advantage is that SWTGs are made of amorphous materials and can be monolithically fabricated anywhere on a wafer.  The first properties makes SWTGs suitable for high speed applications w here the cavity length is a limiting factor.

Picture will be added soon.

Measured(dots) and simulated (solid lines) phase retardation between TE and TM waves (l=677nm) through a 180nm thick a-Si grating.

The second property makes SWTGs suitable for large area  integrated optics, which are a key to future telecommunications and integrated circuit interconnections.