  We report a large area photo-diode based homodyne detector for free-space
quantum coherent communication. The detector's performance is studied in terms
of detection bandwidth and electronic noise for shot-noise limited quantum
signal detection. Using large area photo-diodes increases signal collection
efficiency from turbulent atmospheric channels, in comparison with typical
fibre based free-space homodyne detectors. Under identical atmospheric
turbulence and receiver aperture conditions, our homodyne detector based on 1mm
diameter photo-diode experiences 0dB loss due to turbulence while a 10um fibre
based detector experiences 13.5dB of signal loss over a 700km free-space link,
at 90 degree elevation angle.
