Researchers at Friedrich-Alexander Universität Erlangen and Max Planck Institute show a path towards very low noise supercontinuum (SC) light sources using chiral light. SC sources provide extremely bright, spatially coherent laser light covering the UV to IR in a rugged, compact format. Their applications to various imaging, sensing, and spectroscopy modalities are countless. Temporal noise/coherence has always been a limiting factor where the SC is generated in fiber through noise-driven processes like soliton fission. In linearly birefringent, all-normal dispersion fibers, SC is generated primarily through coherent nonlinear processes and thus have much improved noise, but these are still limited by nonlinear polarization coupling since SC generation along the fast axis is unstable.

This is not the case with circularly birefringent fibers, here a photonic crystal fiber drawn from a spinning preform. The authors demonstrate that the relative intensity noise (RIN) of the SC output is very weakly dependent on the input pump polarization, and the polarization extinction ratio is better than 17 dB for both RHCP and LHCP outputs across the entire 1.3 octave spectrum. The RIN is limited by the high RIN of the pump laser, but the results promise SC-source based measurements with better temporal resolution, higher sensitivity, and faster acquisition time, improved performance of hyperspectral or multi-photon-type imaging and sensing, and improvements in generating compressed ultrashort pulses.

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