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.

Quantifying Information via Shannon Entropy in Spatially Structured Optical Beams

While information is ubiquitously generated,shared,and analyzed in a modern-day life,there is still some controversy around the ways to assess the amount and quality of information inside a noisy optical channel.A number of theoretical approaches based on,e.g.,conditional Shannon entropy and Fisher information have been developed,along with some experimental validations.Some of these approaches are limited to a certain alphabet,while others tend to fall short when considering optical beams with a nontrivial structure,such as Hermite-Gauss,Laguerre-Gauss,and other modes with a nontrivial structure.Here,we propose a new definition of the classical Shannon information via the Wigner distribution function,while respecting the Heisenberg inequality.Following this definition,we calculate the amount of information in Gaussian,Hermite-Gaussian,and LaguerreGaussian laser modes in juxtaposition and experimentally validate it by reconstruction of the Wigner distribution function from the intensity distribution of structured laser beams.We experimentally demonstrate the technique that allows to infer field structure of the laser beams in singular optics to assess the amount of contained information.Given the generality,this approach of defining information via analyzing the beam complexity is applicable to laser modes of any topology that can be described by well-behaved functions.Classical Shannon information,defined in this way,is detached from a particular alphabet,i.e.,communication scheme,and scales with the structural complexity of the system.Such a synergy between the Wigner distribution function encompassing the information in both real and reciprocal space and information being a measure of disorder can contribute into future coherent detection algorithms and remote sensing.

Quantifying Information via Shannon Entropy in Spatially Structured Optical Beams

While information is ubiquitously generated,shared,and analyzed in a modern-day life,there is still some controversy around the ways to assess the amount and quality of information inside a noisy optical channel.A number of theoretical approaches based on,e.g.,conditional Shannon entropy and Fisher information have been developed,along with some experimental validations.Some of these approaches are limited to a certain alphabet,while others tend to fall short when considering optical beams with a nontrivial structure,such as Hermite-Gauss,Laguerre-Gauss,and other modes with a nontrivial structure.Here,we propose a new definition of the classical Shannon information via the Wigner distribution function,while respecting the Heisenberg inequality.Following this definition,we calculate the amount of information in Gaussian,Hermite-Gaussian,and LaguerreGaussian laser modes in juxtaposition and experimentally validate it by reconstruction of the Wigner distribution function from the intensity distribution of structured laser beams.We experimentally demonstrate the technique that allows to infer field structure of the laser beams in singular optics to assess the amount of contained information.Given the generality,this approach of defining information via analyzing the beam complexity is applicable to laser modes of any topology that can be described by well-behaved functions.Classical Shannon information,defined in this way,is detached from a particular alphabet,i.e.,communication scheme,and scales with the structural complexity of the system.Such a synergy between the Wigner distribution function encompassing the information in both real and reciprocal space and information being a measure of disorder can contribute into future coherent detection algorithms and remote sensing.