  Photonic integrated circuits that are manufactured with mature semiconductor
technology hold great promise for realizing scalable quantum technology.
Efficient interfaces between quantum emitters and nanophotonic devices are
crucial building blocks for such implementations on silicon chips. These
interfaces can be realized as nanobeam optical cavities with high quality
factors and wavelength-scale mode volumes, thus providing enhanced coupling
between nanoscale quantum emitters and nanophotonic circuits. Realizing such
resonant structures is particularly challenging for the visible wavelength
range, where many of the currently considered quantum emitters operate, and if
compatibility with modern semiconductor nanofabrication processes is desired.
Here we show that photonic crystal nanobeam cavities for the visible spectrum
can be designed and fabricated directly on-substrate with high quality factors
and small mode volumes. We compare designs based on deterministic and
mode-matching methods and find the latter advantageous for on-substrate
realizations. Our results pave the way for integrating quantum emitters with
nanophotonic circuits for applications in quantum technology.
