Abstract
We report and analyze the supermode switching with current injection found for coherently-coupled dual-element vertical cavity surface emitting laser arrays. The output power, spectral characteristics, and far-field mode profile are measured for a range of bias current operating conditions. The coupling-induced enhanced output power from an in-phase or out-of-phase supermode is confirmed when approximately equal currents are injected into each array element. We observe that the coherent supermode switches from out-of-phase to in-phase supermode with increasing equal current injection. The switching is found to be consistent with coupled mode theory and a 1-dimensional spatial supermode model. The calculated modal gain of the out-of-phase and in-phase array supermodes are consistent with the observed switching of the coherent supermodes.
Highlights
C OHERENTLY-coupled phased laser diode arrays have been previously explored for generation of diffraction limited and/or high brightness beams [1]
A pair of vertical cavity surface emitting laser (VCSEL) can operate in a single coherent supermode which extends into both cavities and can be classified as the out-of-phase or in-phase array supermode, respectively [7]
We report and analyze the supermode switching observed for dual-element coherentlycoupled photonic crystal VCSEL arrays [8] with approximately equal current injection
Summary
C OHERENTLY-coupled phased laser diode arrays have been previously explored for generation of diffraction limited and/or high brightness beams [1]. We report and analyze the supermode switching observed for dual-element coherentlycoupled photonic crystal VCSEL arrays [8] with approximately equal current injection. D. Choquette are with the Department of Electrical and Computer Engineering, University of Illinois, dominant lasing supermode should switch with increasing current injection. We observe the lowest threshold lasing supermode to switch from out-of-phase to in-phase with increasing current injection, consistent with the index change accompanying the increasing bias current. By independently adjusting the bias currents injected into the two adjacent cavities, the elements can be tuned into resonance where the array operates in a coherent supermode [11]. For identical VCSEL elements, coherent supermode emission is expected with approximately equal currents in each cavity.
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