Top PDF A Fundamental Approach to Phase Noise Reduction in Hybrid Si/III-V Lasers

A Fundamental Approach to Phase Noise Reduction in Hybrid Si/III-V Lasers

A Fundamental Approach to Phase Noise Reduction in Hybrid Si/III-V Lasers

Frequency noise PSD: Lasers are pumped CW by an ILX Lightwave LDX-3620 Ultra Low Noise Current Source (battery-powered). Light is collected at the output facet of the laser by a lensed single-mode fiber. There are two fiber isolators about 1 m from the laser facet. The signal is amplified by an optical amplifier (ThorLabs BOA 1004) pumped by a custom battery-powered current source made by Arseny Vasilyev (Chipset: Wavelength Electronics LDD400-1P), with a polarization controller before the amplifier tuned for maximum output. The light is passed through a custom fiber Mach-Zehnder interferometer (FSR 847 MHz). The MZI output is split between two photodetectors: an HP 11982A Lightwave Converter Photodetector for the signal and a ThorLabs PDA10CF for feedback. The optical power incident on the HP photodetector (the signal) is attenuated by a variable attenuator (JDS Fitel HA9) such that the maximum power out of the interferometer is just below photodetector saturation. The MZI fringes are measured on an oscilloscope (Tektronix TDS 3032B) to deter- mine the frequency-to-amplitude gain of the interferometer and the quadrature point. The center frequency of the laser is locked in quadrature by locking the PDA10CF photocurrent to an adjustable reference using a custom battery- powered feedback circuit made by Arseny Vasilyev. RF spectra are measured on an Agilent 4395A RF Spectrum Analyzer set to “sample” detection.
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High-Coherence Hybrid Si/III-V Semiconductor Lasers

High-Coherence Hybrid Si/III-V Semiconductor Lasers

The relentlessly increasing demand for network bandwidth, driven primarily by In- ternet -based services such as mobile computing, cloud storage and video-on-demand, calls for more efficient utilization of the available communication spectrum, as that afforded by the resurging DSP-powered coherent optical communications. Encoding information in the phase of the optical carrier, using multilevel phase modulation formats, and employing coherent detection at the receiver allows for enhanced spec- tral efficiency and thus enables increased network capacity. The distributed feedback semiconductor laser (DFB) has served as the near exclusive light source powering the fiber optic, long-haul network for over 30 years. The transition to coherent commu- nication systems is pushing the DFB laser to the limits of its abilities. This is due to its limited temporal coherence that directly translates into the number of different phases that can be imparted to a single optical pulse and thus to the data capacity. Temporal coherence, most commonly quantified in the spectral linewidth ∆ν, is lim- ited by phase noise, result of quantum-mandated spontaneous emission of photons due to random recombination of carriers in the active region of the laser.
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Frequency Noise Control of Heterogeneous Si/III V Lasers

Frequency Noise Control of Heterogeneous Si/III V Lasers

As discussed in Section 5.1, the technological remedy that could be used to improve the laser’s stability against external reflections included the use of an active material with a low linewidth enhancement factor. Quantum-dot-based semiconductor lasers should show high resistance against external reflections. For example, the InAs/GaAs quantum-dot system near the 1.3 𝜇m showed high endurance against external feedback [90]. However, quantum-dots remain difficult to grow for certain materials and wavelengths. The demonstration of the improvement of the feedback sensitivity in our lasers illustrates that this approach of utilizing the high-reflectivity mirrors, enabled by the reduction of the intrinsic loss of the laser, can be applied to any lasers with a different material system to increase resistance against external feedback. Combined with the use of the low linewidth enhancement factor, this approach will create a laser which can further withstand external reflections.
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An Optimized Hybrid Filter designing for Speckle and Gaussian Noise Reduction in Ultra Sound Images

An Optimized Hybrid Filter designing for Speckle and Gaussian Noise Reduction in Ultra Sound Images

