Molecular switch assisted planar polymer waveguide arrays for integrated optical sensing

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The aim of this project is the development of novel optical sensor concepts based on planar polymer-optical waveguide structures, which are functionalized with molecular switchable materials. The combination of these two material systems is intended to provide integrated waveguide structures with tailored optical properties that can sensitively capture physical or chemical quantities in the environment such as acidity/basicity, humidity and temperature using purely optical principles, thus, providing a new, flexible and resource-efficient class of composite materials for sensing. The change in the optical properties of the waveguide structures will be investigated as a function of various parameters: (i) the change in the spin of the tailored switchable molecular complexes (nanomaterials) which are integrated in or on the waveguide arrays for functionalization, (ii) the influence of the doping of the polymers with the switchable molecular complexes and (iii) the influence of waveguide geometry. For this purpose, it is necessary to design the switchable molecules so that they react to various external stimuli such as temperature, humidity or the mere presence of certain chemical compounds in their environment (e.g. acids or bases), i.e. a change in the refractive index, and, consequently, change their optical properties, for example, the absorption behavior or the molecular size. The resulting perturbation, in turn, affects the light propagation in the material and will be employed for optical signal generation and, thus, for sensing.The scientific challenges are: (i) the fabrication of novel polymer waveguide arrays, where light propagation is controlled by targeted insertion/application of switchable molecular complexes, (ii) the tailored anisotropic distribution of switchable molecular complexes in the waveguide structures that change the material properties and the evanescent field outside the waveguide structures, (iii) the generation of multiplex-capable structures that accumulate these switchable molecules in certain areas of the waveguides and, thus, create sensor areas of different physical and chemical quantities, as well as (iv) the exact quantification of the tailored optical properties and their evaluation for photonic applications, i.e. optical sensors or lab-on-chip systems.The ultimate goal of this project is the first-time exploitation of novel polymer fiber optic structures in combination with tailored molecular switches to control the optical properties of the resulting composite material systems and provide the foundations for new integrated optical sensor applications.