Spectral tuning of a broadband optical pulse via stimulated Raman scattering of a prealigned molecule

Abstract

The nonlinear spectral broadening of a near-infrared laser pulse propagating through pre-aligned molecules is investigated experimentally in a pump-probe scheme. The spectral shift of over 100 nm as well as spectral shaping is achieved via tuning the experimental conditions such as pump-probe delay, gas pressure, and pulse energy. Numerical simulation based on the nonlinear Schr\"odinger equation shows that the experimentally observed spectral tuning is due to the competition between different nonlinear effects, i.e., stimulated Raman scattering, the Kerr effect, and molecular alignment. Adjusting the pump-probe delay properly can decouple different nonlinear processes and allows for spectral tuning in a controlled way. This scheme is demonstrated to be attractive for the generation of few-cycle laser pulses with a frequency-tunable spectrum, broadband pulse shaping, and many strong field applications in the visible range.