Long-wavelength Radiation Research Articles

Generation of spin-motion entanglement in a trapped ion using long-wavelength radiation

Applying a magnetic field gradient to a trapped ion allows long-wavelength microwave radiation to produce a mechanical force on the ion's motion when internal transitions are driven. We demonstrate such a coupling using a single trapped \Yb{171}~ion, and use it to produce entanglement between the spin and motional state, an essential step towards using such a field gradient to implement multi-qubit operations.

Effect of Sequential Exposition to Short- and Long-Wavelength Radiation on the Optical Absorption in the Bismuth Titanium Oxide Crystal Doped by Aluminum

Changes in the spectral dependences of the optical absorption induced in the bismuth titanium oxide crystal doped by aluminum as a result of sequential exposition to cw laser radiation first with the wavelength λi = 532nm and then with the longer wavelength λn = 633, 655, 663, 780, 871, or 1064nm are investigated. Our experiments show that after the short-wavelength exposition to radiation with λi = 532nm, the optical absorption in the crystal increases, and in the range 470–1000nm, yields the spectrum whose form is independent of the initial crystal state. The subsequent exposition to longer-wavelength radiation leads to enhanced transmittance of the crystal in the examined spectral range. A maximum decrease of the optical absorption in the crystal is observed upon exposure to radiation with the wavelength λn = 663nm.

Upconversion nanoparticles: a versatile solution to multiscale biological imaging.

Lanthanide-doped photon upconverting nanomaterials are emerging as a new class of imaging contrast agents, providing numerous unprecedented possibilities in the realm of biomedical imaging. Because of their ability to convert long-wavelength near-infrared excitation radiation into shorter-wavelength emissions, these nanomaterials are able to produce assets of low imaging background, large anti-Stokes shift, as well as high optical penetration depth of light for deep tissue optical imaging or light-activated drug release and therapy. The aim of this review is to line up some issues associated with conventional fluorescent probes, and to address the recent advances of upconverting nanoparticles (UCNPs) as a solution to multiscale biological imaging applications.

High efficiency structured EUV multilayer mirror for spectral filtering of long wavelengths.

High spectral purity at longer wavelength side is demanded in many extreme ultraviolet (EUV) and soft X-ray (together also referred to as XUV) optical systems. It is usually obtained at the expense of a high loss of XUV efficiency. We proposed and developed a new method based on a periodic, tapered structure integrated with an EUV multilayer. The longer wavelength radiation is scattered/diffracted away by the tapered multilayer structure while the EUV light is reflected. The first proof-of-principle showed a broadband suppression from λ = 100-400 nm with an average factor of 14. Moreover, a high EUV reflectance of 64.7% was achieved, which corresponds to 94% of the efficiency of a regular EUV multilayer mirror.

Terahertz Optical Conductance of n-type Monolayer MoS2

We present a theoretical study on optoelectronic properties of n-type monolayer MoS2 under long-wavelength light radiation. The optical conductance for such material system is evaluated using the energy-balance equation derived from the Boltzmann equation in the presence of linearly polarized radiation field. For n-type monolayer MoS2, the optical absorption in terahertz bandwidth can be achieved via intra spin-conserved transitions and inter spin-flip transitions at K and K′ valleys. More importantly, we find that there is a terahertz absorption peak in the radiation frequency range 2–10 THz. The intensity and width of this absorption peak depend sensitively on temperature and the position of the peak can be tuned via changing the electron density. This study shows that n-type monolayer MoS2 can be applied as frequency tunable THz optical and optoelectrical devices.

