Abstract
We explore the dynamics and directionality of spontaneous emission from self-assembled In(Ga)As quantum dots into transverse-electric–polarized guided modes in GaAs two-dimensional photonic-crystal waveguides. The local group velocity of the guided waveguide mode is probed, with values as low as measured close to the slow-light band edge. By performing complementary continuous-wave and time-resolved measurements with detection along and perpendicular to the waveguide axis, we probe the fraction of emission into the waveguide mode ( factor). For dots randomly positioned within the unit cell of the photonic-crystal waveguide, our results show that the emission rate varies from close to the slow-light band edge to within the two-dimensional photonic band gap. We measure an average Purcell factor of for dots randomly distributed within the waveguide and maximum values of close to the slow-light band edge. Spatially resolved measurements performed by exciting dots at a well-controlled distance of 0–45 from the waveguide facet highlight the impact of disorder on the slow-light dispersion. Although disorder broadens the spectral width of the slow-light region of the waveguide dispersion from to , we find that emission is nevertheless primarily directed into propagating waveguide modes. The ability to control the rate and directionality of emission from isolated quantum emitters by placing them in a tailored photonic environment provides much promise for the use of slow-light phenomena to realize efficient single-photon sources for quantum optics in a highly integrated setting.
- Received 24 July 2014
- Revised 3 September 2014
DOI:https://doi.org/10.1103/PhysRevB.90.115310
©2014 American Physical Society