Exploring the Residents' Perspective on Smart learning Modalities and Contents for Virtual Urology Education: Lesson Learned During the COVID-19 Pandemic. / Explorando la perspectiva de los residentes sobre las modalidades y contenidos de aprendizaje inteligente para la educación virtual de urología: lección aprendida durante la pandemia de la COVID-19.

PURPOSE: The COVID-19 outbreak has substantially altered residents' training activities. While several new virtual learning programs have been recently implemented, the perspective of urology trainees regarding their usefulness still needs to be investigated. METHODS: A cross-sectional, 30-item, web-based Survey was conducted through Twitter from April 4th, 2020 to April 18th, 2020, aiming to evaluate the urology residents' perspective on smart learning (SL) modalities (pre-recorded videos, webinars, podcasts, and social media [SoMe]), and contents (frontal lessons, clinical case discussions, updates on Guidelines and on clinical trials, surgical videos, Journal Clubs, and seminars on leadership and non-technical skills). RESULTS: Overall, 501 urology residents from 58 countries completed the survey. Of these, 78.4, 78.2, 56.9 and 51.9% of them considered pre-recorded videos, interactive webinars, podcasts and SoMe highly useful modalities of smart learning, respectively. The contents considered as highly useful by the greatest proportion of residents were updates on guidelines (84.8%) and surgical videos (81.0%). In addition, 58.9 and 56.5% of responders deemed seminars on leadership and on non-technical skills highly useful smart learning contents. The three preferred combinations of smart learning modality and content were: pre-recorded surgical videos, interactive webinars on clinical cases, and pre-recorded videos on guidelines. CONCLUSION: Our study provides the first global «big picture¼ of the smart learning modalities and contents that should be prioritized to optimize virtual Urology education. While this survey was conducted during the COVID-19 outbreak, our findings might have even more impact in the future.

Is remote live urologic surgery a reality? Evidences from a systematic review of the literature.

INTRODUCTION AND OBJECTIVES: The possibility of performing remote-surgery has been the goal to achieve, since the early development of the first surgical robotic platforms. This systematic review aims to analyse the state of the art in the field and to provide an overview of the possible growth of this technology. METHODS: All English language publications on Telementoring and Telesurgery for minimally invasive urologic procedures were evaluated. We followed the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) statement to evaluate PubMed®, Scopus®, and Web of Science™ databases (up to June 2019). RESULTS: Our electronic search identified a total of 124 papers in PubMed, Scopus, and Web of Science. Of these, 81 publications were identified for detailed review, which yielded 22 included in the present systematic review. Our results showed that remote surgery has been under-utilised until today, mostly due to the lack of appropriate telecommunication technologies. CONCLUSION: Remote live surgery is a growing technology that is catalyzing incremental interest. Despite not being yet reliable today on a regular basis in its most advanced applications, thanks to the advent of novel data-transmission technologies, telepresence might become a critical educational methodology, highly impacting the global healthcare system.

Time-resolved terahertz time-domain near-field microscopy.

We demonstrate a novel method for measuring terahertz (THz) photoconductivity of semiconductors on length scales smaller than the diffraction limit at THz frequencies. This method is based on a near-field microscope that measures the transmission of a THz pulse through the semiconductor following photoexcitation by an ultrafast laser pulse. Combining back-excitation of the sample using a Dove prism, and a dual lock-in detection scheme, our microscope design offers a flexible platform for near-field time-resolved THz time-domain spectroscopy, using fluences available to typical laser oscillators. Experimental results on a thin film of gallium arsenide grown by metal organic chemical vapor deposition are presented as a proof-of-concept, demonstrating the ability to map the complex conductivity as well as sub-ps dynamics of photoexcited carriers with a resolution of λ/10 at 0.5 THz.

Tailor-made directional emission in nanoimprinted plasmonic-based light-emitting devices.

We demonstrate an enhanced and tailor-made directional emission of light-emitting devices using nanoimprinted hexagonal arrays of aluminum nanoparticles. Fourier microscopy reveals that the luminescence of the device is not only determined by the material properties of the organic dye molecules but is also strongly influenced by the coherent scattering resulting from periodically arranged metal nanoparticles. Emitters can couple to lattice-induced hybrid plasmonic-photonic modes sustained by plasmonic arrays. Such modes enhance the spatial coherence of an emitting layer, allowing the efficient beaming of the emission along narrow angular and spectral ranges. We show that tailoring the separation of the nanoparticles in the array yields an accurate angular distribution of the emission. This combination of large-area metal nanostructures fabricated by nanoimprint lithography and light-emitting devices is beneficial for the design and optimization of solid-state lighting systems.

Photo-generated THz antennas.