Tiny warming of residual anthropogenicCO2

The residual fraction of anthropogenic CO2emissions which has not been captured by carbon sinks and remains in the atmosphere, is estimated by two independent experimental methods which support each other: the13C /12C ratio and the temperature-independent fraction of d( CO2)/dt on a yearly scale after subtraction of annual fluctuations the amplitude ratio of which reaches a factor as large as 7. The anthropogenic fraction is then used to evaluate the additional warming by analysis of its spectral contribution to the outgoing long-wavelength radiation (OLR) measured by infrared spectrometers embarked in satellites looking down. The anthropogenic CO2additional warming extrapolated in 2100 is found lower than 0.1°C in the absence of feedbacks. The global temperature data are fitted with an oscillation of period 60 years added to a linear contribution. The data which support the 60-year cycle are summarized, in particular sea surface temperatures and sea level rise measured either by tide gauge or by satellite altimetry. The tiny anthropogenic warming appears consistent with the absence of any detectable change of slope of the 130-year-long linear contribution to the temperature data before and after the onset of large CO2emissions.

UV spectral filtering by surface structured multilayer mirrors

A surface structured extreme ultraviolet multilayer mirror was developed showing full band suppression of UV (λ=100-400 nm) and simultaneously a high reflectance of EUV light (λ=13.5 nm). The surface structure consists of Si pyramids, which are substantially transparent for EUV but reflective for UV light. The reflected UV is filtered out by blazed diffraction, interference, and absorption. A first demonstration pyramid structure was fabricated on a multilayer by using a straightforward deposition technique. It shows an average suppression of 14 times over the whole UV range and an EUV reflectance of 56.2% at 13.5 nm. This robust scheme can be used as a spectral purity solution for all XUV sources that emit longer wavelength radiation as well.

Grating-coupled mid-infrared light emission from tensilely strained germanium nanomembranes

Mechanically stressed nanomembranes are used to demonstrate mid-infrared interband light emission from Ge within the 2.1–2.5 μm atmospheric transmission window. Large biaxial tensile strain is introduced in these samples to convert Ge into a (near-) direct-bandgap semiconductor and to red-shift its luminescence. A diffractive array of Ge pillars is used to outcouple the long-wavelength interband radiation, which is otherwise primarily emitted in the sample plane. An order-of-magnitude strain-induced enhancement in radiative efficiency is also reported, together with the observation of luminescence signatures associated with photonic-crystal cavity modes. These results are promising for the development of silicon-compatible lasers for mid-infrared optoelectronics applications.

Infrared diffractive filtering for extreme ultraviolet multilayer Bragg reflectors

We report on the development of a hybrid mirror realized by integrating an EUV-reflecting multilayer coating with a lamellar grating substrate. This hybrid mirror acts as an efficient Bragg reflector for extreme ultraviolet (EUV) radiation at a given wavelength while simultaneously providing spectral-selective suppression of the specular reflectance for unwanted longer-wavelength radiation due to the grating phase-shift resonance. The test structures, designed to suppress infrared (IR) radiation, were fabricated by masked deposition of a Si grating substrate followed by coating of the grating with a Mo/Si multilayer. To give the proof of principle, we developed such a hybrid mirror for the specific case of reflecting 13.5 nm radiation while suppressing 10 μm light, resulting in 61% reflectance at the wavelength of 13.5 nm together with the 70 × suppression rate of the specular reflection at the wavelength of 10 μm, but the considered filtering principle can be used for a variety of applications that are based on utilization of broadband radiation sources.

Tunneling-induced high-efficiency four-wave mixing in asymmetric quantum wells

An asymmetric double quantum wells (QWs) structure with resonant tunneling is suggested to achieve high efficient four wave mixing (FWM). We analytically demonstrate that the resonant tunneling can induce high efficient mixing wave in such a semiconductor structure with a low light pump wave. In particular, the FWM conversion efficiency can be enhanced dramatically in the vicinity of the center frequency. This interesting scheme may be used to generate coherent long-wavelength radiation in solid-state system.

