Fourier transform spectroscopies derived from amplitude or phase shaping of broadband laser pulses with applications to adaptive control

Abstract

Laser pulse shapers parameterized with frequency-domain functions lead to simple single-parameter manipulations of spectral amplitude and spectral phase that can encode Fourier-transformable information in molecular signals. The first method introduced modulates the intensity within an excitation spectrum, while the second and third methods manipulate only the spectral phase. Each method operating on an input transform limited laser pulse reveals a second-harmonic spectrum in qualitative agreement with that obtainable with a Michelson interferometer. Operating on an adaptively discovered laser pulse with a complex spectral phase, all three methods reveal a second-harmonic spectrum that captures the essential control mechanism. Finally, a recently developed visualization tool is used to give insight into how these techniques affect an oscillatory and Fourier-transformable second order signal in molecules following non-resonant two-photon absorption.