We show that coherent supermode emission is observable in hexagonal ring shaped 6 and 12 element photonic crystal VCSEL arrays under relatively short (~100ns) pulse operation with all array elements connected in parallel.
We report on the mode evolution of coupled dual-element laser arrays biased in the coherently coupled region, exploring both theoretical and experimental aspects. Utilizing a complex waveguide simulation, we identify two supermodes operating within the coherently coupled region. The formation of the supermodes leads to enhanced output power, visibility, and a photon-photon resonance frequency surpassing the carrier-photon resonance frequency. Such favorable attributes are facilitated by the formation of anti-guided cavities through current injection. Finally, we conduct a comparative analysis of mode characteristics under strong and weakly anti-guiding conditions to identify the impact on the supermode characteristics.
We show that a photonic crystal triangular VCSEL array can lase in three possible coherent supermodes with three distinctive far-field beam profiles. To determine a dominant supermode at a given level of current injection, we define the peak ratio as the ratio between any sidelobe peak to the central peak of the Fourier transform of the far-field. The peak ratio and the number of sidelobes we show provides a numerical method to determine the dominant supermode in a coherent triangular VCSEL array. Coherent operation is found with approximately equal current injection into each element producing a single spectral resonance and structured far-field profile. We compare experimentally extracted peak ratios for an array nominally emitting at 850nm to those calculated from a complex waveguide modal simulation. This Fourier method based far-field analysis may be useful to determine a useful beam profile for target applications.
We study the supermode dynamics of optically coupled but electrically isolated dual-element photonic crystal vertical cavity surface emitting laser (VCSEL) arrays. The optical coupling is characterized by experimentally extracting a complex coupling coefficient, where the real component is related to the frequency splitting between the two array nonHermitian supermodes, whereas the imaginary coupling coefficient represents the gain difference between these two supermodes. The imaginary coefficient is derived from the coupling-induced excess output power. We compare three photonic crystal periods and find the largest value arising from the closest separation between two cavities. For the array with the highest imaginary component, the real part is determined which is related to the photon-photon modulation resonance, which has the potential to increase the VCSE digital modulation rate.
Coherent optical coupling in VCSEL arrays introduces novel and desirable behaviors that can manifest themselves in many ways. We explore some of these behaviors using common characterization techniques but using large datasets, and show how we use computational data analysis methods to analyze datasets in an automated and scalable manner.
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