Energy transfer from Bi3+ to Eu3+ triggers exceptional long-wavelength excitation band in ZnWO4:Bi3+, Eu3+ phosphors

Color-tunable phosphors of ZnWO4:x mol% Bi3+, 3 mol% Eu3+ (x = 0.5, 1, 2, 3, 4, 5) were prepared through a precipitation method and their luminescence properties were investigated as a function of Bi3+ concentration. The most intense 616 nm emission indicates that Eu3+ occupies the Zn2+ sites without inversion symmetry. The spectral overlap between the emission band of Bi3+ and the excitation band of Eu3+ supports the energy transfer from Bi3+ to Eu3+, which has been demonstrated to be of a resonant type via a dipole–dipole mechanism. Energy transfer from Bi3+ to Eu3+ triggers a long-wavelength excitation band at 340 nm originating from the Bi3+ 1S0 → 3P1 transition, which makes the phosphors fit for long-wavelength radiation. The decay curves of Bi3+ and Eu3+ emission were measured to understand the energy transfer processes. Interestingly, the critical concentration of Bi3+ for Eu3+ 616 nm emission in ZnWO4:Bi3+, Eu3+ was greatly increased by 400 times compared with that for Bi3+ 560 nm emission in ZnWO4:Bi3+. Color-tunable emission in ZnWO4:Bi3+, Eu3+ phosphors can be obtained by the modulation of the excitation wavelength and the ratio of Bi3+ and Eu3+. Our work provides a novel approach to develop phosphors which can be excited effectively under long-wavelength radiation.

Photodegradation and inhibition of drug-resistant influenza virus neuraminidase using anthraquinone–sialic acid hybrids

The anthraquinone-sialic acid hybrids designed effectively degraded not only non-drug-resistant neuraminidase but also drug-resistant neuraminidase, which is an important target of anti-influenza therapy. Degradation was achieved using long-wavelength UV radiation in the absence of any additives and under neutral conditions. Moreover, the hybrids efficiently inhibited neuraminidase activities upon photo-irradiation.

STEP Wastewater Treatment: A Solar Thermal Electrochemical Process for Pollutant Oxidation

A solar thermal electrochemical production (STEP) pathway was established to utilize solar energy to drive useful chemical processes. In this paper, we use experimental chemistry for efficient STEP wastewater treatment, and suggest a theory based on the decreasing stability of organic pollutants (hydrocarbon oxidation potentials) with increasing temperature. Exemplified by the solar thermal electrochemical oxidation of phenol, the fundamental model and experimental system components of this process outline a general method for the oxidation of environmentally stable organic pollutants into carbon dioxide, which is easily removed. Using thermodynamic calculations we show a sharply decreasing phenol oxidation potential with increasing temperature. The experimental results demonstrate that this increased temperature can be supplied by solar thermal heating. In combination this drives electrochemical phenol removal with enhanced oxidation efficiency through (i) a thermodynamically driven decrease in the energy needed to fuel the process and (ii) improved kinetics to sustain high rates of phenol oxidation at low electrochemical overpotential. The STEP wastewater treatment process is synergistic in that it is performed with higher efficiency than either electrochemical or photovoltaic conversion process acting alone. STEP is a green, efficient, safe, and sustainable process for organic wastewater treatment driven solely by solar energy.

Bêhounekite, U(SO4)2(H2O)4, from Jáchymov (St Joachimsthal), Czech Republic: the first natural U4+sulphate

