Solar cells and optical detection devices often incorporate antireflective surfaces to reduce undesired reflection enhance absorption. This letter reports a “black silicon” structure of porous silicon fabricated by using electrochemical etching. The sample has gradient-index multilayer structure, i.e., the refraction indices increase from top (near air) bottom Si substrate). Reflectance below 5% is obtained over broad wave number range (3000–28000cm−1) depression mechanism reflectance...

Chiral structure can be applied to construct metamaterial with negative refractive index (NRI). In an assembly of double-layered metallic U-shaped resonators two resonant frequencies wH and wL, the effective induced electric magnetic dipoles, which are contributed by specific surface current distributions, collinear at same frequency. Consequently, for left circularly polarized light, NRI occurs wH, whereas right light it wL. Our design provides a new example apply chiral structures tune...

Abstract We proposed a new strategy for utilizing rare‐earth–free‐activated self‐referencing optical material with dual activators temperature sensing, which was synthesized by conventional high‐temperature solid‐state method and scarcely reported. Originating from the different thermal responses of Mn 4+ Bi 3+ ions, /Bi ‐based dual‐emitting fluorescence intensity ratio (FIR) as dual‐modal signal sensing has been corroborated promising method. Due to outstanding resistance activator...

To detect the smallest delay faults at a fault site, longest path(s) through it must be tested full speed. Existing test generation tools are inefficient in automatically identifying testable paths due to high computational complexity. In this work methodology for scan-based synchronous sequential circuits is presented, under two at-speed strategies used industry. The compared and efficiency evaluated on ISCAS89 benchmark industrial designs. Experiments show that testing transition can done...

Fourier transform infrared (FTIR) spectrometer is a powerful tool for studying the photoluminescence (PL) properties of semiconductors, due to its well-known multiplexing and throughput advantages. However, it suffers from internal He–Ne laser disturbance in near-infrared and∕or environmental background thermal emission mid- far-infrared spectral regions. In this work, modulated PL technique developed based on step-scan (SS)-FTIR spectrometer. Theoretical analysis conducted, applications are...

We report in this Letter that when radiation is incident on a metal surface perforated with an array of ring-shaped subwavelength apertures, the phase difference between propagating Bloch wave and localized can be tailored by geometrical parameters so as to affect shape transmission spectrum. Above resonant frequency aperture, interference two kinds waves leads minimum spectrum, whereas below it, maximum. suggest feature provides flexibility engineering surface-wave-based all-optical devices.

The oxygen spectrometer for atmospheric science on a balloon (OSAS-B) is the first 4.7-THz heterodyne stratospheric balloon. It has been developed remote sensing of emission neutral atomic in mesosphere and lower thermosphere Earth. OSAS-B comprises receiver based hot-electron bolometer mixer quantum-cascade laser as local oscillator. high sensitivity superconducting detector large resolving power approximately 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML"...

The application of terahertz (THz) radiation in scientific research as well applied and commercial technology has expanded rapidly recent years. One example is the progress high-resolution THz spectroscopy based on quantum cascade lasers, which enabled new observations astronomy, atmospheric research, plasma diagnostics. However, lack easy-to-use miniaturised detectors hampered development compact systems out laboratory environment. In this paper, we introduce a high-speed pyroelectric...

Rare-earth (RE) doping has been demonstrated as a feasible approach to improve the cyclic performance of Ni-Mn-based Heusler alloys, but current demonstration underlying mechanism is simply ascribed strengthening grain boundary cohesion. In this work, effects brought by RE on microstructure, stress induced martensitic transformation behavior and stability alloys were systematically investigated. By Tb doping, stable adiabatic temperature change (|ΔTad|) ∼ 5.5 K over 1000 cycles with no...

We report on the observation of an approximately linear reduction in maximum operating temperature with increasing emission frequency for terahertz quantum-cascade lasers between 4.2 and 5.4 THz. These are based same design type, but vary period length barrier height cascade structure. The sample emitting at highest around THz can be operated pulsed mode up to 56 K. identify additional relaxation channel electrons by longitudinal optical phonon scattering from upper lower laser level losses...

A model for lattice thermal conductivity in a semiconductor nanowire with rectangular cross section is investigated. It based on solving the equations of phonon radiative transfer taking into account interface scattering and modification acoustic dispersion. From numerical calculations, we predict decrease by an order magnitude 10-nm-thick 20-nm-wide nanowire. The confinement play important roles reduction conductivity. found to increasing temperature at moderate high temperatures. shown...

Local oscillators in terahertz heterodyne spectrometers have to be operated continuous-wave mode at precisely defined target frequencies. In particular, for advanced airborne instruments, several specifications such as operating temperature and cooling requirements are necessary considered. We developed a quantum-cascade laser (QCL) applicable local oscillator spectroscopy of the OI line 4.745 THz, which is particular interest astronomy. demonstrate distributed-feedback QCL up about 60 K,...

We have realized GaAs/AlAs quantum-cascade lasers operating at 4.75 THz exhibiting more than three times higher wall plug efficiencies GaAs/Al0.25Ga0.75As with an almost identical design. At the same time, threshold current density 10 K is reduced from about 350 A/cm2 for laser to 120 laser. Substituting AlAs Al0.25Ga0.75As barriers leads a larger energy separation between subbands reducing probability leakage currents through parasitic states and reabsorption of light. The allow shift...

Abstract We report on terahertz (THz) quantum-cascade lasers (QCLs) based GaAs/AlAs heterostructures, which exhibit single-mode emission at 3.360, 3.921, and 4.745 THz. These frequencies are in close correspondence to fine-structure transitions of Al atoms, N + ions, O respectively. Due the low electrical pump power these THz QCLs, they can be operated a mechanical cryocooler continuous-wave mode, while sufficient intrinsic tuning range more than 5 GHz is maintained. The operation QCLs allow...

Abstract This paper describes the first implementation of terahertz (THz) quantum cascade lasers for high-resolution absorption spectroscopy on plasmas. Absolute densities ground state atomic oxygen were directly obtained by using fine structure transition at approximately 4.75 THz. Measurements performed a low-pressure capacitively coupled radio frequency discharge. The detection limit in this arrangement was found to be <?CDATA $2 \times 10^{13}$?> <mml:math...

In Czochralski (CZ)-Si, crystal originated particles (COPs) and bulk micro-defects (BMDs), which are primarily composed of voids O-precipitates (OPs), respectively, have profound influences on the properties wafers and...

The rising prevalence of orthopedic conditions, driven by an aging population, has led to a growing demand for advanced implant materials. Traditional metals such as stainless steel and titanium alloys are biologically inert often necessitate secondary surgical removal, imposing both economic psychological burdens on patients. Biodegradable zinc-based offer promising alternatives due their moderate degradation rates, biocompatibility, tissue-healing properties. However, existing studies...