Flexible, reliable and simple fabrication of integrated spot size converters with shifting mask technique

The fabrication of integrated spot size converters employing standard conta ct photolithography in a novel way and dry etching technique is presented. During the exposure the mask is shifted parallel to the substrates surface. Exploiting the graduation properties the resist is not completely dissolve d, so that a vertical structure remains with a profile that can easily be p redetermined. The resist pattern is subsequently transferred into the semic onductor by means of ion beam etching. The technique has proven to be flexi ble, reliable and simple. The optical measurements of the fabricated spot s ize converters show that the loss of fibre-chip coupling is considerably re duced and the alignment tolerances are improved.