Abstract
Due to the remarkable properties of chalcogenide (Chg) glasses, Chg optical waveguides should play a significant role in the development of optical biosensors. This paper describes the fabrication and properties of chalcogenide fibres and planar waveguides. Using optical fibre transparent in the mid-infrared spectral range we have developed a biosensor that can collect information on whole metabolism alterations, rapidly and in situ. Thanks to this sensor it is possible to collect infrared spectra by remote spectroscopy, by simple contact with the sample. In this way, we tried to determine spectral modifications due, on the one hand, to cerebral metabolism alterations caused by a transient focal ischemia in the rat brain and, in the other hand, starvation in the mouse liver. We also applied a microdialysis method, a well known technique for in vivo brain metabolism studies, as reference. In the field of integrated microsensors, reactive ion etching was used to pattern rib waveguides between 2 and 300 μm wide. This technique was used to fabricate Y optical junctions for optical interconnections on chalcogenide amorphous films, which can potentially increase the sensitivity and stability of an optical micro-sensor. The first tests were also carried out to functionalise the Chg planar waveguides with the aim of using them as (bio)sensors.
Highlights
The use of chalcogenide glasses offers notable advantages such as remarkable optical properties like a wide transmission window (1–20 μm), depending on composition, high refractive indices, which allow a high portion of the light to be concentrated outside of the core material, making them suitable for sensitive detection of clinical or environmental changes [1,2,3,4,5,6,7,8,9,10]
They present interesting nonlinear optical properties, photorefractive effects, low phonon energies for active devices related to photoluminescence, explored on bulk glasses and on fibres and planar waveguides [11,12,13,14,15,16,17,18,19]
For some 10 years infrared transmitting optical fibres have been especially designed to carry out a new spectroscopic technique called Fibre Evanescent Wave Spectroscopy (FEWS) [3,4,10,20]
Summary
The use of chalcogenide glasses offers notable advantages such as remarkable optical properties like a wide transmission window (1–20 μm), depending on composition, high refractive indices, which allow a high portion of the light to be concentrated outside of the core material, making them suitable for sensitive detection of clinical or environmental changes [1,2,3,4,5,6,7,8,9,10] They present interesting nonlinear optical properties, photorefractive effects, low phonon energies for active devices related to photoluminescence, explored on bulk glasses and on fibres and planar waveguides (wavelength conversion, Raman and parametric amplification, laser sources for mid-IR ...) [11,12,13,14,15,16,17,18,19]. Some results concerning medical applications will be presented
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