  A highly pure and stable single-photon source is prepared that comprises a
well-designed pillar array in which each pillar contains only a few InAs
quantum dots. A nano-pillar in this array is in direct contact with a fiber end
surface and cooled in a liquid-He bath. Auto-correlation measurement shows that
this source provides an average $g^{(2)}(0)$ value of 0.0174 in the measured
excitation-power range. This photon source and fiber coupling are quite rigid
against external disturbances such as cooling-heating cycles and vibration,
with long-term stability.
