Optical pumping of quantum dot micropillar lasers.

L Andreoli,X Porte,D Brunner,S Reitzenstein,B Moeglen-Paget,L Furfaro,T Heuser,J Große

doi:10.1364/oe.417063

L Andreoli, X Porte + Show 6 more

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https://doi.org/10.1364/oe.417063

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Abstract

Arrays of quantum dot micropillar lasers are an attractive technology platform for various applications in the wider field of nanophotonics. Of particular interest is the potential efficiency enhancement as a consequence of cavity quantum electrodynamics effects, which makes them prime candidates for next generation photonic neurons in neural network hardware. However, particularly for optical pumping, their power-conversion efficiency can be very low. Here we perform an in-depth experimental analysis of quantum dot microlasers and investigate their input-output relationship over a wide range of optical pumping conditions. We find that the current energy efficiency limitation is caused by disadvantageous optical pumping concepts and by a low exciton conversion efficiency. Our results indicate that for non-resonant pumping into the GaAs matrix (wetting layer), 3.4% (0.6%) of the optical pump is converted into lasing-relevant excitons, and of those only 2% (0.75%) provide gain to the lasing transition. Based on our findings, we propose to improve the pumping efficiency by orders of magnitude by increasing the aluminium content of the AlGaAs/GaAs mirror pairs in the upper Bragg reflector.

Highlights

In recent years arrays of vertically emitting lasers have experienced a rebirth based on many novel applications such as 3D sensors for mobile phones1, infrared illumination2, free-space communications3 and high-power lasers for material processing and optical pumping4
We find that αGaAS(λP) has a major influence on the quantum-dot micropillar lasers (QDMLs)’
We have characterized with great detail the inputoutput curves of eight QDMLs from an array with homogenized emission wavelengths

Summary

Introduction

In recent years arrays of vertically emitting lasers have experienced a rebirth based on many novel applications such as 3D sensors for mobile phones, infrared illumination, free-space communications and high-power lasers for material processing and optical pumping. Photonic neural networks have recently received substantial attention8 One of their essential ingredients are energy efficient optical nonlinear elements acting as neurons, as well as creating parallel photonic interconnects. Among the key advantages of vertically emitting semiconductor lasers for neuromorphic computing are multi-GHz signal processing bandwidths, a high photonic neuron density enabled by their small size footprint and in principle low threshold pump powers. Among the key advantages of vertically emitting semiconductor lasers for neuromorphic computing are multi-GHz signal processing bandwidths, a high photonic neuron density enabled by their small size footprint and in principle low threshold pump powers12 The latter is a direct consequence of the high spontaneous emission coupling efficiency β between the lasing mode and quantum dot (QD) gain inside high-quality microcavities

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