Complexity of Polarized Spatial Patterns in Large Area Square VCSEL

We consider pattern selection process in a wide aperture VCSEL near threshold. We show that for a square geometry of the laser aperture, the patterns formed at lasing threshold can be very complicated because of a possible misalignment between directions of an intrinsic spatial anisotropy of VCSEL and lateral boundaries of its aperture. The analogy with quantum billiard structures is established, and fingerprints of wave chaos are found. Influence of localized inhomogeneous in the pump current is also considered.Comment: 10 pages, 8 figures, uses REVTEX

Drifting instabilities of cavity solitons in vertical cavity surface-emitting lasers with frequency selective feedback

In this paper we study the formation and dynamics of self-propelled cavity solitons (CSs) in a model for vertical cavity surface-emitting lasers (VCSELs) subjected to external frequency selective feedback (FSF), and build their bifurcation diagram for the case where carrier dynamics is eliminated. For low pump currents, we find that they emerge from the modulational instability point of the trivial solution, where traveling waves with a critical wavenumber are formed. For large currents, the branch of self-propelled solitons merges with the branch of resting solitons via a pitchfork bifurcation. We also show that a feedback phase variation of 2\pi can transform a CS (whether resting or moving) into a different one associated to an adjacent longitudinal external cavity mode. Finally, we investigate the influence of the carrier dynamics, relevant for VCSELs. We find and analyze qualitative changes in the stability properties of resting CSs when increasing the carrier relaxation time. In addition to a drifting instability of resting CSs, a new kind of instability appears for certain ranges of carrier lifetime, leading to a swinging motion of the CS center position. Furthermore, for carrier relaxation times typical of VCSELs the system can display multistability of CSs.Comment: 11 pages, 12 figure

Coupling of polarization and spatial degrees of freedom of highly divergent emission in broad-area square vertical-cavity surface-emitting lasers

The polarization of highly divergent modes of broad-area square vertical-cavity surface-emitting lasers is shown to be only marginally affected by material anisotropies but determined by an interplay of the polarization properties of the Bragg cavity mirrors and of the transverse boundary conditions. This leads to a locking of the polarization direction to the boundaries and its indeterminacy for wave vectors oriented along the diagonal. We point out a non-Poissonian character of nearest-neighbor frequency spacing distribution and the impossibility of single-wave number solutions

Vector-resonance-multimode instability

The modulation and multimode instabilities are the main mechanisms which drive spontaneous spatial and temporal patterns formation in a vast number of nonlinear systems ranging from biology to the laser physics. Using Er-doped fiber laser as a test bed, here for the first time we demonstrate both experimentally and theoretically a new type of a low threshold vector resonance multimode instability which inherits features of multimode and modulation instabilities. The same as for the multimode instability, the large number of longitudinal modes can be excited without modes synchronization. To enable modulation instability, we modulate the state of polarization of the lasing signal with the period of the beat length by adjustment of the in-cavity birefringence and the state of polarization of the pump wave. As a result, we show regimes tunability from complex oscillatory to periodic with longitudinal modes synchronization in the case of the resonance matching between beat and cavity lengths. Apart from the interest in laser physics for unlocking tunability and stability of dynamic regimes, the proposed mechanism of the vector resonance multimode instability can be of fundamental interest for nonlinear dynamics of various distributed systems

Polarization properties in the transition from below to above lasing threshold in broad-area vertical-cavity surface-emitting lasers

For highly divergent emission of broad-area vertical-cavity surface-emitting lasers (VCSELs) a rotation of the polarization direction by up to 90 degrees occurs when the pump rate approaches the lasing threshold. Well below threshold the polarization is parallel to the direction of the transverse wave vector and is determined by the transmissive properties of the Bragg reflectors that form the cavity mirrors. In contrast, near-threshold and above-threshold emission is more affected by the reflective properties of the reflectors and is predominantly perpendicular to the direction of transverse wave vectors. Two qualitatively different types of polarization transition are demonstrated: an abrupt transition, where the light polarization vanishes at the point of the transition, and a smooth one, where it is significantly nonzero during the transition

Progress Towards Achieving SDG 13 «Combating Climate Change» in Belarus

10995/27938В статье рассмотрено такое глобальное изменение в природе как климат. Климат в Беларуси играет важную роль, так как любая его инверсия не обходится без последствий. Так же в данной статье приведены пути решения проблемы, связанной с преобразованием климата.The article examines such a global change in nature as climate. The climate in Belarus plays an important role, as any inversion of it is not without consequences. This article also provides solutions to the problem of climate change

Stokes and anti-Stokes luminescence from cubic elpasolite Cs2NaYF6 crystals doped with Er3+and Yb3+ ions

Er3þ and Yb3þ doped cubic elpasolite Cs2NaYF6 crystals including stoichiometric compositions Cs2NaErF6 and Cs2NaYbF6 have been synthesized under hydrothermal conditions. Absorption, stimulated-emission and gain cross-sections spectra have been determined for the 2F5/2-2F7/2 (Yb3þ) and 4I13/2-4I15/2 (Er3þ) transitions at room-temperature. The maximum σSE values are 1.8 10 21 cm2 at 993 nm (Yb3þ) and 3.8 10 21 cm2 at 1535 nm (Er3þ). Elpasolite crystals provide exceptionally long radiative lifetimes of the excited-states for both ions, namely τ(2F5/2)¼6.3 ms and τ(4I13/2) 32 ms for 10 at% Yb3þ:Cs2NaYF6 and 10 at% Er3þ:Cs2NaYF6 which can be used in high pulse energy Q-switched lasers. Up-conversion luminescence has been studied for Er3þ doped and Er3þ, Yb3þ codoped Cs2NaYF6 crystals