A. García-Juárez

Experimental transmission in a fiber-radio system using a microwave photonic filter at 2.8GHz

This paper deals with the experimental transmission of analog TV-signal in a fiber-radio scheme using a microwave photonic filter. For that purpose, filtering of a microwave band-pass window located at 2.8 GHz is obtained by the interaction of an externally modulated multimode laser diode emitting at 1.5μm associated to the chromatic dispersion parameter of an optical fiber. Transmission of TVsignal coded on the microwave band-pass window is achieved over an optical link of 20.70 Km. Demodulated signal is transmitted via radiofrequency using printed antennas. This communication scheme has a potential application in the field of FTTx network architectures.

Modeling and performance analysis of an all-optical photonic microwave filter in the frequency range of 0.01-15 GHz

The generation, distribution and processing of microwave signals in the optical domain is a topic of research due to many advantages such as low loss, light weight, broadband width, and immunity to electromagnetic interference. In this sense, a novel all-optical microwave photonic filter scheme is proposed and experimentally demonstrated in the frequency range of 0.01-15.0 GHz. A microwave signal generated by optical mixing drives the microwave photonic filter. Basically, photonic filter is composed by a multimode laser diode, an integrated Mach- Zehnder intensity modulator, and 28.3-Km of single-mode standard fiber. Frequency response of the microwave photonic filter depends of the emission spectral characteristics of the multimode laser diode, the physical length of the single-mode standard fiber, and the chromatic dispersion factor associated to this type of fiber. Frequency response of the photonic filter is composed of a low-pass band centered at zero frequency, and several band-pass lobes located periodically on the microwave frequency range. Experimental results are compared by means of numerical simulations in Matlab exhibiting a small deviation in the frequency range of 0.01-5.0 GHz. However, this deviation is more evident when higher frequencies are reached. In this paper, we evaluate the causes of this deviation in the range of 5.0-15.0 GHz analyzing the parameters involved in the frequency response. This analysis permits to improve the performance of the photonic microwave filter to higher frequencies.

Method to transmit analog information by using a long distance photonic link with distributed feedback lasers biased in the low laser threshold current region

We describe an analog microwave photonic link system, which is used to transmit in a multiplexed way a TV signal over 30 km of standard optical fiber. The experimental setup is composed mainly by two distributed feedback (DFB) laser diodes emitting at 1500 nm. When these DFB lasers are operated in the low laser threshold current region, relaxation oscillation frequencies are obtained. Relaxation oscillations in the laser intensity can be seen as sidebands on both sides of the main laser line. The optical emissions generated in each laser are combined and amplified by using an erbium-doped fiber amplifier. Next, the amplified optical signal is detected by a fast photo-detector using direct detection method, and as result of this photo-detection, microwave signals are generated. Since microwave signals obtained by using this technique are tuned continuously; we can use them as electrical carriers to transmit simultaneously a TV signal at 4 and 5 GHz and over 30 km of standard optical fiber by using a Mach-Zehnder modulator. At the end of the optical link the modulated light is photo-detected in order to recover efficiently and successfully the analog TV signal.

Annealing effect on structural, morphological, and optical behaviors of CBD-CdS nanostructured films for solar cells

In the current work, the effect of an annealing process on structural, morphological, and optical behaviors of cadmium sulfide thin films is presented. A chemical bath deposition method for cadmium sulfide deposition is based on the use of glycine as a complexing agent. Cadmium sulfide thin films were grown by chemical bath deposition and annealed in a nitrogen atmosphere at 0, 100, 150, 200, and 250 °C for 30 minutes. Crystallographic and morphological studies of CdS thin films were performed by scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray diffraction. The optical behavior of CdS thin films was evaluated by UV-Visible spectroscopy and band gap values were calculated by approximation using a Tauc plot. After annealing, densified CdS films formed by nanostructured crystallites exhibit suitable band gap values and present relatively high transmittance in the visible region, allowing their application as a window material for solar cells.

