Imaging-based terahertz pixelated metamaterials for molecular fingerprint sensing.

With the rapid development of terahertz-enabled devices, the study of miniaturized and integrated systems has attracted significant attention. We experimentally demonstrate an imaging-based pixelated metamaterial for detecting terahertz molecular fingerprints related to intermolecular vibrations and large-amplitude intramolecular modes, including chemical identification and compositional analysis. The compact THz sensor consists of a 4 × 4 pixelated filter-detector array with transmission resonances tuned to discrete frequencies.

Physics-Informed Inverse Design of Programmable Metasurfaces.

Emerging reconfigurable metasurfaces offer various possibilities for programmatically manipulating electromagnetic waves across spatial, spectral, and temporal domains, showcasing great potential for enhancing terahertz applications. However, they are hindered by limited tunability, particularly evident in relatively small phase tuning over 270°, due to the design constraints with time-intensive forward design methodologies. Here, a multi-bit programmable metasurface is demonstrated capable of terahertz beam steering facilitated by a developed physics-informed inverse design (PIID) approach.

Tamm-cavity terahertz detector.

Efficiently fabricating a cavity that can achieve strong interactions between terahertz waves and matter would allow researchers to exploit the intrinsic properties due to the long wavelength in the terahertz waveband. Here we show a terahertz detector embedded in a Tamm cavity with a record Q value of 1017 and a bandwidth of only 469 MHz for direct detection. The Tamm-cavity detector is formed by embedding a substrate with an NbN microbolometer detector between an Si/air distributed Bragg reflector (DBR) and a metal reflector.

Integrated and DC-powered superconducting microcomb.

Frequency combs, specialized laser sources emitting multiple equidistant frequency lines, have revolutionized science and technology with unprecedented precision and versatility. Recently, integrated frequency combs are emerging as scalable solutions for on-chip photonics. Here, we demonstrate a fully integrated superconducting microcomb that is easy to manufacture, simple to operate, and consumes ultra-low power.

Toroidic phase transitions in a direct-kagome artificial spin ice.

Ferrotoroidicity-the fourth form of primary ferroic order-breaks both space and time-inversion symmetry. So far, direct observation of ferrotoroidicity in natural materials remains elusive, which impedes the exploration of ferrotoroidic phase transitions. Here we overcome the limitations of natural materials using an artificial nanomagnet system that can be characterized at the constituent level and at different effective temperatures.

Near-Field Probing of Microwave Oscillators with Josephson Microscopy.

Voltage-controlled oscillators, serving as fundamental components in semiconductor chips, find extensive applications in diverse modules such as phase-locked loops, clock generators, and frequency synthesizers within high-frequency integrated circuits. This study marks the first implementation of superconducting Josephson probe microscopy for near-field microwave detection on multiple voltage-controlled oscillators. Focusing on spectrum tracking, various phenomena, such as stray spectra and frequency drifts, were found under nonsteady operating states.

Unconventional Superconducting Diode Effects via Antisymmetry and Antisymmetry Breaking.

Symmetry breaking plays a pivotal role in unlocking intriguing properties and functionalities in material systems. For example, the breaking of spatial and temporal symmetries leads to a fascinating phenomenon: the superconducting diode effect. However, generating and precisely controlling the superconducting diode effect pose significant challenges.

Linear and phase controllable terahertz frequency conversion via ultrafast breaking the bond of a meta-molecule.

The metasurface platform with time-varying characteristics has emerged as a promising avenue for exploring exotic physics associated with Floquet materials and for designing photonic devices like linear frequency converters. However, the limited availability of materials with ultrafast responses hinders their applications in the terahertz range. Here we present a time-varying metasurface comprising an array of superconductor-metal hybrid meta-molecules.

A compact multi-pixel superconducting nanowire single-photon detector array supporting gigabit space-to-ground communications.

Classical and quantum space-to-ground communications necessitate highly sensitive receivers capable of extracting information from modulated photons to extend the communication distance from near-earth orbits to deep space explorations. To achieve gigabit data rates while mitigating strong background noise photons and beam drift in a highly attenuated free-space channel, a comprehensive design of a multi-functional detector is indispensable. In this study, we present an innovative compact multi-pixel superconducting nanowire single-photon detector array that integrates near-unity detection efficiency (91.

High-timing-precision detection of single X-ray photons by superconducting nanowires.

Precisely acquiring the timing information of individual X-ray photons is important in both fundamental research and practical applications. The timing precision of commonly used X-ray single-photon detectors remains in the range of one hundred picoseconds to microseconds. In this work, we report on high-timing-precision detection of single X-ray photons through the fast transition to the normal state from the superconductive state of superconducting nanowires.

Modulo-addition operation enables terahertz programmable metasurface for high-resolution two-dimensional beam steering.

Electrically controlled terahertz (THz) beamforming antennas are essential for various applications such as wireless communications, security checks, and radar to improve coverage and information capacity. The emerging programmable metasurface provides a flexible, cost-effective platform for THz beam steering. However, scaling such arrays to achieve high-gain beam steering faces several technical challenges.

The value of using heterogeneous detector groups for the development of time-of-flight (TOF) positron emission tomography (PET) systems.

. Much recent attention on positron emission tomography (PET) is the development of time-of-flight (TOF) systems with ever-improving coincidence time resolution (CTR). This is because, when all other factors remain the same, a better CTR leads to images of better statistics and effectively increases the sensitivity of the system.

Image distortion by ambiguous multiple-photon detections in a superconducting nanowire single-photon imager and the correction method.

