GST-on-silicon hybrid nanophotonic integrated circuits: a non-volatile quasi-continuously reprogrammable platform

Abstract

Reconfiguration of silicon photonic integrated circuits relying on the weak, volatile thermo-optic or electro-optic effect of silicon usually suffers from a large footprint and energy consumption. Here, integrating a phase-change material, Ge 2 Sb 2 Te 5 (GST) with silicon microring resonators, we demonstrate an energy-efficient, compact, non-volatile, reprogrammable platform. By adjusting the energy and number of free-space laser pulses applied to the GST, we characterize the strong broadband attenuation and optical phase modulation effects of the platform, and perform quasi-continuous tuning enabled by thermooptically-induced phase changes. As a result, a non-volatile optical switch with a high extinction ratio, as large as 33 dB, is demonstrated.

Photonic In-Memory Computing Primitive for Spiking Neural Networks Using Phase-Change Materials

“…The ultra-fast switching using light overcomes the longstanding obstacle of high 'write' latencies [15] for PCMs in the electrical domain. The highly contrasting optical properties of GST in its crystalline and amorphous phases have led to implementations of allphotonic memories [22], switches [23] and reconfigurable non-volatile computing platforms [24]. More recently, photonics-based GST devices have also been explored to emulate biologically plausible synapses [25], capable of undergoing Spike Timing Dependent Plasticity (STDP), and 'integrate and fire' spiking neurons [26].…”

Metastable Refractive Index Manipulation in Hydrogenated Amorphous Silicon for Reconfigurable Photonics

“…Hence, the reversible resonance shift observed here is due to the change in the real part of the refractive index as determined from the thin‐film interferometric experiment. This is unlike the O‐PCM‐based switching devices, where high optical losses, related to the crystalline state of O‐PCM, compromise the performance of the MRR switching states . From the reversible resonant wavelength shift (Δλ res ), the effective refractive index change (Δ n eff ) can be estimated by the following equations where n g denotes the group index of the waveguide, L represents the round trip path length, and FSR (free spectral range) corresponds to the period gap between resonant wavelengths .…”

“…Among these, optical‐phase changing materials (O‐PCMs) have received significant attention in the field of reconfigurable photonics lately, as these offer on‐chip programming with a reversible change in refractive index (Δ n ) . These materials have their own limitations owing to increased optical losses due to high absorption with respect to the O‐PCM (e.g., Ge 2 Sb 2 Te 5 [GST]) switching state . Recently, some efforts have been made for realizing low‐loss programmable photonic devices with new device architectures and material combinations .…”

Towards field-programmable photonic gate arrays

“…Although the FPPGAs are expected to achieve the integration of 1000 phase actuators in the first five years, key enabling technology will be required in order to achieve this goal, efficiently. First, developing power-efficient mechanisms for the implementation of phase-shifters, possibly using nonvolatile approaches will be required to maintain a low power consumption and to enable the integration of the driving system [42]. In addition, developing efficient schemes for the monitoring and control hardware and software will be essential to supervise and manage an extensive number of TBUs in real time and improve the reconfiguration times.…”