Design Of All-Normal Dispersion With Ge11.5As24Se64.5/Ge20Sb15Se65 Chalcogenide PCF Pumped At 1300nm For Supercontinuum Generation

Supercontinuum spectrum generation is a process in which laser beam in femtoseconds and high power (kilowatts) is converted into a broad-spectrum beam of light after passing through a specific environment. Of course, achieving this range comes with many limitations. In this paper, photonic crystal fibers are used as a substrate for input pulse due to the ability to control dispersion and loss, and creating single-mode operating conditions. One of the main factors for the formation of supercontinuum spectra of injection pulses is maintaining the nonlinear performance of this type of fiber by controlling the effective mode area and also using chalcogenides (nonlinear coefficients about 100 times higher than silica) in their structure. In the proposed structure, a photonic crystal fiber with silica base element and air cavities with hexagonal structure with the center of Ge11.5As24Se64.5 chalcogenide element have been used to provide the nonlinear property of the structure. Also, in this structure, a ring of Ge20Sb15Se65 chalcogenide elements has been used to reduce the effective mode region and create a flat dispersion curve at a wavelength of 1300 nm (second telecommunication window). The input pulse power is 10 kW and its width is 50 femtoseconds, which has caused the range of the supercontinuum from 800 nm to 1900 nm. This structure can be used to provide the required wavelengths as a carrier in a wavelength division multiplexing (WDM).

Estimation and Analysis of Higher-Order Harmonics in Advanced Integrated Circuits to Implement Noise-Free Future-Generation Micro- and Nanoelectromechanical Systems

This work deals with the analysis of spectrum generation from advanced integrated circuits in order to better understand how to suppress the generation of high harmonics, especially in a given frequency band, to design and implement noise-free systems. At higher frequencies, the spectral components of signals with sharp edges contain more energy. However, current closed-form expressions have become increasingly unwieldy to compute higher-order harmonics. The study of spectrum generation provides an insight into suppressing higher-order harmonics (10th order and above), especially in a given frequency band. In this work, we discussed the influence of transistor model quality and input signal on estimates of the harmonic contents of switching waveforms. Accurate estimates of harmonic contents are essential in the design of highly integrated micro- and nanoelectromechanical systems. This paper provides a comparative analysis of various flip-flop/latch topologies on different process technologies, i.e., 130 and 65 nm. An FFT plot of the simulated results signifies that the steeper the spectrum roll-off, the lesser the content of higher-order harmonics. Furthermore, the results of the comparison illustrate the improvement in the rise time, fall time, clock-Q delay and spectrum roll-off on the better selection of slow-changing input signals and more accurate transistor models.

Effective frequency estimation method for sinusoidal interference in seismic data

The removal of sinusoidal interference is an important step in seismic data processing, especially for data with low signal-to-noise ratios. The intermittent character of sinusoidal interference makes it challenging to identify and attenuate. To address this issue, we propose a method to accurately identify sinusoidal interference and rapidly estimate its frequencies. A spectrum-generation strategy is presented to generate an amplitude spectrum with noticeable sinusoidal interference. An initial estimate of the affected frequencies is found using a frequency-search technique based on the amplitude spectrum. The estimate is then refined by an iterative frequency estimation algorithm, which includes fast frequency estimation and normalized cross-correlation calculation. After modeling the noise using the precise frequency estimation, the sinusoidal interference in seismic data can then be suppressed by adaptively subtracting the estimated noise from the raw seismic data. The effectiveness of the proposed method in identifying sinusoidal interference is verified by testing it on synthetic and field data and by comparing the results with those from existing methods. Synthetic and real data examples indicate that the method is most applicable to land seismic data.

PyAtomDB: Extending the AtomDB Atomic Database to Model New Plasma Processes and Uncertainties

The AtomDB project provides models of X-ray and extreme ultraviolet emitting astrophysical spectra for optically thin, hot plasma. We present the new software package, PyAtomDB, which now underpins the entire project, providing access to the underlying database, collisional radiative model calculations, and spectrum generation for a range of models. PyAtomDB is easily extensible, allowing users to build new tools and models for use in analysis packages such as XSPEC. We present two of these, the kappa and ACX models for non-Maxwellian and Charge-Exchange plasmas respectively. In addition, PyAtomDB allows for full open access to the apec code, which underlies all of the AtomDB spectra and has enabled the development of a module for estimating the sensitivity of emission lines and diagnostic line ratios to uncertainties in the underlying atomic data. We present these publicly available tools and results for several X-ray diagnostics of Fe L-shell ions and He-like ions as examples.

Numerical Analysis of Supercontinuum Generated Microstructured Optical Fiber with all Normal Chromatic Dispersion

A micro-structured photonic crystal fiber (M-PCF) with all normal chromatic dispersion has been proposed for supercontinuum spectrum generation which is applicable in optical transmission and optical coherence tomography applications. Calculations of its different properties using finite difference method have shown that the proposed M-PCF has a high nonlinear coefficients at 1.06 μm, 1.30 μm and 1.55 μm wavelength with flattened chromatic dispersion, low confinement losses and broad supercontinuum spectrum. Moreover, it has been shown that the proposed design obtain high power and short fiber length at 1.06 μm, 1.30 and 1.55 μm center wavelengths by propagating sech2 picosecond optical pulses with 1.0 ps pulse width at a full width at half maximum.