Broadband light sources with liquid core

1 min read

A supercontinuum light source has been generated using liquid core optical fibres, says a team from the Leibniz Institute of Photonic Technology, the Fraunhofer Institute of Applied Optics and Precision Mechanics, the Friedrich Schiller University of Jena, and the Helmholtz Institute Jena.

The researchers ‘shot’ a hybrid waveguide with an ultrafast, intense laser pulse which is said to have produced a very broad light spectrum of 1.1μm to 2.7μm in the near and mid-infrared range.

According to the team, the coupled, ultrafast light pulse breaks up into solitons due to non-linear interactions with matter in the optical fibre. This is said to form the broadband laser light that is indispensable as a supercontinuum light source for applications in medical imaging, measurement technology and spectroscopy.

However, not many materials show nonlinear optical effects and, at the same time, exhibit sufficient light transmission in the infrared spectral range.

"To resolve this issue, the fibre core was filled with carbon disulphide, a liquid chemical compound with a very high refractive index,” explained Mario Chemnitz, scientist at the Leibniz Institute. “If we then couple polarised light into the core, the carbon disulphide molecules orient themselves along the electromagnetic field of the light.

“Due to this molecular orientation, the optical density – and thus the light transmission in the fibre – varies according to the intensity of the laser light."

One unique feature of carbon disulphide is that the molecules orient themselves with a certain time delay.

According to the team, this characteristic reduces fluctuations in the spectral bandwidth of the supercontinuum light source and makes liquid core fibres a more stable alternative to the known broadband light sources based on optical fibres made from special glasses.