Fabrication of Silicon-Blazed Gratings for Couplers

To our knowledge, no blazed grating has been fabricated in silicon (Si) at a pitch of less than half a micron. In this article, we report the fabrication of Si-blazed gratings at the period of 400 nm, using electron beam lithography and ion beam etching techniques. The blazed grating is extremely useful as a grating coupler in integrated optics, operating at the telecommunication wavelength of 1.3 mum, because very high output efficiency of the grating coupler is expected. This will allow coupling to thin film devices in silicon, previously not regarded as promising because coupling to them was very inefficient.