Structural disorder induced polarization and mode scrambling in Photonic Crystals

The authors investigates the impact of structural disorder in line-defect photonic crystal waveguides through optical low-coherence reflectometry (OLCR). The potential of photonic crystal waveguides for dispersion engineering and, in particular, controlling the propagation delay was realised very early, however, the practical implementation of this beautiful concept had been hampered by severe technological and also theoretical difficulties, leading to unacceptable propagation losses. More recently, the proper design of line-defect waveguides on 2D Photonic Crystal slabs allowed an impressive reduction of propagation loss down to less than 10dB/cm, thus opening new perspectives in the field of optical processing. However, fabrication defects and, in particular, structural disorder and roughness still have a strong impact on propagation as the group velocity is decreased. Therefore, understanding disorder appears as a critical task in view of implementation of slow-light with photonic crystal technology.