AbstractBêhounekite, orthorhombic U(SO4)2(H2O)4, is the first natural sulphate of U4+. It was found in the Geschieber vein, Jáchymov (St Joachimsthal) ore district, Western Bohemia, Czech Republic, crystallized on the altered surface of arsenic and associated with kaatialaite, arsenolite, claudetite, unnamed phase UM1997-20-AsO:HU and gypsum. Bêhounekite most commonly forms short-prismatic to tabular green crystals, rarely up to 0.5 mm long. The crystals have a strong vitreous lustre and a grey to greenish grey streak. They are brittle with an uneven fracture and have very good cleavage along ﹛100﹜. The Mohs hardness is about 2. The mineral is not fluorescent either in short- or long-wavelength UV radiation. Bêhounekite is moderately pleochroic, α∼β is pale emerald green and γ is emerald green, and is optically biaxial (+) withα =1.590(2), β = 1.618(4), γ = 1.659(2) (590 nm), 2V (calc.) = 81°, birefringence 0.069. The empirical formula of bêhounekite (based on 12 O atoms, from an average of five point analyses) is (U0.99Y0.03)Σ1.02(SO4)1.97(H2O)4. The simplified formula is U(SO4)2(H2O)4, which requires UO253.77. SO331.88, H2O 14.35, total 100.00 wt.%. Bêhounekite is orthorhombic, space groupPnma, a =14.6464(3),b =11.0786(3), c = 5.6910(14) Å,V =923.43(4) Å3,Z =4, Dcalc= 3.62 g cm–3. The seven strongest diffraction peaks in the X-ray powder diffraction pattern are[dobsin Å (I)(hid)]:7.330 (100) (200), 6.112 (54) (210), 5.538 (21) (020), 4.787 (42) (111), 3.663 (17) (400), 3.478 (20) (410), 3.080 (41) (321). The crystal structure of bêhounekite has been solved by the charge-flipping method from single-crystal X-ray diffraction data and refined toR1=2.10 % with aGOF =1.51, based on 912 unique observed diffractions. The crystal structure consists of layers built up from [8]-coordinate uranium atoms and sulphate tetrahedra. The eight ligands include four oxygen atoms from the sulphate groups and four oxygen atoms from the H2O molecules. Each uranium coordination polyhedron is connected via sulphate tetrahedra with other uranium polyhedra and through hydrogen bonds to the apices of sulphate tetrahedra. The dominant features of the Raman and infrared spectra of bêhounekite are related to stretching vibrations of SO4tetrahedra (∼1200–950 cm–1), O-H stretching modes (∼3400–3000 cm–1) and H—O—H bending modes (∼1650 cm–1). The mineral is named in honour of František Bêhounek, a well known Czech nuclear physicist.

Determination of Lithium in Mineral Water Samples by X-Ray Fluorescence Spectrometry

A method is shown for the determination of trace amounts of lithium by X-ray fluorescence spectrometry (XRF) in natural mineral waters with various therapeutic effects originating in Poland. The method is an expansion of X-ray fluorescence spectrometry applications to the determination of a very light element. The direct determination of lithium by XRF is practically impossible due to the extremely low fluorescence yield and long-wavelength characteristic radiation of such a light element. The lithium is determined via iron after precipitation with stoichiometric potassium lithium periodatoferrate(III) complex. The solution obtained after dissolving the complex was pipetted onto Mylar foil for XRF analysis. As little as 1 μg Li may be determined with this method. Accurate lithium determinations can be obtained using simple calibration samples requiring only pipetting Fe solution in the range 8.0-28.0 μg onto the Mylar foil. The prepared samples are thin, which allows the errors resulting from self-absorption or matrix effects to be neglected. Our studies give essential information about the quality of the analyzed waters.

Characterization of nano-structured surfaces by EUV scatterometry

Scatterometry in the UV and the VIS is widely used for the inspection of nano-structured surfaces in, e.g. quantitative wafer metrology in the semiconductor industry. As the structures become progressively smaller, ever fewer propagating diffraction orders exist. Consequently, these few orders do not carry enough information about the structure any more. Particularly the reconstruction of structures without detailed a priori knowledge becomes impossible due to this lack of information. The Physikalisch-Technische Bundesanstalt (PTB) has developed extreme UV (EUV) scatterometry using its EUV reflectometry facility at the electron storage ring BESSY II. The short wavelength of EUV at around 13 nm is advantageous since it provides more propagating diffraction orders compared to the longer wavelength radiation. The short wavelength also increases the sensitivity to small structural features, particularly roughness. We present the application of EUV scatterometry for the characterization of absorber lines with a trapezoidal cross section on semiconductor photo masks and for the characterization of ultra-smooth surfaces of EUV multilayer mirrors. It is shown that structure roughness significantly impacts the scattered diffraction intensities from structured surfaces and must be included in the structure reconstruction algorithms using inverse modelling by FEM. Estimates for the changes in reconstructed geometrical parameters induced by roughness are presented.

