Non-volatile quasi-continuously programmable silicon photonics using phase-change materials (Conference Presentation)

With silicon photonics going fabless, large-scale silicon photonic integrated circuits (PICs) have recently become a reality. Many of these PICs feature system reconfigurability to benefit from the cost-effective mass manufacture of a universal platform. However, reconfigurable silicon PICs relying on the weak, volatile thermo-optic or electro-optic effect of silicon usually suffer from a large footprint and energy consumption. Recently, phase-change materials have shown great promise for energy-efficient, ultra-compact and ultra-fast non-volatile integrated photonic applications. Here, by integrating phase-change materials, Ge2Sb2Te5 (GST) with silicon microring resonators, we demonstrate a non-volatile, programmable, energy-efficient, and compact platform over the telecommunication range. By measuring and fitting the output spectra of the microrings covered with various lengths of GST in the amorphous and crystalline states, we characterize the strong broadband attenuation (~7.3 dB/μm) and optical phase (~0.70 nm/μm) modulation effects of the platform. By adjusting the energy and number of free-space laser pulses applied to the GST, we perform reversible and quasi-continuous tuning of the GST state, and the subsequent tuning of the attenuation and resonance of the microring resonators enabled by the thermo-optically-induced phase changes. Designed to achieve near critical coupling of the microring resonators when the GST is in the amorphous state, a non-volatile 1×1 optical switch with high extinction ratio as large as 33 dB is demonstrated. Our research constitutes the first step towards future large-scale programmable silicon PICs. With appropriate design, a broadband low-loss 2×2 optical switch could be electrically controlled which would be the building block for a future non-volatile routing network and optical FPGA. Reference: J. J. Zheng, A. Khanolkar, P. P. Xu, S. Deshmukh, J. Myers, J. Frantz, E. Pop, J. Hendrickson, J. Doylend, N. Boechler, and A. Majumdar, "GST-on-silicon hybrid nanophotonic integrated circuits: a non-volatile quasi-continuously reprogrammable platform," Opt. Mater. Express 8(6), 1551-1561 (2018).