Perspectives on Advances in Quantum Dot Lasers and Integration with Si Photonic Integrated Circuits

Abstract

Epitaxially grown quantum dot (QD) lasers are emerging as an economical approach to obtain on-chip light sources. Thanks to the three-dimensional confinement of carriers, QDs show greatly improved tolerance to defects and promise other advantages such as low transparency current density, high temperature operation, isolator-free operation, and enhanced four-wave-mixing. These material properties distinguish them from traditional III–V/Si quantum wells (QWs) and have spawned intense interest to explore a full set of photonic integration using epitaxial growth technology. We present here a summary of the most recent developments of QD lasers grown on a CMOS-compatible (001) Si substrate, with a focus on breakthroughs in long lifetime at elevated temperatures. Threading dislocations are significantly reduced to the level of 1 × 106 cm–2 via a novel asymmetric step-graded filter. Misfit dislocations are efficiently blocked from the QD region through well-engineered trapping layers. A record-breaking extrapolated lifetime of more than 200000 hours has been achieved at 80 °C, forecasting that device reliability is now entering the realm of commercial relevance and a monolithically integrated light source is finally on the horizon.

Electronic and Optical Properties of InAs QDs Grown by MBE on InGaAs Metamorphic Buffer

“…Changes in the strain conditions during the growth of QDs from sample to sample while increasing the In content in the buffer layer underneath may lead to inducing an in-plane asymmetry of QDs’ shape or strain anisotropy, both affecting the mixing of valence band states (where the light and heavy-hole states mixing is of crucial importance), leading to a non-zero DOLP of QD emission [ 59 ]. The possible QD shape asymmetry is characteristic for the QDs’ growth under lower strain, and hence the stronger influence of the atomic steps on growth anisotropy (along the crystallographic directions [110] and [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]) may occur, as it was already observed for other types of dots grown by MBE in conditions of smaller difference in the lattice constants between the substrate/buffer and the QD materials [ 54 , 55 ]. It is difficult to resolve which of the parameters (QD shape asymmetry or strain anisotropy) is the main factor responsible for the observed DOLP change, especially for inhomogeneous systems where the differences in dot-to-dot shape and strain variations can be significant and only average properties can be specified for an ensemble of QDs [ 59 , 60 , 61 ], but one can expect that both do contribute.…”

“…Semiconductor self-assembled epitaxial quantum dots (QDs) have been demonstrated to be suitable candidates for use in a wide range of optoelectronic devices, from lasers [ 1 , 2 ], optical amplifiers [ 1 , 3 ], or other broadband sources [ 4 , 5 ] to quantum computing and quantum information processing employing QD-based non-classical emitters [ 6 , 7 , 8 , 9 , 10 ]. In particular, the possibility of controlling the parameters of QDs via the materials choice, and the related band structure and strain engineering, makes them attractive for applications due to the possibility of obtaining compatibility with the existing silica-based optical fiber infrastructure and emission in the high-transmission spectral range of telecommunication windows, characterized by the lowest attenuation in the third telecom or minimum optical signal dispersion in the second telecom windows [ 10 , 11 ].…”

Time-delayed reservoir computing based on a dual-waveband quantum-dot spin polarized vertical cavity surface-emitting laser

“…Following this lead, quantum dot (QD) based devices exhibit unique features, compared to QWs that are highly sought in neuromorphic schemes. Enhanced temperature insensitivity, originating from the three-dimensional confinement of carriers in the nanostructure, can alleviate the need for power-hungry active cooling schemes in QD based neuromorphic schemes [17]. Furthermore, recent works, have demonstrated that active QD layers can be grown directly over silicon, providing high-quality lasers [17], thus avoiding complex hybrid integration processes [18].…”

Hybrid Mie-Tamm photonic structure as a highly directional GHz single-photon source

“…These QDs show excellent purity [24] and indistinguisability [25]. Moreover, as these quantum emitters are based on III-V semiconductors, they can be integrated in photonic integrated circuits [26][27][28] and even in silicon substrates [29]. With these materials choice, we present in the following the optimum design parameters to extract from the sample 3.6 GHz single-photon rates in a narrow cone of NA = 0.17.…”