Hollow glass fibres offer new applications in spectroscopy
Researchers of the Max Planck Institute (Erlangen, Germany) and of the QUEST Institute of Germany’s national metrology institution PTB (Braunschweig, Germany) developed and tested the new glass fibre with good results. They also found that this type of fibre optics could favourably be used in a number of measurement applications, including precision spectroscopy on atoms and ions as well as in optical atom clocks and in quantum computers. In addition they offers benefits in fluorescence microscopy, in testing process plasmas and in studies of burning soot and in spectroscopic studies of greenhouse gases.
Conventional fibre optics possess a solid-state core which then is coated by a material with lower optical density. The laws of physics cause the light beam is retained in such a fibre through total reflexion; the transport along the fibre occurs basically without any loss even across considerable distances. For this reason, such glass fibres are deployed globally in a number of applications to transport light in a broad spectral range from infrared to visible light. Light with a shorter wavelength however is absorbed already after a relatively short distance, and its energy has a destructive effect on the fibre glass.
The Max Planck Institute for the physics of light experiments already for some time with different fibre types. Now the researchers found out that a certain type is well suited to deal with UV light. Photonic crystal fibres with a so-called Kagomé microstructure and a hollow core with a diameter of 20µ guide UV light without getting destroyed. The term Kagomé refers to a specific pattern of regular triangles and hexagons. The hollow core conducts light in single mode – this means that it its spatial distribution resembles a Gauss distribution curve. The metrology experts from PTB’s Quest institute put the fibre through their paces and found that even after 100 hours of operation a 15mW laser at a wavelength of 280 nanometres the UV radiation did not cause any harm.
The Quest researchers even conducted a first application test in that they used the new fibres in spectroscopic studies on trapped ions. The fibre stabilised the UV ray and enabled the scientists to read out the status of the ions better than with conventional methods.
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