Photonic crystal fibres take the properties of traditional silica to new dimensions, from the exploitation of the high optical nonlinearities of PCF in supercontinuum generation, to the low mid-infrared attenuation of hollow core PCF, a spectral region of increasing interest for applications in spectroscopy and medicine given strong target absorption bands and the emergence of new generations of mid-IR laser sources.
The spectral attenuation of PCF (300-2700nm) and hollow core PCF (2000->4000nm) is measured by the cut-back technique using a Bentham DTMc300 triple-grating double monochromator with motorised slits, and fibre connectorised input, configured for the range 300-5000nm.
Fully automated grating control, detector selection and slit adjustment for constant bandwidth gives simple operation over this broad spectral range. The sensitive detection gives a good signal to noise even with a black body source and a single-mode fibre. In the mid-IR, the use of a cryogenically cooled InSb detector allows the accurate measurement of attenuation even in this unfavourable wavelength range.