Electromagnetic resonances in conducting structures give rise to the enhancement of local fields and extinction efficiencies. Conducting structures are conventionally fabricated with a fixed geometry that determines their resonant response. Here, we challenge this conventional approach by demonstrating the photo-generation of THz linear antennas on a flat semiconductor layer by the structured optical illumination through a spatial light modulator. Free charge carriers are photo-excited only on selected areas, which enables the realization of different conducting antennas on the same sample by simply changing the illumination pattern, thus without the need of physically structuring the sample. These results open a wide range of possibilities for the all-optical spatial control of resonances on surfaces and the concomitant control of THz extinction and local fields.

Surface lattice resonances strongly coupled to Rhodamine 6G excitons: tuning the plasmon-exciton-polariton mass and composition.

We demonstrate the strong coupling of surface lattice resonances (SLRs)--hybridized plasmonic/photonic modes in metallic nanoparticle arrays--to excitons in Rhodamine 6G molecules. We investigate experimentally angle-dependent extinction spectra of silver nanorod arrays with different lattice constants, with and without the Rhodamine 6G molecules. The properties of the coupled modes are elucidated with simple Hamiltonian models. At low momenta, plasmon-exciton-polaritons--the mixed SLR/exciton states--behave as free-quasiparticles with an effective mass, lifetime, and composition tunable via the periodicity of the array. The results are relevant for the design of plasmonic systems aimed at reaching the quantum degeneracy threshold, wherein a single quantum state becomes macroscopically populated.

Enhanced and directional emission of semiconductor nanowires tailored through leaky/guided modes.

Photoluminescence from finite semiconductor nanowires is theoretically investigated, exploring and predicting their antenna-like properties for light emission in a variety of configurations of interest in Nanophotonics. The theoretical analysis is based on the leaky/guided mode dispersion relation for infinite nanowires, which govern the local density of available electromagnetic states. Light emission from finite nanowires is then numerically investigated in various scenarios with regard to its enhancement and directionality. A simple analytical model is derived that, upon tuning leaky/guided mode coupling through dipole position/orientation and nanowire length, allows us to predict their antenna-like behavior and thus to tailor photoluminescence (including magnetic dipole transitions) at will, with regard to both enhancement/inhibition and associated radiation patterns.

Near-field resonance at far-field-induced transparency in diffractive arrays of plasmonic nanorods.

We numerically demonstrate that a periodic array of metallic nanorods sustains a maximum near-field enhancement and a far field (FF)-induced transparency at the same energy and in-plane momentum. The coupling of bright and dark plasmonic lattice resonances, and electromagnetic retardation along the nanorod length, are responsible for this effect. A standing wave with a quadrupolar field distribution is formed, giving rise to a collective suppression of FF scattering and simultaneously enhanced local fields.

Hybrid plasmonic-photonic modes in diffractive arrays of nanoparticles coupled to light-emitting optical waveguides.

We study the hybridized plasmonic-photonic modes supported by two-dimensional arrays of metallic nanoparticles coupled to light-emitting optical waveguides. Localized surface plasmon polaritons in the metallic nanoparticles can couple to guided modes in the underlying waveguide, forming quasi-guided hybrid modes, or to diffracted orders in the plane of the array, forming surface lattice resonances. We consider three kinds of samples: one sustains quasi-guided modes only, another sustains surface lattice resonances only, and a third sample sustains both modes. This third sample constitutes the first demonstration of simultaneous coupling of localized surface plasmons to guided modes and diffracted orders. The dispersive properties of the modes in the samples are investigated through light extinction and emission spectroscopy. We elucidate the conditions that lead to the coexistence of surface lattice resonances and quasi-guided hybrid modes, and assess their potential for enhancing the luminescence of emitters embedded in the coupled waveguide. We find the largest increase in emission intensity for the surface lattice resonances, reaching up to a factor of 20.

Light-emitting waveguide-plasmon polaritons.

We demonstrate the generation of light in an optical waveguide strongly coupled to a periodic array of metallic nanoantennas. This coupling gives rise to hybrid waveguide-plasmon polaritons (WPPs), which undergo a transmutation from plasmon to waveguide mode and vice versa as the eigenfrequency detuning of the bare states transits through zero. Near zero detuning, the structure is nearly transparent in the far-field but sustains strong local field enhancements inside the waveguide. Consequently, light-emitting WPPs are strongly enhanced at energies and in-plane momenta for which WPPs minimize light extinction. We elucidate the unusual properties of these polaritons through a classical model of coupled harmonic oscillators.

Nanoscale free-carrier profiling of individual semiconductor nanowires by infrared near-field nanoscopy.

