Special Issue on Nanostructures in Photonics
More than six decades passed, since the first patent and publications on the importance of quantum wells (QWs), two-dimensional nano-heterostructures, for reducing the threshold current density and thus increasing the efficiency and output power of semiconductor lasers by Dingle and Henry. Breakthroughs of heterostructure growth based on the development of MBE (molecular beam epitaxy) and MOCVD (metal-organic chemical vapor deposition) presented the basis of this progress. Today one can praise QW-lasers as the first “green” lasers. Close to 100% of all semiconductor lasers using all kinds of material systems are now based on quantum wells. Theoretical work predicted that, reducing further the dimensionality of the gain material to 1D and 0D structures, should additionally lead to huge advantages of performance of lasers. Smaller threshold current densities, larger material gain, larger modulation frequency, increased temperature stability were dreamed of. Attempts to extend the quantum well success story to quantum wires and “technology based” quantum dots, where quantum well laser structures were etched to create nano-size pillars, failed to produce superior devices operating again at room temperature like QW-lasers.
The discovery of self-organized growth in strained hetero-structures (Stranski-Krastanov, submonolayer deposition,..) in the 1990s, to create large densities of quantum dots, showing actually more than the predicted huge material gain, lead to an explosion of research on nanostructures and their applications for a large diversity of devices all around the world. As of today, Google Scholar counts ~ 3 million of publications on this subject. QD-lasers show today the lowest threshold current density of 6 A/cm2 per QD-layer, the best temperature stability,… of all semiconductor lasers. Passively mode-locked lasers generate hat-like frequency combs enabling bit rates in the 4-5 Tb/s range. Quantum dots conquered in the last years territory not thought about 30 years ago, like becoming simple to fabricate sources for q-bit and entangled photon emitters, probably soon operating at room temperature, for novel memories combining the best of flash and DRAM, hailed as the “holy grail of memories”.
This volume provides the readers with a glimpse to a variety of most recent and important achievements on some of the most important areas of research on such nanostructures.