In this work total five images are used for implementation i.e. Lena, Cameraman, Monarch, House and Ultrasound Image. This section defines the results in the form of graphs that are obtained after implementing the proposed work. The parameters are selected on the basis that filter coefficients should be those which provide more PSNR and less MSE. The performance is measured in terms of PSNR, SSIM, fitness, MSE and BER shown in Table 1 and Table 2. The plots for these parameters in case of speckle as well as Gaussian noise are shown in Fig 5, Fig 6, Fig 7, Fig 8 and Fig 9.Then for the purpose of proving the proficiency of proposed work, the contrast is portrayed among the present study, algorithm given by Liu [14] and traditional work [2]shown in Table 3.
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Noise Reduction for Instance-Based Learning with a Local Maximal Margin Approach

Noise Reduction for Instance-Based Learning with a Local Maximal Margin Approach

In this paper we present a novel approach to noise reduction based on local Support Vector Ma- chines (LSVM) which brings the benefits of maximal margin classifiers to bear on noise reduction. This provides a more robust alternative to the majority rule on which almost all the existing noise reduction techniques are based. Roughly speaking, for each training sample an SVM is trained on its neighbour- hood and if the SVM classification for the central sample disagrees with its actual class there is evidence in favour of removing it from the training set. We provide an empirical evaluation on 15 real datasets showing improved classification accuracy when using training data edited with our method as well as specific experiments regarding the spam filtering application domain. We present a further evaluation on two artificial datasets where we analyse two different types of noise (Gaussian sample noise and mislabelling noise) and the influence of different class densities. The conclusion is that LSVM noise reduction is significatively better than the other analysed algorithms for real datasets and for artificial datasets perturbed by Gaussian noise and in presence of uneven class densities.
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Characterization of 6 1 Å III V materials grown on GaAs and Si: a comparison of GaSb/GaAs epitaxy and GaSb/AlSb/Si epitaxy

Characterization of 6 1 Å III V materials grown on GaAs and Si: a comparison of GaSb/GaAs epitaxy and GaSb/AlSb/Si epitaxy

and dark current measurements, GaSb p-i-n structures grown on GaAs and Si substrates using IMF.. arrays were compared with an equivalent structure grown lattice matched on native GaSb..[r]

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Performance Evaluation of III-V Hetero/Homojunction Esaki Tunnel Diodes on Si and Lattice Matched Substrates

Performance Evaluation of III-V Hetero/Homojunction Esaki Tunnel Diodes on Si and Lattice Matched Substrates

Previous reports have indicated some sensitivity to i -layer design for Esaki diode performance in the BG diode systems [50]. This section investigates the substitution of the i -layer from InAs to GaSb. Fig. 6.44 shows schematics representing the devices tested in this series. Changes with respect to BG-TD2 include: Te substituted for Si as the n-type dopant, substrates are now on miss cut wafers, InAs thickness has been slightly reduced, and the i -layer consists of GaSb. Te does not have the same counterdoping problems as Si, but the dopings levels are not so high as to expect dopant species to be much of an issue. Changing to miss cut wafers is theorized to be better for epitaxy, but prior results from this study do not appear to exhibit any impact due to this change. Thinner InAs should reduce the likelihood of problems associated with critical thickness from appearing. Changing to GaSb from InAs in the i -layer may affect performance due to the more extreme bending seen in GaSb, but the tunnel region for the BG diodes is larger than the i -layer and may show little or no impact on J P and J V .
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Blame Based Noise Reduction: An Alternative Perspective on Noise Reduction for Lazy Learning

Blame Based Noise Reduction: An Alternative Perspective on Noise Reduction for Lazy Learning

