Multi-Octave Supercontinuum Generation and Frequency Conversion based on Rotational

TL;DR

This paper demonstrates that using longer pulses in molecular gases can enhance nonlinear compression and supercontinuum generation, enabling efficient octave-spanning spectra and pulse compression via rotational alignment effects.

Contribution

It introduces a novel approach of using 80-cycle pulses in molecular gases for supercontinuum generation and pulse compression, leveraging rotational nonlinearity for improved efficiency.

Findings

Achieved over two octaves of spectral bandwidth.

Compressed pulses to 1.7 cycles from longer pulses.

Enabled long-wavelength frequency conversion.

Abstract

The field of attosecond science was first enabled by nonlinear compression of intense laser pulses to a duration below two optical cycles. Twenty years later, creating such short pulses still requires state-of-the-art few-cycle laser amplifiers to most efficiently exploit 'instantaneous' optical nonlinearities in noble gases for spectral broadening and parametric frequency conversion. Here, we show that nonlinear compression can in fact be much more efficient when driven in molecular gases by pulses substantially longer than a few cycles, due to enhanced optical nonlinearity associated with rotational alignment. We use 80-cycle pulses from an industrial-grade laser amplifier to simultaneously drive molecular alignment and supercontinuum generation in a gas-filled capillary, producing more than two octaves of coherent bandwidth and achieving >45-fold compression to a duration of 1.7 cycles. As the enhanced nonlinearity is linked to rotational motion, the dynamics can be exploited for long-wavelength frequency conversion and compressing picosecond lasers.