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Mastering Lateral Radiation Losses in Tunable VCSELs
摘要： This paper deals with the loss mechanisms in tunable vertical-cavity surface-emitting lasers (VCSELs). The strong increase of the threshold gain at the tuning range edges motivates the investigation of the degradation mechanisms presented in this paper. A campaign of simulations performed with our in-house VCSEL ELectroMagnetic (VELM) simulation code, combined with a novel approach based on the study of the Poynting vector, allowed to identify significant lateral radiation losses. The proposal of technology-affordable countermeasures rests on the proper understanding of these phenomena.
关键词： lateral radiation losses,scattering losses,Tunable VCSELs,diffraction
更新于2025-09-23 15:23:52
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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) - Birefringent Surface Gratings for Ultrafast Spin-VCSELs
摘要： The data rates required for optical interconnection in datacenters continue to increase. On the other hand, intensity-modulated vertical-cavity surface-emitting lasers (VCSELs), which are the preferred light source for this task, have a limited bandwidth of at present about 35 GHz [1]. This limit can be overcome with spin-VCSELs that show much faster polarisation and modulation dynamics [2]. In these devices, spin-polarised electrons are injected, by which the degree of circular polarisation of the emitted light can be changed and thus information be encoded. The characteristic eigenfrequency of the laser, corresponding to the resonance frequency in conventional laser diodes, is determined by the birefringence splitting B, namely the frequency difference between the two fundamental polarisation modes of a single-mode VCSEL. Recently a polarisation oscillation frequency of 212 GHz was demonstrated [2]. In that laser the birefringence was induced by bending the sample and employing the elasto-optic effect. Alternatively we have shown that the cavity birefringence can be tuned by mounting VCSELs on piezoelectric substrates or by asymmetric heating, which, however, leads to much lower B. Up to now no truly integrated B-inducing technique existed for a spin-VCSEL that would allow to maintain great similarity to the successful high-efficiency device platform of present oxide-confined VCSELs. In this work, for the first time, we present a VCSEL in which high B of almost 100 GHz stems from a tailored integrated surface grating.
关键词： ultrafast modulation,spin-VCSELs,optical interconnection,surface gratings,birefringence
更新于2025-09-12 10:27:22
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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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Mode Engineering in Linear Coherently Coupled Vertical Cavity Surface Emitting Laser Arrays
摘要： The supermode tuning of coherent 3×1 vertical-cavity surface-emitting laser arrays are characterized and simulated. The array elements are resonantly tuned to achieve coherent operation using selective current injection. Depending on the electrical bias, multiple coherent supermodes are observed above threshold. An effective index model is developed to account for the variable current injection and to simulate the supermodes of the linear array. Agreement between experimental near-field and far-field coherent modes and our model simulations are found both at and above lasing threshold.
关键词： semiconductor laser arrays,Laser modes,phased arrays,vertical cavity surface emitting lasers (VCSELs)
更新于2025-09-11 14:15:04
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Monitoring subwavelength grating structures for vertical-cavity surface-emitting laser applications by spectroscopic ellipsometry
摘要： GaAs based vertical cavity surface emitting lasers (VCSELs) have one of the fastest growing markets due to their numerous applications in imaging technology, optical sensors, and interconnects. Stable, single-mode operation of these laser diodes is often achieved by forming subwavelength structures on the surface of the GaAs semiconductor. Quick and preferably noncontact inspection of the formed nanostructures is desired during the fabrication process. Nanostructure characterization by spectral ellipsometry-based metrologies has become an indispensable tool in the semiconductor industry. An advanced method of ellipsometry is the application of Mueller-matrix ellipsometry, which enables the characterization of structure details difficult to measure or not reachable by using standard ellipsometry measurements. In this paper, the authors present the results of nanostructure characterization by model-based dimension metrology using spectral ellipsometry and Mueller-matrix spectral ellipsometry of substrates during the process of VCSEL fabrication.
关键词： Mueller-matrix ellipsometry,VCSELs,spectroscopic ellipsometry,nanostructure characterization,GaAs
更新于2025-09-11 14:15:04