The currently faced biggest challenge in integrated optics (IO) is finding or developing materials that can be used as active components for optical circuits. In order for a material to be considered for IO applications, it has to possess optimal non-linear optical (NLO) properties, such as a large light-induced refractive index change, but also mechanical stability. In my thesis, I investigated the photoactive yellow protein (PYP) with various experimental methods to assess the protein’s IO applicability. During the measurements, a glycerol-doped (GL) PYP film was used to maintain high mechanical stability and optical homogeneity of the investigated PYP-films. First, the kinetics of certain photocycle intermediates of PYP were monitored with absorption kinetics measurements to find the optimal environment to use the protein films in. This was followed by measuring the linear and non-linear refractive index of GL-PYP films. The NLO refractive index was investigated with the Z-scan technique as a function of excitation laser pulse parameters, i.e., average and peak intensities, and repetition rate of the pulses. For investigating the potential miniaturization and the possibility of creating homogeneous protein monolayers for further IO applications, PYP films were monitored with vibrational sum-frequency spectroscopy (VSFG). Finally, IO switching was demonstrated utilizing different photocycle intermediates. Mach- Zehnder interferometer was used for slow, while transient grating spectroscopy was applied to perform sub-ps optical switching. Based on the results, GL-PYP films are viable alternatives as IO active materials
