Advances in quantum dots for single photon sources

Summary form only given. There have been many efforts devoted to realizing the predicted potential of zero-dimensional quantum-confined structures, or quantum dots which were first proposed by Arakawa and Sakaki in 1982. Because of their unique atomic-like discrete states with a delta-function density of states, quantum dots are expected to have many significant properties for photonic and electron device applications. The semiconductor laser with a quantum dot active region promises ultra low and temperature independent threshold current, and high-frequency modulation with negligible chirping effect. Owing to remarkable progress in epitaxial growth of the quantum dots and understanding of device physics, the quantum dot laser has become highly attractive light sources for future metro/access network systems, which led to launch of a new company, QD laser Inc., in Japan. Sources of single photons and entangled photons are needed in the field of quantum information such as quantum cryptography and linear-optical quantum computation. Single photon sources based on InAs quantum dots near 1 mum have been intensively investigated by many researchers. However, there still remain various issues such as too short wavelength for optical fiber long-haul transmission, low temperature operation (<10 K) and low emission efficiency. In this presentation, after briefly reviewing progress in quantum dot technologies for high performance quantum dot lasers and single dot spectroscopy for quantum information technology, we discuss our recent advances in single photon sources including successful demonstration of single photon emission at telecom wavelength (1.3 and 1.55 mum), high temperature (200 K) operation using GaN quantum dots and a highly efficient light emission from quantum dots embedded in a photonic crystal nanocavity.