Two-finger (TF) spudt cells

SPUDT cells including two fingers only are hitherto known for so-called NSPUDT directions. In this case, usual solid-finger cells are used. The purpose of the present paper is to find SPUDT cell types consisting of two fingers only for pure mode directions. Moreover, SPUDT cells composed of two fingers suited to complete imperfect NSPUDT behavior or to compensate that are to be found. TF cells for pure mode directions on substrates like 128degYX LiNbO₃, YZ LiNbO₃ and STX quartz were found by means of an optimization procedure. The forward direction of a TF-cell SPUDT on 128degYX LiNbO₃ was determined experimentally. The properties of the new cells are compared with those of conventional SPUDT cells. The reflectivity of TF cells on 128degYX LiNbO₃ turns out to be two up to three times larger than that of DART and Hanma-Hunsinger cells at the same metal layer thickness. Furthermore, properties of TF cells on STX and SST quartz are reported. Examples for completing and compensating imperfect NSPUDT behavior are given.