Characterization of rectangular glass micro-capillaries by low-coherence reflectometry

We report the functionality of optical low-coherence reflectometry (OLCR) to characterize glass micro-capillaries with 50-μm deep rectangular cross section, in view of their application as microoptofluidic devices. We exploited infrared radiation generated by a tungsten lamp in a time-domain low-coherence interferometer based on a fiberoptic Michelson scheme. OLCR allowed us to easily detect the optical distance between in-depth interfaces of the capillary as well as the refractive index of ethylene glycol solutions in water at different concentrations, which were inserted into the channel by capillary action.