Electrical programmable multilevel nonvolatile photonic random-access memory

Photonic Random-Access Memories(P-RAM)are an essential component for the on-chip non-von Neumann photonic computing by eliminating optoelectronic conversion losses in data links.Emerging Phase-Change Materials(PCMs)have been showed multilevel memory capability,but demonstrations still yield relatively high optical loss and require cumbersome WRITE-ERASE approaches increasing power consumption and system package challenges.Here we demonstrate a multistate electrically programmed low-loss nonvolatile photonic memory based on a broadband transparent phase-change material(Ge2Sb2Se5,GSSe)with ultralow absorption in the amorphous state.A zero-staticpower and electrically programmed multi-bit P-RAM is demonstrated on a silicon-on-insulator platform,featuring efficient amplitude modulation up to 0.2 dB/μm and an ultralow insertion loss of total 0.12 dB for a 4-bit memory showing a 100×improved signal to loss ratio compared to other phase-change-materials based photonic memories.We further optimize the positioning of dual microheaters validating performance tradeoffs.Experimentally we demonstrate a half-a-million cyclability test showcasing the robust approach of this material and device.Low-loss photonic retention-of-state adds a key feature for photonic functional and programmable circuits impacting many applications including neural networks,LiDAR,and sensors for example.

Self-driven highly responsive p-n junction In Se heterostructure near-infrared light detector

Photodetectors converting light signals into detectable photocurrents are ubiquitously in use today.To improve the compactness and performance of next-generation devices and systems,low dimensional materials provide rich physics to engineering the light-matter interaction.Photodetectors based on two-dimensional(2D)material van der Waals heterostructures have shown high responsivity and compact integration capability,mainly in the visible range due to their intrinsic bandgap.The spectral region of near-infrared(NIR)is technologically important,featuring many data communication and sensing applications.While some initial NIR 2D material-based detectors have emerged,demonstrations of doping-junction-based 2D material photodetectors with the capability to harness the charge-separation photovoltaic effect are yet outstanding.Here,we demonstrate a 2D p-n van der Waals heterojunction photodetector constructed by vertically stacking p-type and n-type indium selenide(In Se)flakes.This heterojunction charge-separation-based photodetector shows a threefold enhancement in responsivity in the NIR spectral region(980 nm)as compared to photoconductor detectors based on p-or n-only doped In Se.We show that this junction device exhibits self-powered photodetection operation,exhibits few p A-low dark currents,and is about 3-4 orders of magnitude more efficient than the state-of-the-art foundry-based devices.Such capability opens doors for low noise and low photon flux photodetectors that do not rely on external gain.We further demonstrate millisecond response rates in this sensitive zero-bias voltage regime.Such sensitive photodetection capability in the technologically relevant NIR wavelength region at low form factors holds promise for several applications including wearable biosensors,three-dimensional(3D)sensing,and remote gas sensing.