Ultrafast investigations of slow light in photonic crystal structures

Optical structures with dimensions down to nanometer length scales have been a topic for investigation for an increasing number of researchers, due to their intriguing physical properties and their possible new optical applications. In this thesis, waveguides in two-dimensional photonic crystals are investigated. Since the waveguide is embedded in a periodic medium, these waveguide can also have spectacular properties such as the ability to slow down light. For a full understanding of the intricate interaction of light and geometry - that may change on the subwavelength scale - the optical field should also be monitored on this scale. To this end, a time-resolving phase-sensitive near-field microscope was used. Using the phase-sensitive and time resolved information on the flow of light, the dispersion relation could be recovered, proving that light may slow down in photonic crystal waveguides. The degree to which light slows down is limited to the quality of the photonic crystal structure and can be controlled down to velocities of c/30. The time-resolved investigation also show the strong dispersive effects of photonic crystal waveguides and even the evolution of light pulses in composite photonic crystal devices.