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In recent years, bitcoin has been at the center of a debate: is it a financial asset or not? If it is an asset, what kind of asset is it? Is it a tradable, speculative asset, or is it a long-term investment? The debate has largely unfolded around the real nature of Bitcoin and its correlation with other asset classes. Some scholars have discussed the correlation coefficient of bitcoin using the S& P 500 Index, the Volatility Index, and gold. However, the debate is now sufficiently mature to discuss the reasons determining its correlation with other assets. We study the correlations of Bitcoin and one benchmark, a stock market index–specifically, the Nasdaq 100 Index. Our focus is on the correlation between Bitcoin and the Nasdaq 100 as a proxy for the most representative technology stocks. We show that the correlation between the two has grown substantially since 2018, and has increased more since the beginning of the COVID-19 pandemic.

Kinesthetic Motor Imagery (MKI) has been demonstrated to be a robust paradigm for Brain-Computer Interfaces (BCI). In this paper we present the characterization of KMI paradigm of three tasks of wrist and forearm of the right arm using Hurst exponent and variogram, preceding for ICA to map signals into source space. The results show high persistency an average of 0.76 ± 0.07 for KMI Pronation/Supination (PS), 0.82 ± 0.05 for KMI Flexion-Extension). (FE), and 0.90 ± 0.02 for KMI Abduction-Adduction (AA We found a significant difference between the three KMI tasks, useful for multimodal command in BCI.

Made available in DSpace on 2018-12-11T16:55:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-09-03 Slow light propagation through photonic crystal (PhC) slab devices has great potential to reduce the size and power consumption of silicon photonic optical circuits. Most commonly, slow light routing through photonic crystals is achieved by using W1 waveguide bends operating near their cutoff frequencies. Unfortunately, this leads to optical pulse distortion due the high group velocity dispersion (GVD) associated with these designs. In this work however, we study the coupling between slow light waveguides optimized for near-zero GVD and 60° PhC bends. Using numerical methods and the temporal coupled mode theory we assess the performance of single bends coupled to input/output waveguides, and S-bends composed of two cascaded bends. In the latter, we observe that the bend-waveguide quality factor has great impact over transmission and dispersion. We propose a novel 60° PhC bend design for routing optical modes while maintained reduced dispersion. This is achieved over a -3dB bandwidth of around 50 nm in devices with slowdown factor up to 40. We show that this 60° PhC bend has good stability under changes in S-bend length and fabrication induced disorder. These results can lead to great improvements in the design of monolithically integrated modulators, switches, (de)multiplexers, and filters based on photonic crystals, as well as on the routing of long optical buffers and delay lines. Electronic Systems Engineering Department, University of Sao Paulo, Sao Paulo, SP Brazil 05508-010 (e-mail: emerdemelo@usp.br) Telecommunications Engineering Department, Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Sao Joao da Boa Vista, Sao Paulo Brazil (e-mail: daniel.orquiza@sjbv.unesp.br) Electronic Systems Engineering Department, University of Sao Paulo, Sao Paulo, SP Brazil (e-mail: malayo@lme.usp.br)

Slow light propagation throughout photonic crystal slab waveguides have great potential to reduce the size and power consumption of active silicon photonic devices. A great effort has been done to understand the slow light mechanisms and their relations with the waveguide geometrical parameters. In this way, it is expected to control the waveguide dispersion characteristics and exploit the effects produced when slowing down light propagation speed, but avoiding, at the same time, the high group velocity dispersion (GVD) level drawbacks such as pulse broadening and distortion. Here, we present a concise methodology to perform an efficient near-zero GVD slow light photonic crystal waveguide oriented-design. We use a slow light flatness parameter for enabling a systematic comparison of slow light waveguide structures regarding their average group velocity and group index slope within a limited bandwidth. The results show the feasibility of obtain near-zero GVD slow light photonic crystal waveguide structures with slowdown factors up to 40, normalized delay-bandwidth products over 0.2, and dispersion lengths at the millimeter scale.

In this work, we present a numerical design of a pedestal waveguide as a suitable alternative for coupling between few-mode fibers and integrated devices. The proposed waveguide has a cylindrical core deposited over a pedestal base. Numerical simulations are performed to show that modes propagating in pedestal waveguides possess an electric field profile similar to the LP modes in few-mode fibers. The power coupling between these two devices can reach values up to than 96% (-0.18 dB). Besides this, the pedestal waveguide has low insertion loss (IL) and the return loss is around 8 dB. This approach is a suitable alternative in the study of multimode integrated devices in order to work alongside few-mode fibers.

In this work, the non-linear refractive index (n 2 ) of silicon oxynitride (SiO x N y ) is determined, obtaining a value for this material of n 2 = 2.11×10-19 m2/W. The results demonstrate that this material has interesting properties for the development of non-linear optical devices. The paper presents in detail the waveguide fabrication process using the pedestal technique, which allows using different materials since it does not require etching to define the sidewalls of the waveguides. We show the results of the measurement of the n2 employing the non-linear optical phenomena of Self-Phase Modulation (SPM).

