Polarization rotator terahertz photonic crystal slab waveguide

A silicon based periodic asymmetric loaded photonic crystal polarization rotator for THz frequency band has been introduced and analyzed. The polarization rotator structure consists of a single defect line photonic crystal slab waveguide with asymmetrical top cladding layer. The top cladding layer is silicon. To maintain phase matching condition, the top cladding layer is alternated on either side of the defect line periodically. Complete polarization rotation is achieved over the propagation length of 15 lambda, 7.5 mm. A new fabrication technique was developed to realize photonic crystal slab structure on SOI wafer. The fabrication process consists of deep reactive ion etching of the SOI layer and anisotropic wet etching of the handle Si layer.