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In order to obtain analytical gain expression in Brillouin optical Fiber Amplifiers (BFAs), coupled intensity equations describing the interaction of pump and stokes waves must be solved simultaneously. For long optical fibers, although fiber loss is responsible for the pump depletion and nonnegligible effect, for short optical fibers less than 2 km, its effect can be discarded. In this paper, we provide an accurate analytic expression for the BFA gain for fiber lengths less than 2 km by discarding the optical fiber loss and show results of experimental validation.

A simple approach is proposed for determining peak frequencies, stress heights, stress lengths, full-width at half-maximum (FWHM), broadening and symmetry properties, of a composite Brillouin Gain Spectrum (BGS) which is obtained for the pulse lengths longer than the embedded stress lengths. The composite BGS is thus reconstructed in terms of extracted components. It is validated that the method is successful in determining every level of stress peaks and heights embedded in composite BGS.

Room-temperature highly sensitive microbolometers are becoming very attractive in infrared (IR) sensing with the increase in demand for the internet of things (IOT), night vision, and medical imaging. Different techniques, such as building extremely small-scale devices (nanotubes, etc.) or using 2D materials, showed promising results in terms of high sensitivity with the cost of challenges in fabrication and low-noise readout circuit. Here, we propose a new and simple technique on the application of joule heating on a clamped&ndash, clamped beam without adding any complexity. It provides much better uniformity in temperature distribution in comparison to conventional joule heating, and this results in higher thermal stresses on fixed ends. This consequently brings around 60.5&times, improvement in the overall temperature sensitivity according to both theory and COMSOL (multiphysics solver). The sensitivity increased with the increase in the stiffness constant, and it was calculated as 134 N/m for a device with a 60.5&times, improvement. A considerable amount of decrease in the operation temperature (36&times, below 383 K and 47&times, below 428 K) was achieved via a new technique. That&rsquo, s why the proposed solution can be used either to build highly reliable long-term devices or to increase the thermal sensitivity.

Goktas, Hasan/0000-0002-2195-9531 WOS: 000454463000028 A silicon-based light source presents an unreached goal in the field of photonics due to silicon's indirect electronic band structure preventing direct carrier recombination and subsequent photon emission. Here, we utilize inelastically tunneling electrons to demonstrate an electrically driven light emitting silicon-based tunnel junction operating at room temperature. We show that such a junction is a source for plasmons driven by the electrical tunnel current. We find that the emission spectrum is not given by the quantum condition where the emission frequency would be proportional to the applied voltage, but the spectrum is determined by the spectral overlap between the energy-dependent tunnel current and the modal dispersion of the plasmon. By coupling an internal electric field enhancement with an external k-vector matching grating, we were able to demonstrate a 10-fold increase in the internal efficiency and a 40-fold increase in overall quantum efficiency. Such an electron tunneling-based mechanism could lead to a new class of solid-state light sources with unique features such as down-scalability and temporal responses that are significantly shorter than that of light-emitting diodes. Air Force Office of Scientific ResearchUnited States Department of DefenseAir Force Office of Scientific Research (AFOSR) [FA9550-17-1-0377] V.S. is supported by Air Force Office of Scientific Research under the Award FA9550-17-1-0377. We thank Josh Conway for helpful discussions and Ergun Simsek for numerical analysis support.

We present a comprehensive analysis of the technique of Longitudinal-Mode-Filling (LMF) to reduce Stimulated Brillouin Scattering (SBS) limitations in Ytterbium Doped Fibre Amplifiers (YDFA), for the generation of nanosecond, temporally shaped pulses. A basic Master-Oscillator-Power-Amplifier (MOPA) system, comprising an output YDFA with 10 mu m-core active fibre, is experienced for benchmarking purposes. Input pulse-shaping is operated thanks to direct current modulation in highly multimode laser-diode seeds, either based on the use of Distributed Feed-Back (DFB) or of a Fibre Bragg Grating (FBG). These seeds enable wavelength control. We verify the effectiveness of the combination of LMF, with appropriate mode spacing, in combination with natural chirp effects from the seed to control the SBS threshold in a broad range of output energies, from a few to some tens of mu J. These variations are discussed versus all the parameters of the laser system. In accordance with the proposal of a couple of basic principles and with the addition of gain saturation effects along the active fibre, we develop a full-vectorial numerical model. Fine fits between experimental results and theoretical expectations are demonstrated. The only limitation of the technique arises from broadband beating noise, which is analysed thanks to a simplified, but fully representative description to discuss the signal-to-noise ratio of the amplified pulses. This provides efficient tools for application to the design of robust and cost-effective MOPAs, aiming to the generation of finely shaped and energetic nanosecond pulses without the need for any additional electro-optics. (C) 2014 Optical Society of America

Brussels Photonics Team (B-PHOT);Brussels-Capital Region;Fonds Wetenschappelijk Onderzoek (FWO);The Society of Photo-Optical Instrumentation Engineers (SPIE);Ville de Bruxelles Nonlinear Optics and Its Applications VIII; and Quantum Optics III -- 14 April 2014 through 16 April 2014 -- -- 110770 We present a comprehensive experimental study of the technique of Longitudinal Mode Filling (LMF) applied to the reduction of Stimulated Brillouin Scattering (SBS), in Ytterbium Doped Fibre Amplifiers (YDFA) at the wavelength of 1064 nm. Pulse durations and Mode Field Diameters (MFD) lie in the ranges of 10 - 100 ns and 10 - 35 ?m, respectively. Input pulse-shaping is implemented by means of direct current modulation in multimode Laser-Diode seeds. This evidences a number of interests in the development of robust and low cost Master Oscillator Power Amplifiers (MOPA). Highly energetic, but properly shaped, nanosecond pulses may be produced this way without any need of additional electro-optical means for in-line phase and amplitude modulation. Seeds consist of Distributed Feed- Back (DFB) and Fibre Bragg Gratings (FBG) with different fibre lengths. We demonstrate the benefit of LMF with properly controlled mode spacing, in combination with chirp effects due to fast current transients in the semiconductors, in order to deal with SBS thresholds in the range of a few to some hundred ?J. The variations of the SBS threshold are discussed versus the number of longitudinal modes, the operating conditions of the selected seed and pulse-shaping conditions. © 2015 SPIE.

Highly accurate closed-form analytical formula, based on the undepleted pump approximation (UPA), is derived for pump, Stokes and the gain of a Brillouin fiber amplifier (BFA) operating in the moderately depleted pump regime. The material loss of the medium, which is a strong effect in optical fibers, is taken into account. To define validity ranges of the solution, the threshold power of BFA is accurately determined. The obtained results are numerically and experimentally validated. The presented analysis can be used to accurately predict the performance of moderate-gain BFAs.