The BBNRv1 algorithm worked well for the case-based spam filtering problem and resulted in a conservative reduction of the number of cases in the spam case-base removing, on average, not more than 5% of the cases (Delany and Cunningham, 2004). Our evaluation of this algorithm on other datasets indicated that the number of cases being removed by BBNRv1 was much higher on these other datasets. Up to 57% of cases were removed from one dataset and the average percentage of cases removed across all 20 datasets evaluated was 25%. For this reason a more conservative deletion policy was devised which we call BBNRv2. The competence model built at the start of the noise reduction process is static in BBNRv1. Once a case is removed from the case-base, the liability sets for other cases do not reflect this change. BBNRv2 updates the liability set competence model after each case is removed. The effect of this is that, if the removal of a case results in a previously misclassified case m now being correctly classified, any other cases which contributed to that misclassification have their liability sets updated to indicate that m is no longer an element.
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Investigations on the V(III) Reduction Process of All-Vanadium Redox Flow Battery

Investigations on the V(III) Reduction Process of All-Vanadium Redox Flow Battery

dissolved in sulfuric acid. Although the overall cell performance depends on various factors [6], the negative and positive electrode reactions are the most important ones to optimize the cell operation and to realize high energy efficiency. Up to now, the electrochemistry performance and electrode processes of positive redox couple in VRFB have been investigated extensively. Among them, Gattrell et al. [7] reported that the reduction of V(V) to V(IV) proceeds by CEC mechanisms at low overpotentials and by ECC mechanisms at high overpotentials. Oriji et al. [8, 9] studied the stokes radii of V(IV) and V(V) species in concentrated sulfuric acid solutions and further discussed the electrochemical behavior of positive electrolytes. Xu et al. [10] studied the electrochemical behavior of the V(IV)/V(V) couple on a graphite electrode at different temperatures and found the anodic oxidation of V(IV) is a mixed kinetic-diffusion controlled process at the anodic polarization ranged from 32 to 132 mV. Wen et al. [11] investigated the electrode process of concentrated V(IV)/V(V) species, and they found the electrode process was affected significantly by the sulfuric acid concentration. The electrode process of V(IV)/V(V) is controlled by the electrochemical polarization and diffusion in H 2 SO 4 solution below
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TWO-PHASE C-MEANS CLUSTERING WITH NOISE REDUCTION USING FUZZY RULES

TWO-PHASE C-MEANS CLUSTERING WITH NOISE REDUCTION USING FUZZY RULES

International Journal of Advance Research In Science And Engineering http://www.ijarse.com IJARSE, Vol. No.3, Issue No.11, November 2014 ISSN-2319-8354(E) these methods are having some disadvantages, thatnoise in spatial feature creeps into miss classification of data. Noiseless data are changed unnecessarily by the inference calculations in defuzzification. It results in blurred output image.In order to rectify these drawbacks, this paper introduces (i) a new mask to filter the noise in spatial information, (ii) a new clustering method based on the standard FCM, and (iii) a new defuzzification method.
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Pulses on Demand in Fibre and Hybrid Lasers

Pulses on Demand in Fibre and Hybrid Lasers

The high modulation bandwidth of high-power diode lasers that are used for pumping the laser system allows for the gain switching technique [8] to [10] to be used, where we can achieve good control over the pulse-generation dynamics and consequently enable pulse-on-demand operation for nearly single-mode beam quality. The gain-switching technique uses modulation of the pump power (provided by the high- power diode lasers) to select only the first spike of the relaxation oscillations that form a single laser pulse [11]. With precise gain control pulses as short as 28 ns [12] were generated from a ytterbium-doped fibre laser and the achievable (but not limited to) peak power was over 4 kW [13]. Even shorter laser pulses [14] were generated by a more complicated core-pumping scheme in a thulium-doped fibre. Using clad pumping at 790 nm, an efficient system [15] can be realized, which also has the benefit of not being susceptible to the photodarkening effect [16], which usually causes problems in highly pumped fibre lasers.
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Hyperspectral Data Dimensionality Reduction Using Hybrid Approach

