Broadband luminescence upconversion spectroscopy
The possibility to generate the sum-frequency between the luminescence of a sample and an ultrashort pulse below the ns-range offers a solution to measure dynamics and kinetics which are faster than the electronic limit. Especially, the build up process of the luminescence can be studied. For that purpose, we use a non-collinear geometry with an ultrashort sub 35 fs pulse (gate-pulse) to generate the sum-frequency in a nonlinear optical crystal. The setup allows a single shot broadband upconversion in the visible spectrum with a fixed geometry by using a thin BBO of a few microns. The upconversion only takes place at the temporal superposition of luminescence and gate-pulse. By delaying pump or gate-pulse, it is possible to scan over the luminescence signal with a temporal resolution in the order of the pulse duration. The whole spectrum of upconverted light is collected in a spectrometer with an UV-enhanced camera. The advantage of this setup in comparison to a streak camera is a high temporal resolution (<100 fs) and an opportunity to measure dynamics in the infrared spectrum by using a nonlinear optical crystal which is optimized for this purpose.