High intensity behavior of pyroelectric photorefractive self-focusing in LiNbO3

International audienceThe formation of self-confined beams using pyroelectric effect is numerically and experimentally studied in photorefractive LiNbO3. For a given crystal temperature change, the trapped beam width is shown to be less efficient as intensity is increased. Numerical calculations reveal that the induced refractive-index profile varies along propagation for large intensities due to a nonlinear photovoltaic effect. Moreover, it eventually gives beam splitting for intensities greater than a threshold intensity that depends on LiNbO3 composition

Time-domain dynamics and stability analysis of optoelectronic oscillators based on whispering-gallery mode resonators

International audienceOptoelectronic oscillators (OEOs) are microwave photonics systems intended to generate ultrastable radio-frequency signals with unprecedented phase noise performance for aerospace and communication engineering applications. They had originally been introduced in a configuration where the energy storage element was a fiber delay line. However, recent research in view of size and power consumption optimization has led to novel configurations where this fiber delay line is replaced by an ultrahigh Q whispering-gallery mode (WGM) resonator. So far, there has been no theoretical framework enabling to understand the dynamical behavior of these new architectures of OEOs. In this paper, we propose for the first time a deterministic time-domain model to investigate the dynamics of these OEOs based on WGM resonators. This model enables us to perform the stability analysis of the microwave oscillations, and to determine rigorously their range of stability as the loop gain is varied. After building the model, we perform a full stability analysis of the various stationary solutions for the microwave output. We then perform extensive numerical simulations, which are in complete agreement with the stability analysis. The theoretical analysis is also found to be in excellent agreement with our experimental measurements

120 km single-photon Brillouin optical time domain reflectometry

We present a novel distributed Brillouin optical time domain reflectometer (BOTDR) using standard telecommunication fibers based on single-photon avalanche diodes (SPADs) in gated mode, hd-BOTDR, with a range of 120 km and 10 m spatial resolution. We experimentally demonstrate the ability to perform a distributed temperature measurement, by detecting a hot spot at 100 km. Instead of using a frequency scan like conventional BOTDR, we use a frequency discriminator based on the slope of a fiber Bragg grating (FBG) to convert the count rate of the SPAD into a frequency shift. A procedure to take into account the FBG drift during the acquisition and perform sensitive and reliable distributed measurements is described. We also present the possibility to differentiate strain and temperature

The role of green finance, eco-innovation, and creativity in the sustainable development goals of ASEAN countries

Recently, sustainable development has become a global requirement. Every country strives to achieve this essential goal, and this attracts the attention of researchers and policymakers. This study investigates the impact of green finance, eco-innovation, and creativity on the sustainable development goals in ASEAN countries. Using CUP-FM and CUP-BC techniques, the study examines the association between variables, and finds that green finance (such as green credit), renewable energy production, eco-innovation, and creativity, have positive associations with sustainable development goals. The control variable, economic growth, has a negative association with sustainable development goals. Based on the evidence, the ASEAN region must increase the quantity of green bonds as a part of green finance. This financial measure would guarantee adequate returns for private investors

A Schrödinger Equation for Evolutionary Dynamics

We establish an analogy between the Fokker–Planck equation describing evolutionary landscape dynamics and the Schrödinger equation which characterizes quantum mechanical particles, showing that a population with multiple genetic traits evolves analogously to a wavefunction under a multi-dimensional energy potential in imaginary time. Furthermore, we discover within this analogy that the stationary population distribution on the landscape corresponds exactly to the ground-state wavefunction. This mathematical equivalence grants entry to a wide range of analytical tools developed by the quantum mechanics community, such as the Rayleigh–Ritz variational method and the Rayleigh–Schrödinger perturbation theory, allowing us not only the conduct of reasonable quantitative assessments but also exploration of fundamental biological inquiries. We demonstrate the effectiveness of these tools by estimating the population success on landscapes where precise answers are elusive, and unveiling the ecological consequences of stress-induced mutagenesis—a prevalent evolutionary mechanism in pathogenic and neoplastic systems. We show that, even in an unchanging environment, a sharp mutational burst resulting from stress can always be advantageous, while a gradual increase only enhances population size when the number of relevant evolving traits is limited. Our interdisciplinary approach offers novel insights, opening up new avenues for deeper understanding and predictive capability regarding the complex dynamics of evolving populations