•LEND/LRO instrument neutron counting data sets have been analyzed to create high resolution maps of epithermal neutron flux at polar regions of the Moon.•The conversion from epithermal neutron flux ...to the H/H2O abundances is presented based on the simple subsurface models.•The polar lunar maps (poleward 70S/70N) of homogeneous hydrogen distribution are derived and discussed.
We present a method of conversion of the lunar neutron counting rate measured by the Lunar Reconnaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) instrument collimated neutron detectors, to water equivalent hydrogen (WEH) in the top ∼1m layer of lunar regolith. Polar maps of the Moon's inferred hydrogen abundance are presented and discussed.
We study and compare optical microcavities formed by GaN planar nanowires. Nanostructures with structural defects such as stacking faults and without defects are considered. The behavior of an ...exciton localized in a stacking fault is considered. Different behavior of the photoluminescence intensity and the photoluminescence decay time is observed for the cases under consideration. Theoretical calculations show the localization of the field at the ends of the structure.
The interaction of plasmonic whispering gallery modes on the surface of silver nanospheres with an exciton of the surrounding organic medium has been theoretically studied. DPAVBi ...(4,4'-bis4-(di-ptolylamino) styrylbiphenyl) was selected as an organic material due to its high oscillator strength. The results show that for spheres of sufficiently large radii, several plasmon modes can be localized on their surface at once, which makes them possible for strong coupling with an exciton. The calculated spectra confirm that plasmon modes can effectively interact with excitons in the surrounding organic material, which leads to a significant change in both the absorption and emission characteristics of the system. These observations highlight the potential of such hybrid systems for a number of applications in optoelectronics and photonics, making them a promising platform for further research in this area.
The description of Dynamic Albedo of Neutrons (DAN) experiment is presented, as a part of the NASA’s Mars Science Laboratory mission onboard the mars rover Curiosity. The instrument DAN includes ...Pulsing Neutron Generator (PNG) producing pulses of 14.1 MeV neutrons for irradiation of subsurface material below the rover, and Detectors and Electronics (DE) unit, which operates the instrument itself and measures the die-away time profiles of epithermal and thermal neutrons following each neutron pulse. It is shown that the DAN investigation will measure a content of hydrogen along the path of the MSL rover, and it will also provide information about a depth distribution of hydrogen at 10–20 regions selected for the detailed studies and sampling analysis.
Surface Emitting Quantum-Cascade Ring Laser Babichev, A. V.; Kolodeznyi, E. S.; Gladyshev, A. G. ...
Semiconductors (Woodbury, N.Y.),
07/2021, Letnik:
55, Številka:
7
Journal Article
Recenzirano
Quantum-cascade lasers with surface emission of radiation by means of a grating formed in the upper waveguide cladding layers by ion-beam milling are fabricated and studied. The active region of the ...laser heterostructure is based on the In
0.53
Ga
0.47
As/Al
0.48
In
0.52
As alloy alloys and uses a design with two-phonon resonance emptying of the lower level in the cascade. Room-temperature lasing near 7.9 μm is demonstrated for a laser with a ring-cavity diameter of 191 μm. The mode spacing in the lasing spectra corresponds to whispering-gallery modes.
The ion-beam etching of AlGaAs/GaAs heterostructures gives rise to radiation defects and, as a result, leads to photoluminescence quenching. Annealing at 620°C in an atmosphere of As almost ...completely restores the quantum efficiency of photoluminescence in the case of radiation-induced defects lying at a distance of up to 150 nm from the heterointerface.
An updated set of goals and objectives for the Mercury Gamma and Neutron Spectrometer (MGNS) are presented based on the most recent findings of the MESSENGER mission. The updated design of MGNS with ...the new CeBr
3
crystal for detection of gamma-ray along with its benefits for the detection of
40
K and K/Th ratio are discussed. MGNS will then be capable of measuring the elemental composition of shallow subsurface in order to empirically evaluate the fittest model on the origin of Mercury, as well as the presence of possible water ice deposits on the permanently shadowed polar craters on the planet. We present the results of the first measurements in space performed during the instrument commissioning phase and during the first Earth flyby which occurred in April 2020.
Light-emitting devices of modern photonics are based on the semiconductor structures containing layers with various physical parameters. To preserve initial parameters during focused ion beam (FIB) ...lithography, it is necessary to take into account the processes of radiation defect formation. Radiation-induced defects in target play role of nonradiative recombination centers leading to photoluminescence (PL) quenching. In our work, the FIB impact on the photoluminescence were examined using PL spectroscopy of milled Al
0.18
Ga
0.82
As/GaAs double heterostructure. In order to exclude photoexcited carriers losses in emitter layer, an experiment with subbarrier photoexcitation was organized. Finally, we compare our experimental findings with theoretical data proposed by stopping and range of ions in matter (SRIM) calculation.
We present an approach for the treatment of coupled-ridge lasers using focused ion beam (FIB) etching. We show experimentally that the FIB etching allows post-processing lateral mode tuning without ...deterioration of the main laser parameters.
The effect of ion energy in a focused ion beam in the range 12–30 keV on the formation depth of nonradiative recombination centers during etching of the Al
0
.
18
Ga
0
.
82
As/GaAs/Al
0
.
18
Ga
0
.
...82
As double heterostructure has been studied. It is shown that an increase in the ion energy leads to an increase in the concentration and propagation depth of radiation defects. It was found that during etching of focused ion beam with ion energies above 15 keV, the depth of formation of radiation defects exceeds 900 nm, which does not correspond to the calculations in the Stopping and Range of Ions in Matter.
