Gravity-like potential traps light and stretches supercontinuum in photonic crystal fibers

TL;DR

This paper introduces a novel physical mechanism, a gravity-like potential, that explains the generation of blue and violet light in supercontinuum spectra from infrared femtosecond pulses in photonic crystal fibers, expanding understanding of supercontinuum shaping.

Contribution

It proposes that radiation trapping in a gravity-like potential created by accelerating solitons significantly influences the short-wavelength edge of supercontinuum spectra, a previously unexplained phenomenon.

Findings

Gravity-like potential traps short-wavelength light

Accelerating solitons create a potential affecting supercontinuum

This mechanism explains blue and violet light generation

Abstract

The use of photonic crystal fibers pumped by femtosecond pulses has enabled the generation of broad optical supercontinua with nano-joule input energies. This striking discovery has applications ranging from spectroscopy and metrology to telecommunication and medicine. Amongst the physical principles underlying supercontinuum generation are soliton fission, a variety of four-wave mixing processes, Raman induced soliton self-frequency shift, and dispersive wave generation mediated by solitons. Although all of the above effects contribute to supercontinuum generation none of them can explain the generation of blue and violet light from infrared femtosecond pump pulses, which has been seen already in the first observations of the supercontinuum in photonic crystal fibers. In this work we argue that the most profound role in the shaping of the short-wavelength edge of the continuum is played by the effect of radiation trapping in a gravity-like potential created by accelerating solitons. The underlying physics of this effect has a straightforward analogy with the inertial forces acting on an observer moving with a constant acceleration.