Non-Collinear Optical Parametric Oscillator for Video Rate Stimulated Raman Spectroscopy of Microplastics

Microplastics are widely spread in our global environment. We find them not only in our oceans and inland waters all over the world but also increasingly in our drinking water [1]. This is even more alarming by the fact that toxins or contaminations often accumulate those particles and their impact of the environment is widely uninvestigated. Femtosecond Optical Parametric Oscillators are very suitable for microscopy and spectroscopy experiments due to their broadband tuning range at high output power [2,3]. Because of the unique ultrabroadband phasematching conditions in BBO-crystals, OPOs in non-collinear geometry [4] allow for very fast tuning speeds and values of more than 100 nm/ms have been demonstrated [5]. Here, we present a Non-collinear Optical Parametric Oscillator (NOPO) with a fast tunable output spectrum between 650 and 950 nm, which we use to demonstrate Stimulated Raman Scattering of microplastics in a water flow in video rates.