Search results for "ELECTRONICS"

Typical Aspects of the Microwave Noise Performance of HEMTs at Decreasing Temperatures

1996

In analog signal processing at microwave frequencies the noise performance of active devices is of fundamental importance for the accurate design of low-noise amplifiers. To this aim, the determination of the four noise parameters F O , Γ O (complex variable) and Rn has to be accomplished together with the usual scattering parameter measurements vs. frequency. In addition, the dependence of the device performance vs. temperature is of interest for circuit applications characterized by harsh environmental conditions. In this work the noise behavior of high electron mobility transistors has been investigated by means of measurements and modeling in the 2-18 GHz frequency range and as a functi…

Electrooptical Chromophores for Nonlinear Optical and Photorefractive Applications

1999

Wavelength tuning of femtosecond pulses generated in nonlinear crystals by using diffractive lenses

2010

We demonstrate that diffractive lenses (DLs) can be used as a simple method to tune the central wavelength of femtosecond pulses generated from second-order nonlinear optical processes in birefringent crystals. The wavelength tunability is achieved by changing the relative distance between the nonlinear crystal and the DL, which acts in a focusing configuration. Besides the many practical applications of the so-generated pulses, the proposed method might be extended to other wavelength ranges by demonstrated similar effects on other nonlinear processes, such as high-order harmonic generation.

Scaling guidelines of a soliton-based power limiter for 2R-optical regeneration applications

2010

International audience; In this work, we report scaling rules for the design of an all-fibered soliton-based power limiter for reamplification and reshaping (2R) regeneration process. In particular, we propose general guidelines to fix the optimum fiber length and initial power of the regenerator. We quantitatively point out the optical power limiting effect of the device enabling a significant reduction of the amplitude jitter of a degraded signal. Influence of the initial level of amplitude jitter is discussed and the results are compared with a self-phase modulation-based configuration working in the normal dispersion regime. Realistic numerical simulations in the context of 160 Gbit/s s…

Design of All-Normal Dispersion Microstructured Optical Fiber on Silica Platform for Generation of Pulse-Preserving Supercontinuum Under Excitation a…

2017

We investigated numerically the possibility of all normal dispersion fiber design for near-infrared supercontinuum generation based on a standard air-silica microstructure. The design procedure includes finding of target dispersion profile and subsequent finding of appropriate geometrical fiber design by inverse dispersion engineering. It was shown that the tailoring of dispersion profile could increase the spectral width of generated supercontinuum while maintaining perfect spectral flatness. Conditions necessary for wide and flat supercontinuum generation as well as restrictions imposed by chosen materials were discussed. As a result of design and optimization procedure, an air-silica des…

Polarization attraction using counter-propagating waves in optical fiber at telecommunication wavelengths

2008

International audience; In this work, we report the experimental observation of a polarization attraction process which can occur in optical fibers at telecommunication wavelengths. More precisely, we have numerically and experimentally shown that a polarization attractor, based on the injection of two counter-propagating waves around 1.55 mu m into a 2-m long high nonlinear fiber, can transform any input polarization state into a unique well-defined output polarization state.

Advances in photonic reservoir computing

2017

We review a novel paradigm that has emerged in analogue neuromorphic optical computing. The goal is to implement a reservoir computer in optics, where information is encoded in the intensity and phase of the optical field. Reservoir computing is a bio-inspired approach especially suited for processing time-dependent information. The reservoir’s complex and high-dimensional transient response to the input signal is capable of universal computation. The reservoir does not need to be trained, which makes it very well suited for optics. As such, much of the promise of photonic reservoirs lies in their minimal hardware requirements, a tremendous advantage over other hardware-intensive neural net…

Q-switched mode locking noise-like pulse generation from a thulium-doped all-fiber laser based on nonlinear polarization rotation

2021

Abstract Q-switched mode locking (QML) noise-like pulse (NLP) emission from an all-fiber thulium-doped laser based on the nonlinear polarization rotation effect is reported. The QML emission is obtained in a cavity with net anomalous dispersion in a pump power interval in between the CW laser threshold and the threshold of the NLP regime. Highest-energy QML pulses were observed with a repetition rate of 812 kHz with a pump power of 520 mW at the optical wavelength of 1881.09 nm. A maximum overall energy of 460 nJ at an average output power of 6.4 mW was reached, which corresponds to a burst of mode-locked noise-like sub-pulses with 8.7 ns of pulse duration within a QML envelope of 11 µs. Th…

Wormlike Polystyrene Brushes in Thin Films

1997

Mono- and multilayer films were prepared on mica by solution casting of a high molecular weight polymacromonomer, i.e., a polymethacrylate of about 1000 repeating units each of which was substituted by a polystyrene chain with a molecular weight of about 5000 Da. The films were studied by tapping scanning force microscopy. The material showed a remarkable preference for forming well-defined monolayers of a thickness of 6.5 ± 0.2 nm consistent with the hard core diameter of the collapsed cylindrical brush molecules. When the films were probed with high normal force, the single molecules were observed to organize in a dense nematic-like packing as expected for inherently stiff molecules. In o…

A Comparative Analysis of Residual Block Alternatives for End-to-End Audio Classification

2020

Residual learning is known for being a learning framework that facilitates the training of very deep neural networks. Residual blocks or units are made up of a set of stacked layers, where the inputs are added back to their outputs with the aim of creating identity mappings. In practice, such identity mappings are accomplished by means of the so-called skip or shortcut connections. However, multiple implementation alternatives arise with respect to where such skip connections are applied within the set of stacked layers making up a residual block. While residual networks for image classification using convolutional neural networks (CNNs) have been widely discussed in the literature, their a…