Stuttgart 2012 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 66: Photonik 4

Q 66.5: Vortrag

Freitag, 16. März 2012, 15:00–15:15, V38.01

Frequency Down-Conversion at the Single Photon Level — •Andreas Lenhard, Sebastian Zaske, and Christoph Becher — Universität des Saarlandes, FR 7.2 Experimentalphysik, Campus E2.6, 66123 Saarbrücken

Long-range quantum communication over existing fiber networks needs photons at low-loss telecommunication wavelengths, serving as qubits. Photons of a quantum emitter in the red or near-infrared can be transfered to the telecom bands via frequency downconversion using a strong mixing wave. This conversion in general suffers from noise generated by Raman scattering [1] or optical parametric fluorescence. Using a mixing field with a wavelength much longer than the target wavelength drastically reduces this noise background.

We report on the frequency down-conversion of weak coherent pulses from 710 nm to the telecom O-band at 1310 nm using difference frequency generation. The pulses have a width of 10 ns, a repetition rate of 500 kHz and contain 1 photon on average. The strong pump field at 1550 nm is generated by a cw optical parametric oscillator. As nonlinear medium we use 4 cm long PPLN ridge waveguides. The converted pulses are detected by InGaAs/InP APDs. We achieve an internal conversion efficiency of 68 % and a signal-to-noise ratio of 114. Due to losses of narrow-band spectral filtering the over-all detection efficiency is currently limited to 2 %. These results pave the way to highly efficient, nearly noise-free frequency translation of single emitters like quantum dots or color centers in diamond to the telecom bands.
Zaske et al., Optics Exp. 19 12825 (2011)