14 research outputs found
Characterization of surface-states in a hollow core photonic crystal fiber
FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL E NĂVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOSurface or edge states represent an important class of modes in various photonic crystal systems such as in dielectric topological insulators and in photonic crystal fibers. In the later, strong attenuation peaks in the transmission spectrum are attributed to coupling between surface and core-guided modes. Here, we explore a modified implementation of the spatial and spectral interference method to experimentally characterize surface modes in photonic crystal fibers. Using an external reference and a non-uniform Fourier transform windowing, the obtained spectrogram allows clear observation of anti-crossing behavior at wavelengths in which surface and core modes are strongly coupled. We also detect surface modes with different spatial symmetries, and give insight into mode families couple to the fundamental or high-order core modes, as well as the existence of uncoupled surface modes.26253255432564FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL E NĂVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL E NĂVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICO2013/20180-32015/04113-008/57857-2Sem informação574017/2008-
Brillouin scattering self-cancellation
FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOCAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIORThe interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it.The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it.718FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOCAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIORFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOCAPES - COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIOR08/57857-2, 2012/17610-3, 2012/17765-7, 2013/20180-3574017/2008-9Sem informaçã
Effects of Ga+ milling on InGaAsP Quantum Well Laser with mirrors etched by Focused Ion Beam
InGaAsP/InP quantum wells (QW) ridge waveguide lasers were fabricated for the
evaluation of Ga+ Focused Ion Beam (FIB) milling of mirrors. Electrical and
optical proprieties were investigated. A 7% increment in threshold current, a
17% reduction in external quantum efficiency and 15 nm blue shift in the
emission spectrum were observed after milling as compared to the as cleaved
facet result. Annealing in inert atmosphere partially revert these effects
resulting in 4% increment in threshold current, 11% reduction in external
efficiency and 13 nm blue shift with the as cleaved result. The current-voltage
behavior after milling and annealing shows a very small increase in leakage
current indicating that optical damage is the main effect of the milling
process.Comment: 12 pages, 4 figure
Application of Quality of Experience in Networked Services: Review, Trend & Perspectives
Full text embargoed until 17.10.2019 (publisher's embargo period, 12 months
Resonant amplification via Er-doped clad Si photonic molecules: towards compact low-loss/high-Q Si photonic devices
FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOSilicon photonics routers and band-pass filters employing ring resonators are usually constrained by a trade-off between quality factors and insertion loss, which is even more pronounced in compact designs. Device real estate is another factor to be considered for compactness and cost reduction. We propose an approach to simultaneously reduce insertion losses and increase the quality factor in such devices, while minimizing footprint. This approach consists in replacing the standard SiO2 top cladding of Si devices by erbium-doped Al2O3 films with a single post-processing step. Experimental results confirm the effectiveness of the method, where 1 dB output power increase is observed for a single ring device, in addition to an increase of 5% in the Q factor. In some cases of structures comprised of multiple coupled resonators, i.e., photonic molecules, the observed value of power increase is as high as 2.6 dB, with a Q factor increase of 25% and loss reduction of 3 dB.155144149FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICO08/57857-22014/04748-2574017/2008-99. Advanced Research Workshop on Future Trends in Microelectronics (FTM)10 a 16 de Junho de 2018Sardinia, ItĂĄli
Single-electron tunneling PbS/InP neuromorphic computing building blocks
We study single-electron tunneling (SET) characteristics in crystalline PbS/InP junctions, that exhibit single-electron Coulomb-blockade staircases along with memory and memory-fading behaviors. This gives rise to both short-term and long-term plasticities as well as a convenient non-linear response, making this structure attractive for neuromorphic computing applications. For further insights into this prospect, we predict typical behaviors relevant to the field, obtained by an extrapolation of experimental data in the SET framework. The estimated minimum energy required for a synaptic operation is in the order of 1 fJ, while the maximum frequency of operation can reach the MHz range
Fiber taper diameter characterization using forward Brillouin scattering
CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOWe propose a fast and non-destructive method to characterize the absolute diameter and uniformity of micrometer-scale fiber tapers using a pump and probe forward Brillouin scattering setup. The fundamental torsional-radial acoustic mode supported by the wire is excited using a pulsed pump laser and oscillates at a frequency that is inversely proportional to the taper waist diameter. This standing time-varying torsional-radial wave induces polarization modulation on a probe signal, whose spectrum structure reveals the sample diameter and its non-uniformity. By comparing our results with measurements using scanning-electron microscopy, a relative deviation of 1% or less was demonstrated, and diameter non-uniformity of less than 0.5% could be detected.435995998CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO574017/2008-908/57857-22013/20180-
Context monitoring for improved system performance and QoE
Whereas some application domains show a certain consensus on the role of system factors, human factors, and context factors, QoE management of multimedia systems and services is still faced with the challenge of identifying the key QoE influence factors. In this chapter, we focus on the potential of enhancing QoE management mechanisms by exploiting valuable context information. To get a good grip on the basics we first discuss a general framework for context monitoring and define context information, including technical, usage, social, economic, temporal, and physical factors. We then iterate the opportunities and challenges in involving context in QoE monitoring solutions, as context may be, e.g., hard to ascertain or very situational. The benefits of including context in QoE monitoring and management are demonstrated through use cases involving video flash crowds as well as online and cloud gaming. Finally, we discuss potential technical realizations of context-aware QoE monitoring and management derived based on the SDN paradigm. © The Author(s) 2018