| 摘要 |
PURPOSE:To sufficiently restore the physical constant of an LiNbO3 substrate by a heat treatment after a proton exchange and to surely improve characteristics, such as acousto-optical(AO) diffraction efficiency and electro- optical diffraction efficiency, as well by setting the thickness of a proton exchange layer before the heat treatment at a specific range. CONSTITUTION:The thickness of the proton exchange layer prior to the heat exchange is previously set in the 20 to 200nm range. The reason thereof lies in that the AO diffraction efficiency degrades drastically if the thickness is outside the above-mentioned range. The formation of the proton exchange layer 10 is executed by first storing pyrophosphoric acid in a platinum crucible, maintaining this acid at a prescribed temp. and immersing the LiNbO3 substrate 11 therein for a prescribed period of time, thereby effecting the H<+> (proton) exchange. The thickness of the proton exchange layer is adjusted to, for example, 158nm by controlling the time for the proton exchange treatment. The substrate 11 is then washed to wash away the acid and is dried; thereafter, the substrate is heat treated under conditions of 350 deg.CX1 hour, by which H<+> is diffused and the thin film optical waveguide 10 is obtd. |
