3.4 μm to 660 nm wavelength conversion using Er3+ doped materials

The 2-15 mu m spectral range hosts many optical sensing applications from biology to environmental monitoring, and infrared spectroscopy is a simple and reliable way to provide fast and in-situ analysis method. Rare-earth ion emissions within chalcogenide glasses with low phonon energies proved to be efficient to address mid-IR luminescence based sensing applications. In particular, they give promising results for the development of all-optical gas sensors in the 3 to 5 mu m spectral range based on IR conversion into visible light using rare earth excited state absorption mechanisms. In this article, we report the wavelength conversion of 3.4 mu m radiation into 660 nm in Er3+: KPb2Cl5 bulk crystal, Er3+: Ga5Ge20Sb10S65 and Er3+: Ga5Ge20Sb5S70 glasses using an excited state absorption process. This wavelength conversion is the result of the excitation of Er3+ ions following the excited state absorption of IR photons and the Er3+ ions subsequent spontaneous emission in the visible domain. Using an 808 nm pumping, a 3.4 mu m photon excited state absorption gives rise to a 660 nm emission. This wavelength conversion device can be further implemented for methane all-optical sensing at 3.4 mu m, for the development of remote all-optical methane mid-IR sensors with only visible and near-IR input and output signals. This all-optical concept enables the use of silica fibers over large distances, thus considerably increasing the scope of possible applications.