Optical Cherenkov radiation in ultrafast cascaded second-harmonic generation

We show through theory and numerics that when few-cycle femtosecond solitons are generated through cascaded (phase-mismatched) second-harmonic generation, these broadband solitons can emit optical Cherenkov radiation in the form of linear dispersive waves located in the red part of the spectrum. The beating between the dispersive wave and the soliton generates trailing temporal oscillations on the compressed soliton. Insertion of a simple short-wave pass filter after the crystal can restore a clean soliton. On the other hand, bandpass filtering around the dispersive wave peak results in near-transform-limited ultrashort mid-IR pulses with pulse durations much shorter than the input near-IR pulse. The Cherenkov radiation for the crystal considered ($\ensuremath{\beta}$-barium borate) is found for pump wavelengths in the range $\ensuremath{\lambda}=0.95--1.45 \mathrm{\ensuremath{\mu}}\mathrm{m}$, and is located in the regime $\ensuremath{\lambda}=1.5--3.5 \mathrm{\ensuremath{\mu}}\mathrm{m}$. For shorter pump wavelengths, the phase-matching point is located in the absorption region of the crystal, effectively absorbing the generated dispersive wave. By calculating the phase-matching curves for typically used frequency conversion crystals, we point out that the mid-IR absorption in the crystal in many cases automatically will filter away the dispersive wave. Finally, an investigation of recent experimental results uncovers a four-wave-mixing phenomenon related to Cherenkov radiation that is an additional generation mechanism of long-wavelength radiation that can occur during soliton compression. We discuss the conditions that lead to this alternative dynamics rather than generation of Cherenkov radiation.

Photodegradation of Target Oligosaccharides by Light‐Activated Small Molecules

Shine on, shine on: The designed anthraquinone/boronic acid hybrid 1 selectively caused the degradation of oligosaccharides that have a β-D-galactofuranoside residue, which is a unique component in mycobacterial cell walls. Degradation was achieved using long-wavelength UV radiation in the absence of any additives and under neutral conditions.

Characteristic features of generation of few-cycle pulses in infrared and terahertz spectral ranges upon interaction of two femtosecond pulses of different frequencies in air

The results of a theoretical analysis of the generation of broadband radiation in the infrared and terahertz spectral ranges upon the excitation of plasma in air by two femtosecond pulses at the fundamental and second-harmonic frequencies of a Ti-sapphire laser are presented. It is found that the appearance of long-wavelength radiation in a strong field of pulses of different frequencies can be described in terms of strongly anharmonic oscillations of optical electrons, whereby electrons are pulled far away from their atoms; these oscillations are accompanied by cascade transitions of electrons from their ground state to a bound excited state, followed by a transition to the continuum. It is shown that the generated infrared and terahertz radiation appears in the form of pulses containing a few oscillations of the light field. The efficiency of terahertz generation varies periodically with an increase in the interaction length of the femtosecond pulses of different frequencies.

Red sky at night: Long-wavelength photochemistry in the atmosphere

Atmospheric chemistry proceeds with a significant number of mechanisms involving radicals. At high altitudes, the photolyzing irradiance of UV explains the encountered concentrations. However the formation of OH, especially at lower altitudes, occurs under conditions where standard atmospheric photochemistry models underpredict observed concentrations. Yet when exploring the molecular dynamics, long-wavelength solar radiation (red and near-IR) can explain the prevalence of these reactions. Donaldson et al. review the photochemistry and discuss the implications for air pollution and atmospheric chemistry/climate.