We report quantitative, noninvasive and nanoscale-resolved mapping of the free-carrier distribution in InP nanowires with doping modulation along the axial and radial directions, by employing infrared near-field nanoscopy. Owing to the technique's capability of subsurface probing, we provide direct experimental evidence that dopants in interior nanowire shells effectively contribute to the local free-carrier concentration. The high sensitivity of s-SNOM also allows us to directly visualize nanoscale variations in the free-carrier concentration of wires as thin as 20 nm, which we attribute to local growth defects. Our results open interesting avenues for studying local conductivity in complex nanowire heterostructures, which could be further enhanced by near-field infrared nanotomography.

Lighting up multipolar surface plasmon polaritons by collective resonances in arrays of nanoantennas.

We demonstrate the coupling of multipolar surface plasmons with photonic modes in periodic arrays of metallic nanoantennas. This coupling leads to sharp resonances known as lattice surface modes. In spite of the weak interaction of multipolar surface plasmons with light, lattice surface modes provide an efficient radiative decay channel for emitters in the proximity of the array. We observe a tenfold emission enhancement of dyes coupled to lattice resonances. Lattice surface modes light up multipolar plasmonic resonances, opening new possibilities for fluorescence spectroscopies.

Long-range surface polaritons in ultra-thin films of silicon.

We present an experimental and theoretical study of the optical excitation of long-range surface polaritons supported by thin layers of amorphous silicon (a-Si). The large imaginary part of the dielectric constant of a-Si at visible and ultraviolet (UV) frequencies allows the excitation of surface polariton modes similar to long-range surface plasmon polaritons on metals. Propagation of these modes along considerable distances is possible because the electric field is largely excluded from the absorbing thin film. We show that by decreasing the thickness of the Si layer these excitations can be extended up to UV frequencies, opening the possibility to surface polariton UV optics compatible with standard Si technology.

Optical control over surface-plasmon-polariton-assisted THz transmission through a slit aperture.

We demonstrate optical control over the transmission of terahertz (THz) radiation through a single subwavelength slit in an otherwise opaque silicon wafer. The addition of periodic corrugation on each side of the wafer allows coupling to surface plasmon polaritons, so that light not impinging directly on the slit can contribute to the transmission. A significant enhancement of the THz transmission can be achieved through control of the surface wave propagation length by excitation at optical wavelengths. The observed transmission increase is in distinct contrast to the reduction reported for photoexcitation of arrays of holes in semiconductors.

Modification of the photoluminescence anisotropy of semiconductor nanowires by coupling to surface plasmon polaritons.

We demonstrate efficient modification of the polarized light emission from single semiconductor nanowires by coupling this emission to surface plasmon polaritons on a metal grating. The polarization anisotropy of the emitted photoluminescence from single nanowires is compared for wires deposited on silica, a flat gold film, and a shallow gold grating. By varying the orientation of the nanowire with respect to the grating grooves, the large intrinsic polarization anisotropy can be either suppressed or enhanced. This modification is interpreted by the appearance of an additional emission channel induced by surface plasmon polaritons and their conversion to p-polarized radiation at the grating.

All-optical switching of the transmission of electromagnetic radiation through subwavelength apertures.

Unprecedented optical control of the surface plasmon polariton assisted transmission of terahertz radiation through subwavelength apertures is rendered possible by carrier-induced changes to the dielectric properties of a semiconductor grating. Although the study presented is static, the extension of our approach to dynamic switching and tuning is deemed straightforward, opening the way for the realization of ultrafast surface plasmon based devices.

Thermal switching of the enhanced transmission of terahertz radiation through subwavelength apertures.

We demonstrate that the extraordinary transmission of terahertz radiation through semiconductor gratings of subwavelength apertures can be switched completely by varying the temperature. The enhanced transmission, which is due to the resonant tunneling of surface plasmon polaritons that can be excited in semiconductors at terahertz frequencies, is controlled by thermally modifying the density of free carriers. The transmission through metal gratings cannot be switched in the same way since the carrier density is temperature independent. Thus semiconductors offer an interesting alternative to metals in enhancing the transmission of electromagnetic radiation.

Propagation of surface plasmon polaritons on semiconductor gratings.

We present time-domain measurements of terahertz surface plasmon polaritons (SPPs) propagating on gratings structured on silicon surfaces. Using single-cycle pulses of terahertz radiation to excite SPPs in a broad frequency range, we observe that the efficient SPPs scattering on the semiconductor periodic structure introduces significant dispersion and modifies the SPPs propagation. A stop gap, or a frequency range where SPPs are Bragg reflected, is formed by the structure. This gap depends strongly on the Si doping density and type. The resonant scattering at the edge of the gap reduces the group velocity by more than a factor of 2. The measurements show a good agreement with our numerical calculations based on the reduced Rayleigh equation.