive techniques to control light-matter interactions or nonlinear optical processes at the distal end of a fiber probe. Here, we demonstrate complete control of polarization states for all output channels by only manipulating the spatial wavefront of a laser beam into the fiber. Arbitrary polarization states for individual output channels are generated by wavefront shaping without constraining the input polarization. The strong coupling between the spatial and polarization degrees of freedom in a multimode fiber enables full polarization control with the spatial degrees of freedom alone; thus, wavefront shaping can transform a multimode fiber into a highly efficient reconfigurable matrix of waveplates for imaging and communication applications.

RESUMEN

The fibre-optic microwave photonic link has become one of the basic building blocks for microwave photonics. Increasing the optical power at the receiver is the best way to improve all link performance metrics including gain, noise figure and dynamic range. Even though lasers can produce and photodetectors can receive optical powers on the order of a Watt or more, the power-handling capability of optical fibres is orders-of-magnitude lower. In this paper, we propose and demonstrate the use of few-mode fibres to bridge this power-handling gap, exploiting their unique features of small acousto-optic effective area, large effective areas of optical modes, as well as orthogonality and walk-off among spatial modes. Using specially designed few-mode fibres, we demonstrate order-of-magnitude improvements in link performances for single-channel and multiplexed transmission. This work represents the first step in few-mode microwave photonics. The spatial degrees of freedom can also offer other functionalities such as large, tunable delays based on modal dispersion and wavelength-independent lossless signal combining, which are indispensable in microwave photonics.

Asunto(s)

Asunto(s)

RESUMEN

We demonstrate the first few-mode-fiber based passive optical network, effectively utilizing mode multiplexing to eliminate combining loss for upstream traffic. Error-free performance has been achieved for 20-km low-crosstalk 3-mode transmission in a commercial GPON system carrying live Ethernet traffic. The alternative approach of low modal group delay is also analyzed with simulation results over 10 modes.

Asunto(s)

RESUMEN

Este artículo desarrolla un punto de vista materialista en el terreno de los debates epistemológicos introducidos en la psicología y en la psicología social por el Construccionismo Social (no es posible pensar hoy sobre la epistemología en este campo sin pasar por sus aportaciones). Para ello se expone, en primer lugar, las interrogaciones críticas más relevantes introducidas por esta perspectiva. Después se dialogará con ellas al mostrar una propuesta a partir de algunos puntos de tensión con el Construccionismo Social. Finalmente, a modo de conclusión, se destacan las implicaciones éticas y políticas sobre los dos elementos planteados -sujeto-agente y objetividad situada-.

In this paper we develop a material point of view in terms of epistemological debates introduced in psychology and in social psychology by social constructionism (it's impossible today think about epistemology without going through their contributions). First, we show the most relevant critical questions done by this prospect. After we show our proposal on some points of tension with the social constructionism. Finally we emphasize the ethical and political implications of our materialistic point of view.

RESUMEN

Son muchos los sanitarios que sufren problemas podológicos por el uso de un calzado laboralinadecuado. El presente artículo pretende desglosar las virtudes y carencias del calzado de los sanitarios porexcelencia, el zueco. Y plantear cuales serían las características generales y específicas que deberían tener elcalzado adecuado para este grupo de profesionales, teniendo en cuenta sus actividades cotidianas (AU)

There are many health workers who suffer podiatrists problems as a consequence of an inappropriatefootwear. This article is going to show the strengths and the shortcomings of the main sanitary shoe, theclog. Moreover, it is going to show what are the general and the specific characteristics that a suitablefootwear should have for this group of professionals, taking into account the features of their dailyactivities (AU)

Asunto(s)

RESUMEN

Debido a su frecuencia en la vida diaria, son múltiples los esguinces de tobillos que tendremos que tratar a lo largo de nuestra carrera profesional. La figura de la enfermera y su rol, desarrollan un papel fundamental a lahora de la valoración, tratamiento y evolución del esguince de tobillo. Por todo, este trabajo tiene como propósito describir las principales característicasdel esguince de tobillo (aspectos anatómicos, mecanismos de producción, tipos de lesión, cuadro clínico), su exploración, diagnóstico y tratamiento; y finalmente proponer cuál es el papel enfermero en este problemade salud, tanto desde el punto de vista de los problemas de colaboración como de los diagnósticos enfermeros que pueden darse más frecuentemente en las personas que sufren un esguince de tobillo

Due to their frequency in daily life, it will be many sprained ankles that we will have to treat in our professional career. The nurse’s figure androle are of utmost importance in the assessment, treatment and progression of a sprained ankle.The aim of this article is therefore to describe the main characteristics of a sprained ankle (anatomical aspects, production mechanisms, types of lesions, clinical picture), its examination, diagnosis and treatment, and finally to suggest what the nursing role is in this health problem, from the point of view of collaboration problems and the nursing diagnosesthat may more frequently occur in people who have sustained a sprained ankle

Asunto(s)

Asunto(s)