Hyperspectral Data Dimensionality Reduction Using Hybrid Approach

information. This abundance of data is hard to exploit due to high computational cost involved in processing this data. Dimensionality reduction deals with transforming high dimensional data in to lower dimensional space without losing significance of the High dimensional data. In this paper, a new methodology has been proposed that is based on existing algorithms. This model uses the advantages of PCA, ICA, and MNF to reduce dimensionality with high classification accuracy. Traditional AVIRIS Indian Pine benchmark dataset has been used for experiment. ENVI is used for dimension reduction. ERDAS Imagine has been used for Classification using Maximum likelihood method.
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Kinetic modelling of fundamental (00̊1) and sequence (00̊2) band CO₂ lasers

Kinetic modelling of fundamental (00̊1) and sequence (00̊2) band CO₂ lasers

^’barrier" which inhibits electrons from attaining very high energies at normal E/P. Thus mixtures with a high molecular content are characterised by lower average electron energies, resulting in a smaller population of electrons capable of single-step dissociation. To test this explanation, small amounts of CO and ‘O^ were added to the 13:9:78 mixture; since these additives also possess large in­ elastic cross-sections, a further decrease in dissociation rate could be expected. As shown in figure 3.1, this was in fact the case, and the addition of 5% CO or 0^ approximately halved the dissociation rate at constant E/P. This result has interesting implications for CO^ dissociation levels in sealed-off lasers, suggesting that as dissoc­ iation proceeds, an equilibrium CO^ level will quickly be reached since the dissociation products will have the effect of (a) re-forming COg by reactions like C3.4) and (3.5), and (b) inhibiting the dis­ sociation rate by reducing the average discharge electron energy. The suggestion is supported by routine observations in sealed-off lasers that a dissociation equilibrium is reached within a few seconds of switching on the discharge current.
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Two dimension MDW OCDMA code cross-correlation for reduction of phase induced intensity noise

Two dimension MDW OCDMA code cross-correlation for reduction of phase induced intensity noise

floor. Bit rate or data rate is a measure of a number of bits transmitted per second over a fiber channel. Bit rate reflects the information carrying capacity of a fiber communications link. High data rate will increase the BER and deteriorate the system performance. Noise power is the noise interference that exists in the system other than the desired signal. he wavelength-time code cross-correlation is generated differently compared to the 1-D OCDMA code[9].

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in Health Phase III (CCH III)

in Health Phase III (CCH III)

Our smaller member states are faced with problems of retention of trained personnel, the quality, skills and competencies of the existing health workforce, as well as limitations in capacity to train a health workforce to meet their needs. This includes the full extent of the health workforce such as nurses, physician, public health practitioners, researchers and health care managers. This is also mirrored at CARICOM level. Our vision aims to provide access to quality health services for all people of the CARICOM Region through the strengthening of health human resources. The strategic direction laid out in the CCH III aims to mobilise institutional actors at the national, regional and global levels of the health and related sectors and other relevant civil society actors, to collectively strengthen the human resources in health through policies, interventions, and networks. We have incorporated strategies to mitigate against the effects of regional and international labour force challenges but to also embrace the potential opportunities presented by the regional and global trends. Our response supports the Toronto Call to Action (2006) and is designed to specifically address the Millennium Development Goals in accordance with national health priorities.
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Threshold characteristics and intensity fluctuations of lasers with excess quantum noise

Threshold characteristics and intensity fluctuations of lasers with excess quantum noise

In lasers with nonorthogonal transverse eigenmodes the spontaneous-emission noise in the laser mode is enhanced by the transverse excess-noise factor, or K factor @ 1–12 # . Ex- perimental values of transverse K factors realized in unstable cavities range from K 5 200 to 500 @ 2,6,7 # . The longitudinal K factor, which arises due to nonorthogonality of the longi- tudinal eigenmodes, usually stays close to unity @ 11,12 # . So far, all studies of the K factor, both theoretically and experi- mentally, have concentrated on its consequences for the laser phase noise. In this paper we investigate, both theoretically and experimentally, the appearance of K in the intensity noise. This automatically brings up the laser threshold char- acteristics, being intimately linked to intensity noise. In our analysis we include bad-cavity aspects since, in practical cases, excess noise occurs in lasers with relatively large losses, so that the cavity bandwidth often exceeds the gain bandwidth @ 13 # .
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Noise reduction in digital images

