A telecom-wavelength conversion from near-infrared light based on a cold Rubidium atomic ensemble

Exponential photon transmission losses in fiber is a severe limitation to realize long-distance quantum communication. It's helpful to use telecom-wavelength photon transmission to mitigate these absorption losses. However, typical atomic electronic transition from ground-level is in visible wavelengths or near-infrared wavelengths, such as transitions based on Rubidium. Here we report our progress in telecom-wavelength conversion from 780nm to 1475nm and from 795nm to 1530nm in a cold optically thick gas of Rubidium. Both these two conversions are using a diamond configuration transition that we use 5S$_{\mathrm{1/2}}$-5P$_{\mathrm{3/2}}$-4D$_{\mathrm{3/2}}$ cascade transition for the 780nm to 1475nm route and 5S$_{\mathrm{1/2}}$-5P$_{\mathrm{1/2}}$-4D$_{\mathrm{3/2}}$ cascade transition for the 795nm to 1530nm route.