Photocarrier escape time in quantum-well light-absorbing devices: Effects of electric field and well parameters

We analyze the dependence of the carrier escape time from a single-quantum-well optoelectronic device on the aplied electric field and well width and depth. For this purpose, a new simple and computationally efficient theory is developed. This theory is accurate in the case of electrons, and the assessment of the applicability for holes is given. Semi-analytical expressions for the,escape times are derived. Calculations are compared to experimental results and previous numerical simulations. Significant correlations between the Position,of quantum-well energy levels and the value of the escape time are found. the main escape mechanism At room temperature is established to be thermally assisted tunneling/emission through near-barrier-edge states. The formation of a new eigenstate in the near-barrier-edge energy region is found to reduce the electron escape time significantly, which can be used for practical device optimization

Quantum-well design for monolithic optical devices with gain and saturable absorber sections

We propose a new design of semiconductor quantum-well heterostructures, which can be used to improve the performance of monolithic mode-locked diode lasers and all-optical signal-processing devices with gain and saturable absorber sections. Numerical modeling shows that this design can increase the carrier sweep-out rate from the absorber section by several orders of magnitude, while retaining high carrier confinement on the ground level making for efficient signal amplification by the gain sections

The Role of Constraints in a Segregation Model: The Symmetric Case

In this paper we study the effects of constraints on the dynamics of an adaptive segregation model introduced by Bischi and Merlone (2011). The model is described by a two dimensional piecewise smooth dynamical system in discrete time. It models the dynamics of entry and exit of two populations into a system, whose members have a limited tolerance about the presence of individuals of the other group. The constraints are given by the upper limits for the number of individuals of a population that are allowed to enter the system. They represent possible exogenous controls imposed by an authority in order to regulate the system. Using analytical, geometric and numerical methods, we investigate the border collision bifurcations generated by these constraints assuming that the two groups have similar characteristics and have the same level of tolerance toward the members of the other group. We also discuss the policy implications of the constraints to avoid segregation

Dynamic modal analysis of monolithic mode-locked semiconductor lasers

We analyze the advantages and applicability limits of the mode-coupling approach to active, passive, hybrid, and harmonic mode-locking in diode lasers. A simple, computationally efficient numerical model is proposed and applied to several traditional and advanced laser constructions and regimes, including high-frequency pulse emission by symmetric and asymmetric colliding pulse mode-locking, and locking properties of hybrid modelocked Fabry–Perot and distributed Bragg reflector lasers

Calculation of homoclinic and heteroclinic orbits in 1D maps

Abstract Homoclinic orbits and heteroclinic connections are important in several contexts, in particular for a proof of the existence of chaos and for the description of bifurcations of chaotic attractors. In this work we discuss an algorithm for their numerical detection in smooth or piecewise smooth, continuous or discontinuous maps. The algorithm is based on the convergence of orbits in backward time and is therefore applicable to expanding fixed points and cycles. For simplicity, we present the algorithm using 1D maps

Low saturation fluence in a semiconductor saturable electroabsorber mirror operated in a self-biased regime

A semiconductor saturable absorber mirror utilizing the electroabsorption effect on a self-biased stack of extremely shallow quantum wells is proposed and analyzed theoretically and numerically. The saturation flux and recovery time of the proposed device when operated with picosecond incident pulses are shown to compare very favorably with existing all-optical constructions. (C) 2008 American Institute of Physics

Electrical Stimulation of Rhabdomyosarcoma Cells Induces Cell Cycle Arrest and Autophagy

Rhabdomyosarcoma is a family of rare juvenile cancers that express molecular factors implicated in myogenic differentiation. Cell cycle arrest is absolutely necessary for muscle maturation, while abnormal cell cycle and cell death programs are hallmarks of cancer onset and progression. The cancerous rhabdomyosarcoma cells continue to uncontrollably proliferate in part due to deficiencies in the myogenic program. Electrical stimulation is known to alter the phenotype of myogenic cells, such changes include cell cycle arrest and enhanced myoblast differentiation. Since rhabdomyosarcoma tumors are muscle-like this thesis looks at the use electrical stimulation towards these cells in an attempt to induce differentiation and prevent growth. The results indicate that the response elicited in rhabdomyosarcoma cells following electrical stimulation is different from the one observed in myoblasts, however cell cycle arrest and cell death through autophagy contribute to a large reduction in the number of cells, which represents a potential therapeutic approach

Racism in Modern Russia

In October 2013, one of the largest anti-migrant riots took place in Moscow. Clashes and arrests continued late into the night. Some in the crowd, which grew to several thousand people, could be heard chanting “Russia for the Russians” with their animus directed towards dark-skinned labor migrants from the southern border. The slogan “Russia for the Russians” is not a recent invention. It first gained notoriety in the very last years of the tsarist regime, appealing primarily to individuals drawn to the radical right. Analyzing a wide range of printed and visual sources, Racism in Modern Russia marks the first serious attempt to understand the history of racism over a span of 150 years. A brilliant examination of the complexities of racism, Eugene M. Avrutin’s panoramic book asks powerful questions about inequality and privilege, denigration and belonging, power and policy, and the complex historical links between race, whiteness, and geography. The ebook editions of this book are available open access under a CC BY-NC-ND 4.0 license on www.bloomsburycollections.com

Tunable operation of a gain-switched diode laser by nonresonant self-injection seeding

In this letter, we report tunable operation of a gain-switched diode laser by nonresonant self-injection seeding from an uncoated glass slide used as an external cavity reflector. A spectral linewidth reduction from 11 to 0.05 nm has been achieved for picosecond pulses with little effect on other laser characteristics. Good agreement with numerical simulations based on a compound-cavity laser model is also reported