Novel lasers from quantum nanostructures
A quantum dot is a semiconductor nanocrystal that confines its excitons in all three spatial dimensions. Excitons are solid quasiparticles consisting of an electron and a hole and their confinement gives rise to a wealth of physical phenomena. Growth of InAs (Indium Arsenide) on the dielectric InP (Indium Phosphide) under controlled conditions results in the formation of a series of quantum dots that now form what is called a quantum wire. The NANOMAT project has studied this self-assembled formation of nanomatre-sized droplets of semiconductor material on a lattice-mismatched substrate (like InAs/InP). This opens up the possibility of a new technology in which the band structure can be engineered on the nanoscale in all three dimensions. Specifically, photoluminescence, i.e. absorption and consequently radiation of light, of an InAs/InP quantum wire has been studied experimentally and lasing close to the critical wavelength of 1.55μm for telecommunications has been achieved. Namely, lasing at 1.45µm at 100K from a single layer quantum wire device has been obtained, and lasing up to 250K from a three layer quantum wire device with low threshold current. A 1.55µm laser with nanostructures as the active material will have a variety of applications in the telecoms’ industry. Project partners seek further research and development support since their current results show that such a laser is feasible. The laser will most likely work at high temperatures, dispensing with thermoelectric coolers therefore resulting in a substantial cost saving. Moreover, non-zero dispersion that now seems to be a potential barrier will be addressed with the stacking of quantum wires. The developed high-performance laser with low threshold currents and high thermal stability seems to have a very promising medium and long term potential for exploitation in optical data storage and nanoelectronics and is only nano-steps away from the critical 1.55μm wavelength.
