High Harmonic Generation from Isolated Bound States: Tunable Emission Spectra and Mollow Triplets

Abstract: High harmonic generation (HHG) is a highly nonlinear emission process in which systems driven by intense laser pulses emit integer multiples (harmonics) of the driving field. This feature is considered universal to all occurrences of HHG. Here we show that a strong nonlinear response of certain systems can split the HHG spectrum into non-harmonic Mollow-type triplets, imprinting the internal electronic characteristics and confining potential on the HHG spectrum. The spectral lines become tunable by the driver field. These phenomena are universal to any material system with isolated bound states. We identify the conditions under which our predictions become accessible and propose experimental systems to observe them.