Voluntary Service or Compulsory Service? Una nueva perspectiva del debate sobre el Servicio Militar Obligatorio en Gran Bretaña entre 1902 y 1914

En el presente artículo, tratamos de aproximarnos al debate existente en el Ejército británico en el período 1902- 1914 desde una perspectiva alternativa, referente a la defensa de los intereses de clase por parte de las élites dirigentes británicas. Además, expondremos y analizaremos otros factores aducidos, hasta ahora, por la historiografía así como la evolución del Servicio Militar Voluntario hasta su substitución por el Obligatorio en enero de 1916.In this article, we’ll attempt to approach the debate that took place in the British Army during the period 1902- 1914 from an alternative perspective, concerning to the defence of class interests by the British ruling elites. Besides, we’ll present and analyse other factors cited by the Historiography until the present time, as well as the evolution of the Voluntary Military Service until its substitution for the Compulsory Service in January 1916

Far-field characterization of the thermal dynamics in lasing microspheres

This work reports the dynamical thermal behavior of lasing microspheres placed on a dielectric substrate while they are homogeneously heated-up by the top-pump laser used to excite the active medium. The lasing modes are collected in the far-field and their temporal spectral traces show characteristic lifetimes of about 2 ms. The latter values scale with the microsphere radius and are independent of the pump power in the studied range. Finite-Element Method simulations reproduce the experimental results, revealing that thermal dynamics is dominated by heat dissipated towards the substrate through the medium surrounding the contact point. The characteristic system scale regarding thermal transport is of few hundreds of nanometers, thus enabling an effective toy model for investigating heat conduction in non-continuum gaseous media and near-field radiative energy transfer

Blue-green to near-IR switching electroluminescence from Si-rich silicon oxide/nitride bilayer structures

Blue green to near-IR switching electroluminescence (EL) has been achieved in a metal-oxide-semiconductor light emitting device, where the dielectric has been replaced by a Si-rich silicon oxide/nitride bilayer structure. To form Si nanostructures, the layers were implanted with Si ions at high energy, resulting in a Si excess of 19%, and subsequently annealed at 1000 °C. Transmission electron microscopy and EL studies allowed ascribing the blue-green emission to the Si nitride related defects and the near-IR band with the emission of the Si-nanoclusters embedded into the SiO2 layer. Charge transport analysis is reported and allows for identifying the origin of this twowavelength switching effect

Erbium emission in MOS light emitting devices: from energy transfer to direct impact excitation

The electroluminescence (EL) at 1.54 µm of metal-oxide-semiconductor (MOS) devices with Er3+ ions embedded in the silicon-rich silicon oxide (SRSO) layer has been investigated under different polarization conditions and compared with that of erbium doped SiO2 layers. EL time-resolved measurements allowed us to distinguish between two different excitation mechanisms responsible for the Er3+ emission under an alternate pulsed voltage signal (APV). Energy transfer from silicon nanoclusters (Si-ncs) to Er3+ is clearly observed at low-field APV excitation. We demonstrate that sequential electron and hole injection at the edges of the pulses creates excited states in Si-ncs which upon recombination transfer their energy to Er3+ ions. On the contrary, direct impact excitation of Er3+ by hot injected carriers starts at the Fowler-Nordheim injection threshold (above 5 MV cm−1) and dominates for high-field APV excitation

Non-linear optical properties of Ge-rich SiGe waveguides in the near and mid infrared

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Mid-infrared integrated wideband duel-polarization Fourier-transform spectrometer

