Optimization of stimulated rotational Raman scattering over vibrational scattering in a hydrogen-filled fiber

We present the first, to the best of our knowledge, investigation of the gain competition between rotational and vibrational stimulated Raman scattering (SRS) in the transient regime for a hydrogen (H )-filled antiresonant fiber (ARF) with the aim of generating multispectral emission composed of only rotational SRS. We show numerically and experimentally that purely rotational emission requires optimization of ARF length and spectral transmission, pump power and polarization, and H pressure. In this work, the H -filled ARF is pumped by 40 kW, 7 ns pulses at λ = 1.06 µm to produce six discrete rotational lines from 1.1 to 1.7 µm with unique temporal profiles and pulse energies up to tens of microjoules.