Ce:LaB3O6 glass for high-resolution radiation dosimetry

Ce:LaB3O6 (LBO) glass, whose constituents are abundant elements and fabrication is easy and cheap, is found to be a promising thermoluminescence (TL) dosimeter. This is originally achieved by CeF3 doping and melting under a reducing atmosphere, with the optimum concentration of 0.1% (quantum efficiency = 66%). The corresponding Ce interatomic distance is ~ 4 nm, below which concentration quenching occurs via Ce dipole-dipole interaction, as elucidated experimentally by Dexter’s theory. Ce:LBO exhibits a good dose resolution, with a linear dependence covering five orders of magnitude on both irradiation-dose and TL-response. Furthermore, it can be cyclically irradiated and read without degradation.

Direct observation of three-dimensional transient temperature distribution in SiC Schottky barrier diode under operation by optical-interference contactless thermometry (OICT) imaging

We have developed optical-interference contactless thermometry (OICT) imaging technique to visualize three-dimensional transient temperature distribution in 4H-SiC Schottky barrier diode (SBD) under operation. When a 1 ms forward pulse bias was applied, clear variation of optical interference fringes induced by self-heating and cooling were observed. Thermal diffusion and optical analysis revealed three-dimensional temperature distribution with high spatial (≤ 10 μm) and temporal (≤ 100 μs) resolutions. A hot spot that signals breakdown of the SBD was successfully captured as an anormal interference, which indicated a local heating to a temperature as high as 805 K at the time of failure.

Nanosecond-scale all-optical Ti3C2Tx-MXene modulator

Inspired by recent advancements of graphene-based ultrafast photonic devices, as a graphene-like two-dimensional layer-structure material, Ti3C2Tx-MXene has gained much interest in nonlinear optical applications, especially in all-optical intensity modulation. Herein, we successfully fabricated an all-optical modulator based on Ti3C2Tx-Mxene/polyvinyl-alcohol film with nanosecond-scale response time, modulation speed of 100 kHz, and modulation depth of 10%. Furthermore, the variation of fall edges of modulated signal pulse attributing to thermo-optic effect under different pump power was also observed. Considering the ease of fabrication, low cost, ease integration, the proposed novel modulator may open the door for highspeed all-optical communications and signal processing.

An engineering model for high-speed switching in GeSbTe phase-change memory

Ge2Sb2Te5 is the most successful phase-change alloy in non-volatile memory using the amorphous-crystal phase transition. In deriving further high performance in switching, especially SET speed (from amorphous to crystal transition) should still be modified. In this work, It was examined an ideal Ge2Sb2Te5 alloy based on the Kolobov model using ab-initio molecular dynamics simulations. As a result, it was cleared that a uniaxial exchange between vacancies and Ge atoms is the crucial role in realizing high-speed switching and a large contrast in the resonance bonding state in the alloy. The vacancy engineering enables the alloy switching speed extremely faster.

Continuous-flow synthesis of ultrahigh luminescent perovskite nanocrystals using forced thin film reactor and application for light-emitting diodes

Owing to their excellent optical properties, organolead halide perovskite nanocrystals (PeNCs) have gained significant attention. Considering their industrial contribution, exploring practical production of high-quality PeNCs is of major importance. In this work, we demonstrate continuous-flow synthesis of ultrahigh luminescent PeNCs with high color purity using a forced thin film reactor. We successfully demonstrate the effectiveness of this reactor as a crystal growth environment. The photoluminescence quantum yields were improved to 94% as a result of the unique mixing process. After film formation, this reactor enabled the application for perovskite light-emitting diodes.

Brillouin gain spectrum manipulation using multifrequency pump and probe for slope-assisted BOTDA with wider dynamic range

We propose slope assisted Brillouin optical time domain analysis (SA-BOTDA) with virtual Brillouin gain spectrum (BGS) generated by multifrequency pump and probe. The virtual BGS having a wide linear slope region of 100 MHz is easily generated by employing time-to-space spectral shaping technique that has been originally developed for generating short optical pulses. We demonstrate the distribution of virtual BGS realized by using five spectral components of pump and probe.

Revealing the Quadrupole Radiation of Liquid Gallium Nanospheres

Gallium (Ga) nanospheres (NSs) with diameters ranging from 50 to 300 nm are fabricated by using femtosecond laser ablation. The forward scattering of large Ga nanospheres measured using dark-field microscopy is determined by the coherent interaction between dipole and quadrupole resonances while it becomes governed by the dipole resonance when evanescent wave excitation is employed. We demonstrate that the scattering spectrum and pattern of quadrupole of large Ga NS can be resolved by using a cross-polarized analyzer in the collection channel. The experimental observations agree well with the numerical simulation based on the complex refractive index of liquid Ga.

An ultrathin acoustic metasurface composed of an anisotropic three-component resonator

An ultrathin acoustic metasurface consisting of an anisotropic three-component resonator is proposed. The resonator can induce nondegenerate dipole resonances at the same resonant frequencies. A large phase delay can be obtained based on the resonance, which can be modulated by the direction of polarization. The anisotropic resonator can be regarded as an effective homogenous medium with an anisotropic mass density, and the phase change can also be attributed to the change of the effective material parameters. A good comparison between the results for the metasurface and its effective slab is obtained.

Enhancing excitons by oleic acid treatment in WS2, MoS2, and WS2/MoS2 heterostructure

The neutral and interlayer exciton originates from intralayer and interlayer coupling, respectively. Unlike neutral exciton, the interlayer excitons at room temperature are hard to observe and manipulate due to instability. In this work, we show the photoluminescence of WS$_2$ and MoS$_2$ neutral exciton can be improved by oleic acid passivation, allowing trion peaks to be observed at room temperature. More importantly, a 3-fold increase in peak intensity of interlayer excitons is achieved, and the energy peak is blue-shifted 107 meV. Our work paves the way to investigate excitons in two-dimensional transition metal dichalcogenides monolayers and heterostructures at room temperature.

Terahertz-wave detector on silicon carbide platform

We developed a novel terahertz-wave detector fabricated on a SiC platform implementing an InP/InGaAs Fermi-level managed barrier (FMB) diode. The FMB diode epi-layers were transferred on a SiC substrate, and a waveguide coupler and filters were monolithically integrated with an FMB diode. Then, fabricated detector chip was assembled in a fundamental mixer module with a WR-3 rectangular-waveguide input port. It exhibited a minimum noise equivalent power as low as 3e-19 W/Hz at around 300 GHz for a local oscillator power of only 30 microwatts.