Integrated strip and slot waveguides in silicon-on-sapphire for mid infrared VOC detection in water

A chip integrated infrared spectrometer for in situ sensing and spectroscopic identification of VOCs in water probing large absorption cross sections of VOCs in the mid-infrared is desired. Preliminary strip and slot waveguide devices fabricated in silicon-on-sapphire for operation at 3.4μm wavelength experimentally demonstrated propagation loss of 2.1dB/cm for strip waveguides and 11dB/cm for slot waveguide. VOC are extracted from water using PDMS for solid phase micro-extraction and enables absorbance measurements independent from the strong absorbance of water. Absorbance of xylene as a typical VOC is determined on chip from the difference in transmitted intensity in the presence and absence of xylene.

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