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

Abstract

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. TE o and TM o 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.

Electro-optical phase-change 2 × 2 switching using three- and four-waveguide directional couplers

“…1 [3] was performed at the 2100 nm wavelength, which is adopted throughout this paper. This operation was chosen for on-chip applications in the newly emerging ∼2 μm fiber-optic communications band [3]. Rather than 2000 nm, the wavelength 2100 nm is selected because the optical extinction coefficient here, k am 0.006, is smaller than the 0.009 extinction at 2000 nm.…”

“…The switching analysis in this paper is based upon knowledge of the fundamental mode effective index variation from the earlier study at 2100 nm investigating a Si/GST/Si channel with W × H cross section of 840 nm × 420 nm including 10 nm of GST and 840 nm × 205 nm doped-Si strips [3]. For the GST material, the melting point is 819 K, and the critical temperature for phase-change is 413 K, both of which are compatible with the CMOS art [13,14].…”

“…A previous study [3] dealt with a single layer of PCM embedded at the central plane of a silicon channel waveguide as is done in this paper; however, the active devices examined previously were different from the devices investigated here. The prior work [3] simulated variable optical attenuators and 2 × 2 EO switches comprised of either a Mach-Zender interferometer or a directional coupler made from two waveguides.…”

“…The prior work [3] simulated variable optical attenuators and 2 × 2 EO switches comprised of either a Mach-Zender interferometer or a directional coupler made from two waveguides. What is new here is the directional coupler made from three or four parallel waveguides.…”

Tutorial: Integrated-photonic switching structures

“…At the 2.1 µm wavelength, Liang et al 52,53 performed modeling and simulation of the PCM layer embedded in doped-silicon channels and found fairly good IL and CT metrics in both MZI and directional-coupler configurations for interaction lengths on the 40 µm scale. No confirmation of that yet.…”