Ultra-Broad Linear Range and Sensitive Flexible Piezoresistive Sensor Using Reversed Lattice Structure for Wearable Electronics.

Flexible pressure sensors have attracted significant attention owing to their broad applicability in wearable electronics and human-machine interfaces. However, it is still challenging to simultaneously achieve a broad sensing range and high linearity. Here, we present a reversed lattice structure (RLS) piezoresistive sensor obtained through a layer-level engineered additive infill structure via conventional fused deposition modeling three-dimensional (3D) printing. The optimized RLS piezoresistive sensor attained a pressure sensing range (0.03-1630 kPa) with high linearity (coefficient of determination, R2 = 0.998) and sensitivity (1.26 kPa-1) due to the structurally enhanced compressibility and spontaneous transition of dominant sensing mechanism of the sensor. It also exhibited great mechanical/electrical durability and a rapid response/recovery time (170/70 ms). This remarkable performance enables the detection of various human motions over a broad spectrum, from pulse detection to human walking. Finally, a wearable electronic glove was developed to analyze the pressure distribution in various situations, thereby demonstrating its applicability in multipurpose wearable electronics.

All-optical frequency-dependent magnetic switching in metal-insulator-metal stub structures.

Many attempts to switch magnetization with optical pulses were based on free-space coupling schemes of circularly polarized light pulses, so-called all-optical helicity-dependent magnetic switching; however, waveguide coupling schemes are promising for on-chip all-optical magnetic switching. Metal-insulator-metal (MIM) stub structures provide a promising platform for highly integrated photonic circuits, thanks to their compact size, on-chip compatibility, and ease of fabrication. We found clockwise and counterclockwise ring-like modes in the MIM stub structure, which can act as effective magnetic fields with two opposite directions due to the inverse Faraday effect. Effective magnetic field spectra inside the MIM stub have dual resonant peaks at which the effective magnetic field intensity reaches its extreme values with opposite signs, corresponding to binary magnetic states. Switching between the binary magnetic states can be achieved by altering the optical pump frequency. The all-optical frequency-dependent magnetic switching in the MIM stub may provide a chip-compatible and ultracompact tool for ultrafast switching of magnetic order.

Switchable plasmonic routers controlled by external magnetic fields by using magneto-plasmonic waveguides.

We analytically and numerically investigate magneto-plasmons in metal films surrounded by a ferromagnetic dielectric. In such waveguide using a metal film with a thickness exceeding the Skin depth, an external magnetic field in the transverse direction can induce a significant spatial asymmetry of mode distribution. Superposition of the odd and the even asymmetric modes over a distance leads to a concentration of the energy on one interface which is switched to the other interface by the magnetic field reversal. The requested magnitude of magnetization is exponentially reduced with the increase of the metal film thickness. Based on this phenomenon, we propose a waveguide-integrated magnetically controlled switchable plasmonic routers with 99-%-high contrast within the optical bandwidth of tens of THz. This configuration can also operate as a magneto-plasmonic modulator.

Actively phase-controlled coupling between plasmonic waveguides via in-between gain-assisted nanoresonator: nanoscale optical logic gates.

The development of nanoscale optical logic gates has attracted immense attention due to increasing demand for ultrahigh-speed and energy-efficient optical computing and data processing, however, suffers from the difficulty in precise control of phase difference of the two optical signals. We propose a novel conception of nanoscale optical logic gates based on actively phase-controlled coupling between two plasmonic waveguides via an in-between gain-assisted nanoresonator. Precise control of phase difference between the two plasmonic signals can be performed by manipulating pumping rate at an appropriate frequency detuning, enabling a high contrast between the output logic states "1" and "0." Without modification of the structural parameters, different logic functions can be provided. This active nanoscale optical logic device is expected to be quite energy-efficient with ideally low energy consumption on the order of 0.1 fJ/bit. Analytical calculations and numerical experiments demonstrate the validity of the proposed concept.