We report on cascaded frequency conversion at the single-photon level, consisting of a downconversion from the red (738 nm) to a telecom band (1403 nm) and the reverse upconversion process in the same nonlinear crystal. Detecting the converted single photons suffers from a large noise floor. We were able to recover the signal by implementing a lock-in analyzer technique in the data postprocessing.
© 2012 Optical Society of America
Coherence and Statistical Optics
Original Manuscript: July 18, 2012
Revised Manuscript: September 4, 2012
Manuscript Accepted: September 8, 2012
Published: October 9, 2012
Andreas Lenhard, Sebastian Zaske, and Christoph Becher, "Lock-in detection of single photons after two-step frequency conversion," Opt. Lett. 37, 4254-4256 (2012)