We observed the second order correlation peak for nondegenerate spontaneous parametric down conversion (SPDC) of a pulsed pump at 532 nm into 810 nm and 1550 nm entangled beams. We used a Si avalanche photodiode (APD) to detect the 810 nm photons, and an InGaAs APD to detect those at 1550 nm. We defined both a visibility and signal-to-noise ratio (SNR) based on the data, which were obtained at various pump powers. In contrast to classical imaging systems, for which SNR increases monotonically with transmitted power, the SNR for the correlation peak in our setup exhibited a gradual decay as the pump power increased. We derived an empirical relation for the SNR, which was inversely proportional to the square root of pump power.

Date Published: 26 August 2009
PDF: 11 pages
Proc. SPIE 7465, Quantum Communications and Quantum Imaging VII, 74650J (26 August 2009); doi: 10.1117/12.830776

Published in SPIE Proceedings Vol. 7465:
Quantum Communications and Quantum Imaging VII
Ronald E. Meyers; Yanhua Shih; Keith S. Deacon, Editor(s)