Obtaining the impulse response from nonlinear spectroscopy measurements by laser normalization

In nonlinear spectroscopies, the detected spectrum is determined by the response of the system to the particular excitation pulses, which can vary as excitation energy and pulse duration are tuned. Here, we analytically show that, under reasonable assumptions, the nested integrals that describe the light-matter interaction of the system can be simplified by application of the Fourier convolution and shift theorems, resulting in an expression for the nonlinear spectrum that is a product of the impulsive system response and the interaction laser spectra. The impulsive response can then be obtained by linearly dividing the laser spectrum from the detected signal. We demonstrate our normalization scheme by recovering the impulsive response from two different material systems, highlighting removal of distinct spectral artifacts. (c) 2024 Optica Publishing Group