Broadband Purcell factor enhancements in photonic-crystal ridge waveguides

We introduce the concept and theory for a photonic-crystal ridge waveguide in high index semiconductors that can be used to tailor the single-photon emission of an embedded quantum dot. The design exploits a band structure with a large bandwidth of slow light. By tuning the device geometry, the group velocity of the fundamental waveguide mode and the Purcell factor (enhanced spontaneous emission) can be uniquely controlled. We give reference designs with a Purcell factor of at least 10 and 43 with a large bandwidth of 435 and 51 GHz (similar to 1.8 meV and 0.21 meV), respectively. Applications toward chip-based single-photon emitters are discussed, and a comparison with dispersion-engineered planar photonic-crystal waveguides is also given.