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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Brightness Enhancement in Non-Hermitian VCSELs
摘要： Vertical Cavity Surface Emitting lasers (VCSELs) are compact and efficient light sources useful for a variety of applications. However, due to lack of a transverse mode control mechanism, such lasers suffer from poor spatial beam quality, intrinsic spatiotemporal instabilities and nonlinear destabilizing effects such as filamentation and spatial hole burning [1]. Therefore, there is a need for new strategies to manipulate the light wave dynamics to enhance the stability of VCSELs. Recently, non-Hermitian media have become a flexible platform for new functionalities such as asymmetric coupling, unidirectional invisibility, single mode lasing [2-3]. In this presentation, we propose a novel stabilization mechanism for VCSLEs to obtain bright and narrow beams. The mechanism relies on non-Hermitian configuration of the laser potential, achieved by simultaneous spatial modulation of the refractive index and gain-loss profiles. In particular, we consider axisymmetric non-Hermitian potentials expressed as: n(r)=nR cos(qr)-inI cos(qr-?) where nR and nI are the amplitude of the refractive index and gain-loss modulations, and ? is the relative phase shift between them. Such potentials may confine the emitted light around the central part of VCSELs, through unidirectional-inward radial coupling among the transverse modes [4]. The interplay of the relative strength and relative phase of the index and gain-loss modulations manipulate the wave dynamics of such lasers to emit powerful and narrow beams of high brightness. We use the mean-field paraxial model to study the spatiotemporal dynamics of such VCSELs with non-Hermitian potentials. The output emission of conventional VCSEL and modified VCSEL with concentric non-Hermitian configuration is shown in Fig. 1(a,b), illustrating irregular and stable localized pattern, respectively. We assess the performance through the central intensity enhancement [see Fig. 1(c)] and field concertation [see Fig. 1(d)]. The spatial dynamics for a representative point is provided in Fig. 1(e). The stationary intensity profile and its corresponding cross-section show that intensity is strongly concentrated at r=0 due to the favoured radial coupling of inward propagating waves, as depicted in the transverse field flow on the inset [see Fig. 1(e)].
关键词： VCSELs,refractive index,non-Hermitian media,gain-loss profiles,spatial modulation,brightness enhancement
更新于2025-09-11 14:15:04
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[Springer Tracts in Modern Physics] Parity-time Symmetry and Its Applications Volume 280 || Constant-Intensity Waves in Non-Hermitian Media
摘要： When waves propagate through a non-uniform potential landscape their interference typically gives rise to a complex intensity pattern. In this chapter we review our work on how to entirely suppress these intensity variations by adding system-specific gain and loss components to the potential. The resulting constant-intensity (CI) waves are entirely free of interference fringes and get perfectly transmitted across any such non-Hermitian scattering landscape that is put in their way. We discuss how to generalize this concept to more than one dimension and to the non-linear regime where these special wave states open up the way to study the phenomenon of modulation instability in non-uniform potentials. Experimental implementations of these unique wave states are envisioned not just in optics, but also in other fields of wave physics such as in acoustics.
关键词： Acoustics,Modulation instability,Optics,Constant-intensity waves,Wave propagation,Non-Hermitian media
更新于2025-09-10 09:29:36