Noise reduction in digital images

This research project has resulted in the development of a noise reduction technique which can be used to decrease the visible noise in images taken using exposure times greater than 1/4 second. Using this noise reduction technique, people who have taken images in low-light situations are able to take advantage of the many benefits of digital photography. Digital photography allows nearly instantaneous access to the images; image dissemination is accomplished quickly across the Internet; and image modifications can be done quickly. In addition to saving money by eliminating the need for film and film developing, some digital cameras have an LCD display panel for instant image review. (3) This feature eliminates the need to take multiple pictures of an event to ensure its capture.
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The Benefits and Costs of Noise Reduction

The Benefits and Costs of Noise Reduction

This article tries to measure in a Cost-Benefit Analysis a stricter noise abatement program originated from traffic roads in Israel. Using hedonic prices method of three large cities and rural areas transactions, the benefit from noise reduction was found. In order to perform a social cost benefit analysis a measure of benefit was derived for a one kilometer of road and was compared with the cost of noise reduction under different assumptions of road structure. The results indicate that even tough benefits were largely increased from past decade (e.g., 1.4% of an average urban property value per 1 decibal reduction), the decision to insulate a given road is dependent on location and road structure. This raises the normative question of a national vs. regional standards that decision-makers should be aware of and such studies could be of help in this regard.
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Dislocation reduction of InAs nanofins prepared on Si substrate using metal organic vapor phase epitaxy

Dislocation reduction of InAs nanofins prepared on Si substrate using metal organic vapor phase epitaxy

indicated that a threading dislocation density above 10 7 cm − 2 for a 900-nm-thick epilayer decreased to 10 6 cm − 2 due to the self-annihilation of dislocations when the film thickness was increased to more than 4 μm for a III-V epi- layer deposited on a Si substrate [8,18]. A III-V epilayer on a miscut Si (001) substrate has fewer threading disloca- tions and antiphase domain boundaries than those of an epilayer on an untilted Si (001) substrate [6,17]. Previous studies have attempted to reduce the dislocation density for a III-V epilayer deposited on a Si (001) substrate using methods such as thermal cycle annealing and the utilization of short-period strained intermediate-layer superlattices [6-10]. During thermal cycle annealing treatment, an epilayer is subjected to large temperature oscillations and thus periodically switches between the compressed and tensile states, reversing the motion of the dislocations. However, thermal cycle annealing processes are time-consuming. Strained intermediate-layer superlat- tices effectively decrease the threading dislocation density by generating additional stress, but their insertion leads to poor reproduction. In previous reports, the density of dis- locations in an epilayer deposited on a planar Si substrate could be decreased by about two orders of magnitude by mixed thermal cycle annealing steps and strained intermediate-layer superlattice epitaxial growth processes [6-10]. An alternative technology for effectively reducing dislocation density is a kind of selective epitaxial growth
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Constructing magnetic Si C Fe hybrid microspheres for room temperature nitroarenes reduction

Constructing magnetic Si C Fe hybrid microspheres for room temperature nitroarenes reduction

Representative TEM images of Si-C-Fe hybrid microspheres are shown in Fig. 8. Compared with Fc-PDVB microspheres (Fig. 1b), the size of the pyrolyzed samples became smaller because of sharp shrinkage during the transformation of the organic network of Fc-PDVB microspheres to organic-inorganic Si-C-Fe hybrid microspheres. In addition, nanoscale Fe-rich region (diameter of ~10 nm) is evident in the higher magnification TEM image. The measured d (110) spacing of Fe is 0.203 nm that is consistent with the value obtained from XRD measurement and the literature. This further confirms the presence of Fe 0 . The nitrogen physisorption measurements of the pyrolyzed microspheres in Fig. 9 exhibit a type I isotherm, which is typical for nano- and meso-porous structures with a specific surface area of 347.9 m 2 g -1 . A large nitrogen uptake at low relative pressure (p/p 0 < 0.05) indicates the presence of
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