Abstract

This theoretical modeling and simulation paper presents designs and projected performance of non-volatile broadband on-chip 1 × 2 and 2 × 2 electro-optical switches operating in the telecommunication C-band and based on the silicon-on-insulator technological platform. These optical switches consist of an asymmetric two-waveguide directional coupler and a symmetric three-waveguide directional coupler, in which the optical phase change material Ge₂Sb₂Se₄Te₁ (GSST) is the top cladding layer for one of the silicon strip waveguides. Reversible crossbar switching is attained by the amorphous (Am) to crystalline (Cr) and Cr-to-Am phase transitions in the GSST induced by heating the GSST in contact with an indium tin oxide (ITO) microstrip through Joule heating. We examined device performance in terms of mid-band insertion loss (IL), crosstalk (CT), and 0.3-dB IL bandwidth (BW). The 2 × 2 results were IL = –0.018 dB, CT < 31.3 dB, and BW = 58 nm for the coupling length L_c of 15.4 μm, and IL = 0.046 dB, CT < 38.1 dB, and BW = 70 nm for the coupling length L_c of 17.4 μm. Simulations of the 1 × 2 devices at 16.7-μm L_c revealed that IL = 0.083 dB and CT < 12.8 dB along with an expanded BW of 95 nm. Thermal simulations showed that a 5-V pulse train applied to 10¹⁹-cm⁻³ doped ITO would produce crystallization; however, the process of amorphization required a 24-V pulse of 2.9-μs duration to raise the GSST temperature above the melting temperature of 900 K.

© 2019 IEEE

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