Broadband tunable 100-kHz-rate two-photon laser-induced fluorescence line measurements of CO in high-speed flows

High-speed boundary layers are accompanied by substantial gradients in temperature, pressure, and velocity, which can cause uncertainties in the spectral overlap of intrinsic atomic/molecular and narrowband laser lineshapes. In this work, a broadband KTP optical parametric oscillator is used to minimize the effects of Doppler and/or collisional spectral line broadening, line shifting, and Boltzmann redistribution on two-photon laser-induced fluorescence (TP-LIF) signals. This is demonstrated for 100 kHz line measurements of CO in the highly dynamic conditions within a supersonic jet and Mach 6 boundary layer.