International audienceDue to the unique vibrational/rotational frequencies in the mid infrared (MIR) fingerprint region, which scans from 500 to 1500 cm-1, molecules can be assuredly identified and quantified. Thus integrated on-chip mid infrared spectroscopic systems, with low power consumption and high performance, would show great value for numerous applications, such as medical diagnosis, astronomy, chemical and biological sensing or security. Different solutions can be envisioned as on-chip integrated spectrometers, such as Fourier-Transform spectrometers, echelle gratings, or arrayed waveguide gratings. Integrated spatial heterodyne Fourier-Transform spectrometer (SHFTS) shows relaxed fabrication tolerances while applying a phase and amplitude correction algorithm. Meanwhile, it provides high optical throughput and high spectral resolution compared with AWG or echelle gratings. However, up to now in the literature, most of the development of Fourier-Transform based spectrometer is based on silicon-on-insulator operating in the near infrared typically at 1.55 µm wavelength. Thereby the development of integrated Fourier-Transform spectrometer operating in the MIR covering the wide fingerprint region is highly desirable. In this work, we experimentally demonstrate the first polarization insensitive Fourier-Transform spectrometer operating in the mid infrared beyond 5 µm wavelength. The fabricated FTS which is based on the graded-index Ge-rich SiGe platform, contains 19 Mach-Zehnder interferometers with a linearly increasing path difference. A spectral resolution better than 15 cm-1 has been demonstrated within an unprecedented spectral range of 800 cm-1 (5 to 8.5 µm wavelength)

On-chip integrated resonators for long-wave infrared photonics

International audienceOn-chip optical resonators are extensively applied to many fields such as light sources through lasing or enhancement of material nonlinear effects, chemical and biological sensing, and optical network monitoring. Silicon-based on-chip resonators have been reported previously in near infrared (NIR) and shortwave infrared (SWIR), however integrated resonant structures remain still challenging for long-wave infrared (LWIR). In this work, we experimentally demonstrate the first on-chip integrated resonators in LWIR up to 8.4 µm. Two types of resonators, Fabry-Perot cavities and racetrack ring resonators, have been both investigated. Maximum quality factors Q = 2200 and Q = 3200 have been respectively observed for Fabry-Perot cavity and racetrack ring resonator at a wavelength around 8 µm. These resonant structures lay the foundation for new generation of integrated photonics circuits that open the path towards miniaturized multi-functional LWIR systems

Integrated broadband mid-infrared polarization insensitive Fourier-Transform spectrometer

International audienceDue to the rotational and vibrational frequency, molecules show unique absorption spectrum in the mid-infrared fingerprint region from 500 to 1500 cm-1. Hence, the demonstration of integrated on-chip spectrometers with compact sizes, cost-effective and high performance is important. Here, we demonstrate the first polarization insensitive broadband operational mid infrared spatial heterodyne Fourier-Transform spectrometer (SHFTS) working beyond 5 µm wavelength. A resolution better than 15cm-1 for both TE/TM polarizations has been experimentally demonstrated in an unprecedented bandwidth of 800 cm-1 (from 5 µm to 8.5 µm wavelength) for our integrated on-chip SHFTS, using a graded-index Ge-rich SiGe photonics platform

On-chip fourier-transform spectrometer based on spatial heterodyning tuned by thermo- optic effect

International audienceMiniaturized optical spectrometers providing broadband operation and fine resolution have an immense potential for applications in remote sensing, non-invasive medical diagnostics and astronomy. Indeed, optical spectrometers working in the mid-infrared spectral range have garnered a great interest for their singular capability to monitor the main absorption fingerprints of a wide range of chemical and biological substances. Fourier-transform spectrometers (FTS) are a particularly interesting solution for the on-chip integration due to their superior robustness against fabrication imperfections. However, the performance of current on-chip FTS implementations is limited by tradeoffs in bandwidth and resolution. Here, we propose a new FTS approach that gathers the advantages of spatial heterodyning and optical path tuning by thermo-optic effect to overcome this tradeoff. The high resolution is provided by spatial multiplexing among different interferometers with increasing imbalance length, while the broadband operation is enabled by fine tuning of the optical path delay in each interferometer harnessing the thermo-optic effect. Capitalizing on this concept, we experimentally demonstrate a mid-infrared SiGe FTS, with a resolution better than 15 cm−1 and a bandwidth of 603 cm−1 near 7.7 μm wavelength with a 10 MZI array. This is a resolution comparable to state-of-the-art on-chip mid-infrared spectrometers with a 4-fold bandwidth increase with a footprint divided by a factor two