Simulations of Silicon-on-Insulator Channel-Waveguide Electrooptical 2 × 2 Switches and 1 × 1 Modulators Using a ${\bf Ge_2}{\bf Sb_2}{\bf Te_5}$ Self-Holding Layer

This paper reports theoretical designs and simulations of electrooptical 2 × 2 switches and 1 × 1 loss modulators based upon GST-embedded SOI channel waveguides. It is assumed that the amorphous and crystalline phases of GST can be triggered electrically by Joule heating current applied to a 10-nm GST film sandwiched between doped-Si waveguide strips. TEo and TMo mode effective indices are calculated over 1.3 to 2.1-μm wavelength range. For 2 × 2 Mach-Zehnder and directional coupler switches, low insertion loss, low crosstalk, and short device lengths are predicted for 2.1 μm, although a decreased performance is projected for 1.55 μm. For 1.3-2.1 μm, the 1 × 1 EO waveguide has application as a variable optical attenuator and as a digital modulator, albeit with ≤100-ns state-transition time. Because the active material has two “stable” phases, the device holds itself in either state, and voltage needs to be applied only during transition.