Jamil - Supplemental information - 3rd revision

Supplemental material: “On-chip generation and guiding of
quantum light from a site-controlled quantum dot”.
Schwagmann,1,2 Martin B. Ward,2 Yarden Brody,1,2 David J. P. Ellis,2 Ian Farrer,1
Jonathan P. Griffiths,1 Geb A. C. Jones,1 David A. Ritchie,1 and Andrew J. Shields2*
Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge
CB3 0HE, United Kingdom.
Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science
Park, Milton Road, Cambridge, CB4 0GZ, United Kingdom
Experimental set-up
A schematic of the experimental set-up is shown in Fig. S1. The sample is
placed on the cold finger in a continuous flow helium cryostat. The top lid of the
cryostat is modified to support collection from the side of the sample, at 90 degrees
with respect to the excitation from the top. The in-plane emission is collected with a
50X microscope objective, dispersed by a spectrometer and detected by a chargecoupled device camera. For the auto-correlation measurements, light dispersed by the
spectrometer is split by a 50:50 beamsplitter and detected by two silicon avalanche
photon detectors (APDs). Photon coincidences are recorded by a computer using a
time-correlated single-photon counting module.
Figure S1. Schematic illustration of the experimental set-up. Dimensions are not to scale.
Alignment precision
We determine the precision of our alignment method by a statistical analysis
of several photonic crystal devices. Using a wafer with etched pits in an array
configuration identical to the one used for the overgrown sample, we fabricated
photonic crystal cavities under the same conditions. This time, the slab containing the
quantum dot layer was not overgrown allowing us direct access to the pit location
using conventional imaging techniques.
Large arrays of L3 cavities with the pits in the center of the cavity were
fabricated. An SEM image of such a device is shown in Fig. S2. The symmetry of L3
cavities helps in the estimation of the lateral position of the center and they were used
instead of waveguide structures. In Fig. S2, the etched pit appears as a dark spot in the
middle of the cavity. We measured over 60 devices from which we estimated an
average offset of the pit with respect to the cavity center of 64 nm with a standard
deviation of 21 nm. No strong bias was found along any particular direction. We note
that the alignment marks are covered during the overgrowth procedure, leaving them
exposed for optimal alignment in the subsequent electron beam lithography step for
the fabrication of the photonic crystal structure.
Figure S2. Scanning electron microscope image of an L3 cavity. The dark spot in the middle is the
etched pit.