1 kHz single-shot multi-focus fs/ps-CARS for spectroscopy and thermometry in reacting flows

We present a simple and cost-effective method allowing for the performance of fs/ps-CARS spectroscopy and thermometry on multiple points distributed in lines and arrays in single shot and at a high repetition rate (1 kHz). The method is based on light polarization separation using successive birefringence crystal stacks and enables non-uniform spatial sampling of multiple foci. We show that our approach preserves identical pump/Stokes excitation profiles across the multiple measurement volumes. We achieved simultaneous single-shot CARS measurements at up to eight points in room-temperature flows, and at two points in a CH 4 /air flame, resolving steep temperature gradients (∼2000K over 1 mm) and capturing highly correlated temporal dynamics across multiple acquisition channels.