arXiv subjects

Shangdong Li

Publications and source records attributed to Shangdong Li.

7 recordsLinked to original sources

arXiv2026

Deep-Subwavelength Plasmon Polariton Atomic Cavity Detector for Frequency- and Polarization-Sensitive Terahertz Detection and Imaging

Room-temperature, miniaturized, polarization-resolved terahertz (THz) detection of high speed is vital for high-resolution imaging in radar, remote sensing, and semiconductor inspection, and is essential for large-scale THz focal plane arrays. However, miniaturization below deep-subwavelength scales (< 1/50 wavelength) remain challenging due to weak light-matter interaction, which degrades responsivity and polarization sensitivity. Here, we present a graphene plasmon polariton atomic cavity (PPAC) monolithic detector that overcomes this limitation by maintaining and even enhancing performance at a deep-subwavelength channel length of just 2 micrometers (1/60 wavelength). The device integrates graphene rectangle PPAC arrays with dissimilar metal contacts, where graphene functions as both absorber and conductor, simplifying the architecture. Exploiting plasmon polariton resonances and the photothermoelectric (PTE) effect, the detector achieves polarization-sensitive, frequency-selective, and fast THz detection spanning 0.53 to 4.24 THz with a polarization ratio of 93, featuring a responsivity (RV) of 1007 V/W, a noise-equivalent power (NEP) of 16 pW/Hz^0.5, a specific detectivity (D*) of 2.9 x 10^7 Jones, and a response time of 230 ps. We further demonstrate monolithic integration for polarization imaging and non-destructive semiconductor chip inspection, advancing room-temperature, compact, and polarization-sensitive THz technologies.

physics.optics↗

arXiv2025

A two-dimensional terahertz smart wristband for integrated sensing and communication

The development of wearable devices for terahertz (THz) integrated sensing and communication (ISAC) is pivotal for forthcoming 6G Internet of Things (IoT) and wearable optoelectronics. However, existing THz system suffers from bulkiness, narrow spectral response and limited flexibility constrained by their dependence on external antennas, complex coupling architectures and rigid components. Here, we present a 2D THz smart wristband based on a graphene plasmon polariton atomic cavity (PPAC) array, which integrates sensing and communication within a monolithic microdetector. Operating without any external antenna, the compact and flexible device enables self-powered, polarization-sensitive and frequency-selective THz detection across a broad response spectrum from 0.25 to 4.24 THz, with a responsivity of 6 V/W, a response time of 62 ms, and mechanical robustness maintained over 2000 bending cycles. Notably, we further exploit its multi-parameter THz responses for dual-purpose ISAC functionality. For sensing, the polarization- and strain-dependent THz responses are utilized as high-dimensional features for a convolutional neural network (CNN), enabling circuit fault diagnosis with 97% accuracy. For communication, the device implements secure encrypted communication under simulated on-body wearing condition through dual-channel encoding of THz polarization and on-off signals. This 2D ISAC platform paves the way for miniaturized, intelligent wearable systems for advanced human-machine interaction.

physics.optics↗

arXiv2025

Coherent Absorption Synergizes with Plasmon-Enhanced Graphene Terahertz Photo-thermoelectric Response

Terahertz (THz) technology shows great potential in 6G communications and imaging, but faces challenges related to detector sensitivity, noise, and cryogenic operation. Here, we integrate interferometric enhancement of absorption (IEA) from a metal reflection layer with a graphene plasmon polariton atomic cavity (PPAC)-based photodetector. The hybrid configuration enhances the in-plane electric field and improves the plasmon-induced thermal gradient. Numerical simulations and photoresponse measurements were employed to systematically investigate the influence of a metal reflective layer on the photothermoelectric behavior of the device, which reveals the IEA design significantly boosts the THz absorption rate in graphene nanostructures and promotes asymmetry in the lateral diffusion of hot carriers. Compared with the bare device, the responsivity of the device is enhanced by approximately 30-folds, while maintaining a response time below 130 microseconds. We further demonstrate the potential of the device to distinguish concealed liquids, advancing high-responsivity, room-temperature, and compact terahertz imaging technology.

cond-mat.mes-hall↗

arXiv2024

Monolithic Multi-parameter Terahertz Nano-micro Detector Based on Plasmon Polariton Atomic Cavity