Analog photonic link by using DFB lasers operated in the low laser threshold current region and external modulation

In this paper we describe an analog microwave photonic link system used to transmit simultaneously two TV signals. The experimental setup is composed mainly by two distributed feedback (DFB) laser diodes emitting at 1500 nm. When DFB lasers are operated in the low laser threshold current region, relaxation oscillation frequencies are obtained. Relaxation oscillations in the laser intensity can be seen as sidebands on both sides of the main laser line. The optical emissions generated in each laser are combined and amplified by using an Erbium-Doped Fiber Amplifier (EDFA). Next, the amplified optical signal is detected by a fast photo-detector using direct detection method and as result of this photo-detection microwave signals are generated. Microwave signals obtained by this technique are used as electrical carriers to transmit analog TV signals over 30 km of standard optical fiber by using a Mach-Zehnder modulator (MZM). At the end of the optical link the modulated light is photo-detected in order to recover efficiently and successfully the analog TV signals.

Microstructural and Optical Characterization of Single and Multilayers of ZnO for TFTs Active Layer

Polymeric particles loaded with biocompatible magnetic nanoparticles are promising platforms to perform therapy and diagnostic of diseases, acting as the so called theranostic agents. In this work, magnetite nanoparticles were synthesized by coprecipitation method and encapsulated with Polycaprolactone (PCL) and Poloxamer 188 polymers through the innovative Nano Spray Drying technique. X-Ray Diffraction and Infrared Spectroscopy confirmed that the formed particles are composed by PCL, Poloxamer and magnetite, with amount of magnetite determined as 3% by Thermogravimetric Analysis. Particles present a superparamagnetic-like behaviour at 300 K, having negligible coercivity. Dynamic Light Scattering and Scanning Electron Microscopy indicated that the hydrodynamic diameters are of 49 nm for magnetite nanoparticles and of approximately 600 nm for encapsulated particles, with aspect analogous to a “nanocookie” of a PCL/Poloxamer blend with magnetite nanoparticles embedded in it. Cytotoxicity assays presented IC 50 superior to 2.5 mg/mL for healthy cells and a higher viability of cancer cells in comparison to control, suggesting that the particles may have affinity for tumours, which can be useful for the intended biological applications.

Repulsive Function in Potential Field Based Control with Algorithm for Safer Avoidance

In this article, a collision avoidance scheme based on potential functions is proposed. The first part of the paper is intended to establish the equations of the dynamic model of the vehicle, potential attractive functions and nested saturation controller. In the second part, the repulsive scheme is developed. Along with the repulsive scheme, the controller constants are optimized, in order to perform a safer avoidance maneuver. The advantages of the proposed repulsive schemes compared with a conventional repulsive function are demonstrated by simulations.

Microstructural and optical characterizations of highly stable nanospheres of crystalline CdS via selective approach

A novel and selective approach to obtain highly stable and capping nanospheres of crystalline cadmium sulfide (CdS) via solution growth in cadmium nitrate tetrahydrate-thiourea-ligand-pH buffer systems using a Taguchi experimental design is presented. CdS characterization is carried out by laser diffraction particle size analyzer, X-ray diffraction, scanning electron microscope/energy dispersive X-ray spectroscopy, and UV-Vis absorption spectroscopy. Synthesized nanospheres of crystalline CdS with an average crystal particle diameter of 37.5 nm and a capping layer thickness of 17.7–35.7 nm (73 to 115 nm as capped nanoparticles) keep size and form stable in aqueous solution. These crystalline CdS nanospheres exhibit a 2.46 eV band gap, as well as, an optical bandwidth comprises in the visible range with potential applications in solar cells.

Microwave hybrid fiber-radio system based on optical heterodyne technique

We show a hybrid fiber-radio system incorporating optical microwave generation, wireless transmission, and optical long haul transmission. Microwave signal generation is achieved by using optical heterodyne technique in the frequency range of 0.1–4.0 GHz. The microwave signal obtained is used as demodulated signal as well as electrical carrier. Microwave signal is mixed with a TV-signal, and used to drive a Mach-Zehnder intensity modulator operating at 1.3 μm. At the end of the optical link of 28-km of single-mode fiber, the use of an antenna allows to detect the demodulated signal and recover the TV-signal.

Modulation of relaxation oscillation frequency of a DFB laser by using direct detection

Relaxation oscillation frequency is produced when a laser is operated in the low laser threshold current region. In this operation region, a semiconductor laser shows a smooth curve, where we can observe uncertainty into defining the onset of laser oscillation. Relaxation oscillations in the laser intensity can be seen as sidebands on both sides of the main laser line. In this context, a communication system by using a relaxation oscillation frequency as an information carrier is proposed in this paper. The experimental setup is based on operation principle of direct detection, where the obtained microwave signal at the output of a fast photodetector is located on C band and it is modulated with an analog NTSC TV signal.