We demonstrated a large-scale space-time-multiplexed homodyne optical neural network (ONN) using arrays of high-speed (GHz) vertical-cavity surface-emitting lasers (VCSELs). Injection locking enables precise phase control over tens of VCSEL devices simultaneously, facilitating photoelectric-multiplication-based matrix operations and all-optical nonlinearity, operating at the quantum-noise limit. Our VCSEL transmitters exhibit ultra-high electro-optic conversion efficiency (Vπ=4 mV), allowing neural encoding at 5 attojoule/symbol. Three-dimensional neural connectivity allows parallel computing. The full-system energy efficiency reaches 7 fJ/operation, which is >100-fold better than the state-of-the-art digital microprocessors and other ONN demonstrations. Digit classification is achieved with an accuracy of 98% of the group truth.
Spin-controlled lasers are highly interesting photonic devices and have been shown to provide ultra-fast polarization dynamics in excess of 200 GHz. Another class of modern semiconductor lasers are high-beta emitters which benefit from enhanced light-matter interaction due to strong mode confinement in low-mode-volume microcavities. We combine the advantages of both laser types to demonstrate spin-lasing in high-beta microlasers for the first time. For this purpose, we realize bimodal high-beta quantum dot micropillar lasers for which the mode splitting and the polarization-oscillation frequency can be engineered via the pillar cross-section. The microlasers show very pronounced spin-lasing effects with polarization oscillation frequencies up to 15 GHz.
Spin-controlled lasers are highly interesting photonic devices and have been shown to provide ultra-fast polarization dynamics in excess of 200 GHz. Another class of modern semiconductor lasers are high-beta emitters which benefit from enhanced light-matter interaction due to strong mode confinement in low-mode-volume microcavities. We combine the advantages of both laser types to demonstrate spin-lasing in high-beta microlasers for the first time. For this purpose, we realize bimodal high-beta quantum dot micropillar lasers for which the mode splitting and the polarization-oszillation frequency can be engineered via the pillar cross-section. The microlasers show very pronounced spin-lasing effects with polarization oscillation frequencies up to 16 GHz.
We present an alignment procedure which allows for precise gluing of a structure with an optically pumped quantum emitter to the end face of zirconia ferrule with a specially fabricated high numerical aperture single-mode fiber. The proposed method is an important step towards building a single-photon source based on an InGaAs quantum dot emitting in 1.3 μm range and located deterministically in a microlens fabricated by in-situ electron beam lithography and plasma etching to improve the photon extraction efficiency. Since single QDs are very dim at room temperature which hinders QD-fiber adjustment by maximizing the collected photoluminescence signal, the developed method uses light back-reflected from the top surface of the sample with microlens as a feedback signal. Using this approach, we were able to position the high-NA fiber over the center of the microlens with an accuracy of about 150 nm in a lateral direction and 50 nm in a vertical direction. The alignment accuracy was confirmed by following the room temperature emission from quantum wells embedded in a reference microlens. We also present initial low temperature tests of the coupling system mounted in a compact and portable Stirling cryocooler.
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