This paper presents the design and post-process of a CMOS-MEMS IR emitter device implemented in standard AMS 0.35μm CMOS process. The IR emitter is based on thermal heating of a chain of tungsten vias implemented on the Back-End-Of-Line. This heating element is protected from oxidation with a SiO 2 film and is thermally isolated from the substrate. The IR light emitted from the heating element is directed through a waveguide made of SiO 2 and air, used as core and cladding layers, respectively. The optical waveguide is connected to a photodiode used as detector, implemented in the Front-End-Of-Line. The post-process used to isolate the thermal emitter and create the waveguide was done through a maskless post-process that selectively etched the SiO 2 layers and used the aluminum film as a sacrificial material. The release of both emitter and optical waveguide was confirmed by visual inspection using optical and electronic microscopes.

In this work we present the details regarding the fabrication process of pedestal based optical waveguides, using different materials with large optical nonlinearities as core layer. With the pedestal fabrication process it is possible to use novel materials that are highly inert to chemical etchants or alloys composed of heavy metal elements, since this technique does not require etching of the core material itself. Lateral confinement of light is performed through the fabrication of pedestals by Reactive Ion Etching (RIE) on the lower cladding. The last step in the fabrication process is the deposition of the core layer and, for this reason, etching this layer is no longer necessary. The materials used as core layer are Aluminum Nitride and Titanium oxynitride films, due to the fact that these materials present a great potential for the fabrication of Nonlinear Optics integrated devices.

In this work we review and summarize the recent developments regarding pedestal waveguide fabrication technology and demonstrate the applicability of this type of structure for Nonlinear Optics (NLO) integrated devices. Pedestals show great potential as a platform for exploring new optical materials. The fabrication process of this type of waveguide does not require etching of the core material itself, making it possible to explore materials that are highly inert to chemical etchants or alloys composed of heavy metal elements, which would not be usually suitable for this purpose otherwise. Lower propagation losses can be achieved with pedestal waveguide when compared to rib waveguides fabricated with different materials. Since the pedestal process allows the exploitation of novel materials, optical amplifiers with higher gain have been demonstrated using this procedure. We show that pedestals could also greatly benefit the field of nonlinear optics, where novel materials with high nonlinearities could be explored as well.

We report experimental results on pedestal waveguides produced with Yb3+ /Er3+ codoped PbO-GeO 2 thin films deposited by RF Sputtering for photonic applications. Losses around 2.5 dB/cm and 1.5 dB/cm were obtained at 632 and 1068 nm, respectively, for waveguides in the 20–100 µm width range. Internal gain of 6.0 dB and 4.0 dB, at 1530 nm, under 980 nm excitation, were measured for waveguides width of 80 and 14 µm, respectively. The present results show the possibility of using Yb3+/Er3+ codoped PbO-GeO 2 pedestal waveguide for optical amplifiers.

GaN and AlN have attracted a great attention in the photonics researches. The large band gaps of these materials turn them suitable for nanophotonic devices that operate in light ranges from visible to deep ultraviolet. The photonic band gap maps obtained from plane wave calculations of common structures in wurtzite GaN and also in AlN were presented and analyzed. A complete photonic band gap with flat bands in the M - K direction was observed in the triangular lattice of air holes in dielectric medium.

The antiresonant reflecting optical waveguide (ARROW) with hollow core and liquid core are one of the most promising technologies in Lab-on-a-Chips and optofluidic research. Motivated by this, in this paper we present the design, simulation and fabrication processes of hollow core ARROW built in Corning glass substrates and utilizing Si 3 N 4 /SiO 2 PECVD antiresonant reflecting multilayer films on the channel wall. Details about the TMM/FDM methodology developed for the simple and fast design of ARROW waveguides built with multilayer dielectric thin films deposited over rounded microchannels in glass substrates are exhibited. The preliminary results confirm the light confinement in the hollow core region of the fabricated waveguide structure but further experiment are needed to fully characterize the devices.

We present the production and characterization of TeO2-WO3-Bi2O3 thin films to be used as core layer in the fabrication of optical sensors based on Mach-Zehnder Interferometer (MZI) that has applications as pressure sensors, temperature sensors, chemical and biological sensors. The waveguides were fabricated from pedestal type obtained using conventional optical lithography procedures, followed by plasma etching and Sputtering deposition. Propagation losses around 2.0 dB/cm and 2.5 dB/cm were obtained at 633 and 1050 nm, respectively. Measurements were also performed to characterize the guide modes. Single-mode propagation at 630 and 1050 nm was observed for waveguides width up to 10 μm; larger waveguides width provided multi-mode propagation.