Neuromorphic Photonic Memory Devices Using Ultrafast, Non‐Volatile Phase‐Change Materials

Abstract

The search for ultrafast photonic memory devices is inspired by the ever‐increasing number of cloud‐computing, supercomputing, and artificial‐intelligence applications, together with the unique advantages of signal processing in the optical domain such as high speed, large bandwidth, and low energy consumption. By embracing silicon photonics with chalcogenide phase‐change materials (PCMs), non‐volatile integrated photonic memory is developed with promising potential in photonic integrated circuits and nanophotonic applications. While conventional PCMs suffer from slow crystallization speed, scandium‐doped antimony telluride (SST) has been recently developed for ultrafast phase‐change random‐access memory applications. An ultrafast non‐volatile photonic memory based on an SST thin film with a 2 ns write/erase speed is demonstrated, which is the fastest write/erase speed ever reported in integrated phase‐change photonic devices. SST‐based photonic memories exhibit multilevel capabilities and good stability at room temperature. By mapping the memory level to the biological synapse weight, an artificial neural network based on photonic memory devices is successfully established for image classification. Additionally, a reflective nanodisplay application using SST with optoelectronic modulation capabilities is demonstrated. Both the optical and electrical changes in SST during the phase transition and the fast‐switching speed demonstrate their potential for use in photonic computing, neuromorphic computing, nanophotonics, and optoelectronic applications.

Millimeter‐range Induced Flexo‐Pyrophotronic Effect in Centrosymmetric Heterojunction for Ultrafast Night‐Photomonitoring

“…To check the ultrafast device operation, I py -t response to ultrafast pulses (P = 0.8 mW cm −2 ) was observed. We measured a rise time (τ r ) of 14 ns (i.e., the time it takes to rise to 63.2 percent of its maximum level), [9,17,18] allowing us to sense over 10 million bits per second (see Figure 3c). Using it, the 3-dB bandwidth estimate (i.e., the frequency at which the I py decreases to 0.707 from the corresponding maximum values, i.e., f 3dB = 0.35/τ r ) was determined to be 25 MHz.…”

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“…First, the neuron serves as the nonlinear node for summation and thresholding by the means of light source, optical amplifiers, saturable absorbers, electric-optical modulators, and photodetectors. Second, the synapse covers the weighting and memory through these devices, e.g., the microring resonators, Mach–Zehnder interferometers, and phase-change materials. Third, the dendrite provides an interconnection for network formation by waveguides.…”

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“…In this case, since the metal-insulator transition of VO 2 happens at about 340 K 120 , this material is often used for non-volatile phase transitions. Phase change materials have been exploited for various applications, including optical switching 95,103,121,122 , lensing 123 , engineered absorption 111,124,125 and thermal rectification 34,114,[126][127][128][129][130][131] .…”