arXiv subjects

Yanlin Ke

Publications and source records attributed to Yanlin Ke.

8 recordsLinked to original sources

arXiv2026

Mitigating Electrode-Induced Polarization Artifacts in Miniaturized Terahertz Detectors via a Ring-Shaped Electrode Design

Terahertz (THz) polarization detection provides critical insights into material properties but faces a fundamental constraint upon miniaturization: subwavelength metallic electrodes induce strong localization and distortion of the incident field, thereby convoluting the intrinsic device response with electrode-induced artifacts. Here, we overcome this limitation with a ring-shaped electrode architecture that suppresses field perturbations across a broad bandwidth from 2.0 to 5.0 THz. The resonant frequency of the ring electrode can be flexibly detuned from the target operation frequency by adjusting its inner and outer radii, while the smooth, edge-free geometry minimizes the lightning-rod effect. These design features collectively lead to a pronounced suppression of localized THz field enhancement. Numerical simulations reveal an 8.48x reduction in the local field strength compared with conventional rod-shaped electrodes. Consistent with this, experimental measurements on graphene-based detectors exhibit a 6.95x decrease in photocurrent for the ring-shaped electrode relative to the rod-shaped configuration. Moreover, the ring geometry effectively reduces the linear polarization ratio of the photocurrent from >3 to <1.4, confirming its effectiveness in mitigating electrode-induced polarization anisotropy. Our design decouples the detection response from electrode-induced artifacts, enabling compact THz detectors that preserve intrinsic signal fidelity for high-quality polarization-resolved imaging and diagnostics.

physics.optics↗

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

Deep Learning Empowered Sub-Diffraction Terahertz Backpropagation Single-Pixel Imaging

Terahertz single-pixel imaging (THz SPI) has garnered widespread attention for its potential to overcome challenges associated with THz focal plane arrays. However, the inherently long wavelength of THz waves limits imaging resolution, while achieving subwavelength resolution requires harsh experimental conditions and time-consuming processes. Here, we propose a sub-diffraction THz backpropagation SPI technique. We illuminate the object with continuous-wave 0.36-THz radiation ({\lambda}0 = 833.3 {\mu}m). The transmitted THz wave is modulated by prearranged patterns generated on a 500-{\mu}m-thick silicon wafer and subsequently recorded by a far-field single-pixel detector. An untrained neural network constrained with the physical SPI process iteratively reconstructs the THz images with an ultralow sampling ratio of 1.5625%, significantly reducing the long sampling times. To further suppress the THz diffraction-field effects, a backpropagation SPI from near field to far field is implemented by integrating with a THz physical propagation model into the output layer of the network. Notably, using the thick wafer where THz evanescent field cannot be fully recorded, we achieve a spatial resolution of 118 {\mu}m (~{\lambda}0/7) through backpropagation SPI, thus eliminating the need for ultrathin photomodulators. This approach provides an efficient solution for advancing THz microscopic imaging and addressing other inverse imaging challenges.

eess.IV↗

arXiv2021

Tunable Hyperbolic Phonon Polaritons in a Gradiently-Suspended Van Der Waals α-MoO3

Highly confined and low-loss hyperbolic phonon polaritons (HPhPs) sustained in van der Waals crystals exhibit outstanding capabilities of concentrating long-wave electromagnetic fields deep to the subwavelength region. Precise tuning on the HPhP propagation characteristics remains a great challenge for practical applications such as nanophotonic devices and circuits. Here, we show that by taking advantage of the varying air gaps in a van der Waals α-MoO3 crystal suspended gradiently, it is able to tune the wavelengths and dampings of the HPhPs propagating inside the α-MoO3. The results indicate that the dependences of polariton wavelength on gap distance for HPhPs in lower and upper Reststrahlen bands are opposite to each other. Most interestingly, the tuning range of the polariton wavelengths for HPhPs in the lower band, which exhibit in-plane hyperbolicities, is wider than that for the HPhPs in the upper band of out-of-plane hyperbolicities. A polariton wavelength elongation up to 160% and a reduction of damping rate up to 35% are obtained. These findings can not only provide fundamental insights into manipulation of light by polaritonic crystals at nanoscale, but also open up new opportunities for tunable nanophotonic applications.

physics.optics↗

arXiv2021

Controlling and focusing of in-plane hyperbolic phonon polaritons in α-MoO3 with plasmonic antenna

Hyperbolic phonon polaritons (HPhPs) sustained in van der Waals (vdW) materials exhibit extraordinary capabilities of confining long-wave electromagnetic fields to the deep subwavelength scale. In stark contrast to the uniaxial vdW hyperbolic materials such as hexagonal boron nitride (h-BN), the recently emerging biaxial hyperbolic materials such as α-MoO3 and α-V2O5 further bring new degree of freedoms in controlling light at the flatland, due to their distinctive in-plane hyperbolic dispersion. However, the controlling and focusing of such in-plane HPhPs are to date remain elusive. Here, we propose a versatile technique for launching, controlling and focusing of in-plane HPhPs in α-MoO3 with geometrically designed plasmonic antennas. By utilizing high resolution near-field optical imaging technique, we directly excited and mapped the HPhPs wavefronts in real space. We find that subwavelength manipulating and focusing behavior are strongly dependent on the curvature of antenna extremity. This strategy operates effectively in a broadband spectral region. These findings can not only provide fundamental insights into manipulation of light by biaxial hyperbolic crystals at nanoscale, but also open up new opportunities for planar nanophotonic applications.

physics.optics↗

arXiv2020

Polariton Waveguide Modes in Two-Dimensional Van der Waals Crystals: An Analytical Model and Correlative Scanning Near-Field Optical Microscopy Studies

Two-dimensional van der Waals (vdW) crystals can sustain various types of polaritons with strong electromagnetic confinements, making them highly attractive for the nanoscale photonic and optoelectronic applications. While extensive experimental and numerical studies are devoted to the polaritons of the vdW crystals, analytical models are sparse. Particularly, applying such a model to describe the polariton behaviors visualized by state-of-art near-field optical microscopy requires further investigation. Herein, we develop an analytical waveguide model to describe the polariton propagations in vdW crystals. The dispersion contours, dispersion relations, and electromagnetic field distributions of different polariton waveguide modes are derived. The model is verified by near-field optical imaging and numerical simulation of phonon polaritons in the α-MoO3, a typical vdW biaxial crystals. The model can be extended to other types of polaritons in vdW crystals, thus allowing for describing and understanding their localized electromagnetic behaviors analytically.

physics.optics↗

arXiv2018

A mid-infrared biaxial hyperbolic van der Waals crystal

Hyperbolic media have attracted much attention in the photonics community, thanks to their ability to confine light to arbitrarily small volumes and to their use for super-resolution applications. The 2D counterpart of these media can be achieved with hyperbolic metasurfaces, which support in-plane hyperbolic guided modes thanks to nanopatterns which, however, pose significant fabrication challenges and limit the achievable confinement. We show that thin flakes of the van der Waals material α-MoO3 can support naturally in-plane hyperbolic polariton guided modes at mid-infrared frequencies without any patterning. This is possible because α-MoO3 is a biaxial hyperbolic crystal, with three different Restrahlen bands, each for a different crystal axis. Our findings can pave the way towards new paradigm to manipulate and confine light in planar photonic devices.

physics.optics↗