330 research outputs found
Quantum fluctuations in multimode semiconductor lasers
No full textWe derive a quantum macroscopic model for a multimode semiconductor laser, starting from a complete microscopic description. Nonlinear gain terms describing saturation and mode-mode interaction are obtained by a suitable treatment of the spectral hole burning in the distribution of carriers. In the case in which there are two neighbouring active longitudinal modes above threshold and for quiet pumping, we calculate the spectrum of the total intensity fluctuations at zero frequency. For moderate pumping level the nonlinear gain terms do not reduce the degree of anticorrelation between modes, leaving the squeezing in total intensity unchanged with respect to the single-mode case. Only for very high pumping does the nonlinear gain suppression become relevant, and the total intensity noise is increased
Noiseless amplification in cavity-based optical systems with an internal two-photon process. II. Self-frequency-doubling laser and second-harmonic generation, self-down-converting laser
No full textEl trabajo educativo de los estudiantes en las instituciones de educación superior
No full textYeldinova S. El trabajo educativo de los estudiantes en las instituciones de educación superior : una vertiente innovadora / O. Bosyi, L. Levytska, L. Cherednyk, I. Protsenko, S. Yeldinova // Revista Eduweb. - 2025. - 19(1). – Р.85–104. https://doi.org/10.46502/issn.1856-7576/2025.19.01.6(en) The article analyzes the innovative system of educational work in an educational institution and proposes innovative approaches to improving the educational sector. The purpose of the article is to reveal the innovative component in the educational system of educational institutions and experimentally verify the effectiveness and importance of the innovative system of educational assistance in higher education institutions for education. The methodological basis of the study is presented at four hierarchically subordinate levels: philosophical, general scientific, specifically scientific and technological. The structural elements of the innovative system of educational assistance in an educational institution, its components, and the main ways of professionalization are developed. We highlight the main innovative principles of education in educational institutions. The main innovative principles and methods of education in educational institutions are highlighted. An experimental study was conducted to confirm the effectiveness and importance of the innovative system of educational work in higher education institutions for education. As a result of the experiment, positive changes allow us to speak about an increase in the level of student learning
Cavity solitons in driven VCSELs above threshold
No full textCSs have been theoretically predicted and recently experimentally demonstrated in broad area, vertical cavity, driven semiconductor lasers (VCSELs) slightly below the lasing threshold. Above threshold, the simple adiabatic elimination of the polarization variable is not correct, leading to oscillatory instabilities with a spuriously high critical wave-number. To achieve real insight on the complete dynamical problem, we study here the complete system of equations and find regimes where a Hopf instability, typical of lasers above threshold, affects the lower intensity branch of the homogeneous steady state, while the higher intensity branch is unstable due to a Turing instability. Numerical results obtained by direct integration of the dynamical equations show that writable/erasable CSs are possible in this regime, sitting on unstable background
Cavity soliton laser based on VCSEL with saturable absorber
No full textWe study theoretically a broad-area vertical cavity surface emitting laser (VCSEL) with a saturable absorber. We show numerically the presence of cavity solitons in the system: they exist as solitary structures formed through a modulationally unstable homogeneous lasing state that coexists with a background with zero intensity. Such a peculiar scenario endows the solitons with unique properties compared to cavity solitons in most previously studied optical systems. In particular, these solitons do not as such rely on a proper phase of the addressing pulses to be either created or deleted. We show that exciting and deleting the solitons depend crucially on whether a threshold in the soliton peak has been reache
Neural Plasticity in Common Forms of Chronic Headaches
No full textHeadaches are universal experiences and among the most common disorders. While headache may be physiological in the acute setting, it can become a pathological and persistent condition. The mechanisms underlying the transition from episodic to chronic pain have been the subject of intense study. Using physiological and imaging methods, researchers have identified a number of different forms of neural plasticity associated with migraine and other headaches, including peripheral and central sensitization, and alterations in the endogenous mechanisms of pain modulation. While these changes have been proposed to contribute to headache and pain chronification, some findings are likely the results of repetitive noxious stimulation, such as atrophy of brain areas involved in pain perception and modulation. In this review, we provide a narrative overview of recent advances on the neuroimaging, electrophysiological and genetic aspects of neural plasticity associated with the most common forms of chronic headaches, including migraine, cluster headache, tension-type headache, and medication overuse headache
Особенности подготовки специалистов пограничного контроля
No full textMakarevich A. A.; Skvortsov D. A.; Protsenko L. N. Features of the training of border control specialist
Searching Malware and Sources of Its Distribution in the Internet
No full textIn the article is considered for the first time developed by the author algorithm of searching malware and sources of its distribution, based on published HijackThis logs in the Internet
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