  We have designed and fabricated a shallow-etched grating on gallium arsenide
nanomembranes for efficient chip-to-fiber coupling in quantum photonic
integrated circuits. Experimental results show that the grating provides a
fiber-coupling efficiency of >60 %, a greatly suppressed back reflection of <1
% for the designed wavelength of 930 nm, and a 3-dB bandwidth of >43 nm. Highly
efficient single-photon collection from embedded indium arsenide quantum dots
to an optical fiber was realized with the designed grating, showing an average
sixfold increase in photon count compared to commonly used circular gratings,
offering an efficient interface for on-chip quantum information processing.