Terahertz signals hold significant potential for ultra-wideband communication and high-resolution radar, necessitating miniaturized detectors capable of multi-parameter detection of intensity, frequency, polarization, and phase. Conventional detectors cannot meet these requirements. Here, we propose plasmon polariton atomic cavities (PPAC) made from single-atom-thick graphene, demonstrating the monolithic multifunctional miniaturized detector. With a footprint one-tenth the incident wavelength, the detector offers benchmarking intensity-, frequency-, and polarization-sensitive detection, rapid response, and sub-diffraction spatial resolution, all operating at room temperature across 0.22 to 4.24 THz. We present the monolithic detection applications for free-space THz polarization-coded communication and stealth imaging of physical properties. These results showcase the PPAC's unique ability to achieve strong absorption and weak signal detection with a thickness of only 10^-5 of the excitation wavelength, which is inaccessible with other approaches.

physics.app-ph↗

arXiv2024

Integrating of continuous graphene with periodic ferroelectric domains for adaptive terahertz photodetector

Graphene plasmons hold immense potential for terahertz (THz) detector application due to their fascinating interactions between radiation and matter. However, it has remained challenging to excite and manipulate graphene plasmons within continuous graphene that is free of patterning technique. Here, we report an adaptive wavelength-sensitive terahertz detector consisting of continuous graphene integrated onto a ferroelectric thin film with periodic polarization domains. This designed device is capable of absorbing THz waves with zero input bias voltage because of highly confinement of surface plasmons within the interface between graphene and ferroelectrics. By reconfiguring an interweaving squared ferroelectric domain array with alternating upward and downward polarizations, our devices theoretically own an ultrahigh responsivity of 17.56 A W-1 and a specific detectivity of 1.11*10^11 Jones at room temperature. We also demonstrate that the photodetectors make possible for spectrum reconstruction application of portable spectrometer at a broad operation band of 4.97 to 7.85 THz with resolution up to 0.02 THz combining the mathematical algorithms.

physics.optics↗

arXiv2022

Tunable plasmonic devices by integrating graphene with ferroelectric nanocavity

Graphene plasmons are able to become the fundermental of novel conceptual photonic devices, resulting from their unique characteristics containing excitation at room temperature and tunable spectral selectivity in different frequencies. The pursuit of efficiently exciting and manipulating graphene plasmons is necessary and significant for high-performance devices. Here, we investigate graphene plasmon wave propagating in ferroelectric nanocavity array. We experimentally show that the the periodic ferroelectric polarizations could be used for doping graphene into desired spatial carrier density patterns. Based on a theoretical model that considers periodic ununiform conductivity across graphene sheet, the simulation results show surface plasmon polaritons (SPP) in graphene can be excited by an incident light in a similar way to the excitation of photonic crystal resonant modes. The graphene SPP resonance can be tuned from ~720 to ~1 000 cm-1 by rescaling the ferroelectric nanocavity array, and from ~540 to ~780 cm-1 by dynamically changing the applied gate voltage. Our strategy of graphene carrier engineering to excite SPP offers a promissing way for large-scale, non-destructive fabrication of novel graphene photonic devices.

physics.optics↗

arXiv2022

Ferroelectric superdomain controlled graphene plasmon for tunable mid-infrared photodetector with dual-band spectral selectivity

Dual-band infrared photodetectors (DBIPs) can discriminate desired signals from complex scenes and thus are highly expected for threat-warning, remote sensing, and astronomy applications. Conventional DBIPs with high-performances are, however, typically based on semiconductor thin films, but remain the challenges of complex spatial align, expensive growth and cooling requirement. Here, we report a tunable graphene plasmonic photodetector with dual-band infrared spectral selectivity driven by ferroelectric superdomain. The periodic ferroelectric polarization array with nanoscale ring shapes provides ultrahigh electrostatic field for spatially doping of monolayer graphene to desired patterns, and is further used to excite and confine intrinsic graphene plasmons. Our devices exhibit tunable resonance photoresponse in both two bands of 3.7-16.3 um and 15.1-52.1 um. The numerical calculations show that our devices own ultrahigh responsivities of 667-1080 A W-1 at room temperature in range of 5-50 um. Our devices make possible the applications of infrared imaging system and both stationary and motion state of objects detection. These investigations provide a novel approach for advanced infrared system construction by employing simple, low-cost, uncooling multispectral detectors array.

physics.optics↗