Miniature Multilevel Optical Memristive Switch Using Phase Change Material

Abstract

The optical memristive switches are electrically activated optical switches that can memorize the current state. They can be used as optical latching switches in which the switching state is changed only by applying an electrical Write/Erase pulse and maintained without external power supply.We demonstrate an optical memristive switch based on a silicon MMI structure covered with nanoscale-size Ge2Sb2Te5 (GST) material on top. The phase change of GST is triggered by resistive heating of the silicon layer beneath GST with an electrical pulse. Experimental results reveal that the optical transmissivity can be tuned in a controllable and repeatable manner with the maximum transmission contrast exceeding 20 dB. Partial crystallization of GST is obtained by controlling the width and amplitude of the electric pulses. Crucially, we also demonstrate that both Erase and Write operations, to and from any intermediate level, are possible with accurate control of the electrical pulses. Our work marks a significant step forward towards realizing photonic memristive switches without static power consumption, which are highly demanded in highdensity large-scale integrated photonics.

Experimental investigation of silicon and silicon nitride platforms for phase-change photonic in-memory computing

“…Phase-change optical memory (PCOM) photonics has also been applied to photonic computing and artificial neural networks, such as implementation of accumulative addition [38], multiplication [39], optical synapses [40], and most recently, deep-learning neurosynaptic networks for image recognition [41]. Recently, there has also been work on developing phase-change photonics using GST on Si waveguides [35,42,43]. Thus, both Si and SiN have been employed, although these two platforms have very distinct optical properties as well as relative advantages, both in the linear and nonlinear regimes.…”

Nonvolatile Electrically Reconfigurable Integrated Photonic Switch Enabled by a Silicon PIN Diode Heater

“…[ 25 ] Besides, PCMs are highly scalable [ 26 ] and can be simply deposited via sputtering onto any substrate without the “lattice mismatch” issue. Consequently, PCMs have already been used in compact, low‐energy, and broadband programmable PICs for switches, [ 15,27–33 ] memories, [ 2,34 ] and computing. [ 35–38 ] However, scalable control over the states of PCMs for a chip‐scale PIC system of a much higher complexity is yet to be resolved.…”

Tunable nanophotonics enabled by chalcogenide phase-change materials

“…Accordingly, these approaches cannot be practical for large-scale integration. To address these limitations, recently, electro-thermal-optic [222,223,228,229] and mixed-mode electrical/optical [224,226] Figure 16A) [222]. The thickness of ITO was optimized to be 30 nm to reduce the switching energy while keeping the ER above 30 dB.…”

“…On the other hand, by re-crystallization of both GST patches using a 100 ms pulse of 12 mA, the probe light is highly absorbed resulting in a low optical transmission (off-state). An Figure 16B), which can be set/reset by employing electrical pulses [223,228]. The top panels in Figure 16B show the structure of the switch in which a Si strip orthogonally crosses the center of the MMI, and is heavily P ++ -doped at the center, where GST presents.…”