Scaling up superconducting nanowire single-photon detectors (SNSPDs) into a large array for imaging applications is the current pursuit. Although various readout architectures have been proposed, they cannot resolve multiple-photon detections (MPDs) currently, which limits the operation of the SNSPD arrays at high photon flux. In this study, we focused on the readout ambiguity of a superconducting nanowire single-photon imager applying time-of-flight multiplexing readout.

van der Waals Self-Epitaxial Growth of Inch-Sized Superconducting Niobium Diselenide Films.

Ultrathin superconducting films are the basis of superconductor devices. van der Waals (vdW) NbSe with noncentrosymmetry exhibits exotic superconductivity and shows promise in superconductor electronic devices. However, the growth of inch-scale NbSe films with layer regulation remains a challenge because vdW structural material growth is strongly dependent on the epitaxial guidance of the substrate.

Topotactic fabrication of transition metal dichalcogenide superconducting nanocircuits.

Superconducting nanocircuits, which are usually fabricated from superconductor films, are the core of superconducting electronic devices. While emerging transition-metal dichalcogenide superconductors (TMDSCs) with exotic properties show promise for exploiting new superconducting mechanisms and applications, their environmental instability leads to a substantial challenge for the nondestructive preparation of TMDSC nanocircuits. Here, we report a universal strategy to fabricate TMDSC nanopatterns via a topotactic conversion method using prepatterned metals as precursors.

Antireflection Coatings Based on PEDOT:PSS Conductive Polymer Using d-Sorbitol Additives for Terahertz Spectroscopy and Imaging.

Optical antireflection has been employed for a variety of applications in terahertz spectroscopy and detectors. However, current methods encounter challenges in terms of cost, bandwidth, structural complexity, and performance. In this study, a low-cost, broadband, and easily processed THz antireflection coating scheme based on the model of impedance-matching effect is proposed, using a 6 wt % d-sorbitol-doped poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (s-PEDOT:PSS) film.

Freestanding narrowband terahertz filters based on aluminum foil.

Terahertz (THz) filters with high transmission coefficient (T) in the passband and frequency selectivity are critical in numerous applications such as astronomical detection and next-generation wireless communication. Freestanding bandpass filters eliminate the Fabry-Pérot effect of substrate, thus providing a promising choice for cascaded THz metasurfaces. However, the freestanding bandpass filters (BPFs) using the traditional fabrication process are costly and fragile.

Modeling of a multireflector terahertz imaging system using a geometrical optics model based on angular spectrum theory.

We propose a simulation method for a multireflector terahertz imaging system. The description and verification of the method are based on an existing active bifocal terahertz imaging system at 0.22 THz.

Directional terahertz holography with thermally active Janus metasurface.

Dynamic manipulation of electromagnetic (EM) waves with multiple degrees of freedom plays an essential role in enhancing information processing. Currently, an enormous challenge is to realize directional terahertz (THz) holography. Recently, it was demonstrated that Janus metasurfaces could produce distinct responses to EM waves from two opposite incident directions, making multiplexed dynamic manipulation of THz waves possible.

Terahertz Spin Current Dynamics in Antiferromagnetic Hematite.

An important vision of modern magnetic research is to use antiferromagnets (AFMs) as controllable and active ultrafast components in spintronic devices. Hematite (α-Fe O ) is a promising model material in this respect because its pronounced Dzyaloshinskii-Moriya interaction leads to the coexistence of antiferromagnetism and weak ferromagnetism. Here, femtosecond laser pulses are used to drive terahertz (THz) spin currents from α-Fe O into an adjacent Pt layer.

Polarizer-free measurement of the full Stokes vector using a fiber-coupled superconducting nanowire single photon detector with a polarization extinction ratio of ∼2.

The characterization and manipulation of polarization state at single photon level are of great importance in research fields such as quantum information processing and quantum key distribution, where photons are normally delivered using single mode optical fibers. To date, the demonstrated polarimetry measurement techniques based on a superconducting nanowire single photon detector (SNSPD) require the SNSPD to be either highly sensitive or highly insensitive to the photon's polarization state, therefore placing an unavoidable challenge on the SNSPD's design and fabrication processes. In this article, we present the development of an alternative polarimetry measurement technique, of which the stringent requirement on the SNSPD's polarization sensitivity is removed.

Simple terahertz metasurface with broadband and efficient functionality.

Pancharatnam-Berry (PB) metasurfaces have demonstrated mighty capability to manipulate electromagnetic (EM) waves, and exhibited potential applications for devices with broadband and efficient functionality. However, it remains a challenge to simultaneously achieve broadband and efficient wavefront manipulation for terahertz (THz) components with simple profiles. Herein, we introduce a simple ultra-thin PB metasurface with superior properties in the THz region.

Fast and accurate measurement of the polarization-dependent detection efficiency of superconducting nanowire single photon detectors.

Superconducting nanowire single photon detectors (SNSPDs) have been extensively investigated due to their superior characteristics, including high system detection efficiency, low dark count rate and short recovery time. The polarization sensitivity introduced by the meandering-type superconductor nanowires is an intrinsic property of SNSPD, which is normally measured by sweeping hundreds of points on the Poincaré sphere to overcome the unknown birefringent problem of the SNSPD's delivery fiber. In this paper, we propose an alternative method to characterize the optical absorptance of SNSPDs, without sweeping hundreds of points on the Poincaré sphere.

Electrically addressable integrated intelligent terahertz metasurface.

Reconfigurable intelligent surfaces (RISs) play an essential role in various applications, such as next-generation communication, uncrewed vehicles, and vital sign recognizers. However, in the terahertz (THz) region, the development of RISs is limited because of lacking tunable phase shifters and low-cost sensors. Here, we developed an integrated self-adaptive metasurface (SAM) with THz wave detection and modulation capabilities based on the phase change material.