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Register a new userStorage of up-converted telecom photons in a doped crystal
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We report on an experiment that demonstrates the frequency up-conversion of telecommunication wavelength single-photon-level pulses to be resonant with a $mathrm{Pr}^{3+}$:$mathrm{Y}_2mathrm{Si}mathrm{O}_5$ crystal. We convert the telecom photons at $1570,mathrm{nm}$ to $606,mathrm{nm}$ using a periodically-poled potassium titanyl phosphate nonlinear waveguide. The maximum device efficiency (which includes all optical loss) is inferred to be $eta_{mathrm{dev}}^{mathrm{max}} = 22 pm 1,%$ (internal efficiency $eta_{mathrm{int}} = 75pm8,%$) with a signal to noise ratio exceeding 1 for single-photon-level pulses with durations of up to 560$,$ns. The converted light is then stored in the crystal using the atomic frequency comb scheme with storage and retrieval efficiencies exceeding $eta_{mathrm{AFC}} = 20,%$ for predetermined storage times of up to $5,mumathrm{s}$. The retrieved light is time delayed from the noisy conversion process allowing us to measure a signal to noise ratio exceeding 100 with telecom single-photon-level inputs. These results represent the first demonstration of single-photon-level optical storage interfaced with frequency up-conversion.
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Up to this point streak-cameras have been a powerful tool for temporal characterization of ultrafast light pulses even at the single photon level. However, the low signal-to-noise ratio in the infrared range prevents measurement on weak light sources in the telecom regime. We present an approach to circumvent this problem. The method utilizes an up-conversion process in periodically poled waveguides in Lithium Niobate. We convert single photons from a parametric down-conversion source in order to reach the point of maximum detection efficiency of commercially available streak-cameras. We explore phase-matching configurations to investigate the up-conversion scheme in real-world applications.
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