Three novel integrated optical sensing structures for the chemical domain

The performance of three novel integrated optical sensing structures is explored theoretically. The basic structure is a strip-loaded waveguide in which the strip consists of a several nanometers thick sensitive material. An attractive option is to realize this strip as a monomolecular antibody layer making the sensor capable to monitor chemical concentrations. All sensing structures rely on measurand induced changes of the field profile of the probing guided mode; this is in contrast to the big majority of the refractive IO-sensors in which the changes of the effective refractive index Neff are exploited. The potential of all sensing structures have been analyzed theoretically with a strong focus on obtaining good resolutions taking into account the effects of the imperfectness of the peripheral equipment. Resolutions expressed in terms of changes of the effective thickness in the range 10−3–3 × 10−5 nm are expected to be feasible. Optical chips containing apart from the sensing structures also reference branches and fiber to chip couplings are discussed. A technological process for realizing the sensors in SiON technology is proposed.