Integrated diffractive optical elements for optical sensors applications

The paper presents design, modeling, fabrication and analysis of integrated diffractive optical elements (DOEs) for optical sensor applications. The sensors presented depend on two major mechanisms: Surface Plasmon Resonance (SPR) and Guided Mode Resonance (GMR). In SPR-based sensor, DOEs are implemented on the backside of the sensor chip for an in/out coupler at large angle of operation. The proposed scheme introduces a compact optical system, while the resolution maintains no more than 10 -5 RIU. In GMR-based sensor, the novel structure is proposed to increase the sensor's sensitivity. The device geometry comprises of a sensing region (cladding layer) embedded between a sub-wavelength grating and a high index film. The changes of the sensing region optical properties influent the phase matching condition between the diffracted wave and the guided/cladding mode and hence resonance shifts. The sensitivity is directly proportional to the power confinement inside the sensing region. With a proper modal excitation, the sensitivity can be dramatically enhanced up to 32 times.