  We demonstrate an important step towards on chip integration of single photon
sources operating at room temperature fiber coupling of a directional quantum
emitter with back-excitation. Directionality is achieved with a hybrid
metal-dielectric bullseye antenna, while back-excitation is permitted by
placement of the emitter at or in a sub-wavelength hole positioned at the
bullseye center. Overall, the unique design enables a direct laser excitation
from the back of the on-chip device and very efficient coupling of the highly
collimated photon emission to either low numerical aperture (NA) free space
optics or directly to an optical fiber from the front. To show the versatility
of the concept, we fabricate devices containing either a colloidal quantum dot
or a silicon-vacancy center containing nanodiamond, which are accurately
coupled to the nano-antenna using two different nano-positioning methods. Both
back-excited devices display front collection efficiencies of about 70 % at NAs
as low as 0.5. Moreover, the combination of back-excitation with forward low-NA
directionality enables direct coupling of the emitted photons into a proximal
optical fiber without the need of any coupling optics, thereby facilitating and
greatly simplifying future integration.
