99% beta factor and directional coupling of quantum dots to fast light in photonic crystal waveguides determined by spectral imaging

Abstract

Semiconductor quantum dots in photonic crystal waveguides are building blocks for quantum technology. Placing the dots at locations where the waveguide modes have circular polarization enables light emission in only one direction with a high probability of coupling to the mode, the beta factor. The authors use spectral imaging to determine the beta factor and the directionality, doing away with assumptions on emission rates into nonguided modes. In the fast-light regime, they find coupling, close to unity, and determine the quantum-dot position inside the waveguide.