Pulsed Inductive Laser on Krypton Neutral Atoms Transitions in the IR Spectral Range

Generation of a coherent electromagnetic radiation in the far IR (THz) spectral range upon excitation of a semiconductor InAs crystal by 70-fs Ti: sapphire laser pulses is studied. The effect of a magnetic field of different orientation on generation in the submillimeter-wavelength range is analyzed. Placing the crystal into the magnetic field of an optimized permanent magnet with a strength of 5 kOe aligned along the surface of the semiconductor increased the power of generated radiation by a factor of six compared with that in the absence of the field. For the average pump-laser output power of 150 mW and repetition rate of 80 MHz, the average power of the THz radiation reached 100 nW. For detection of ultrashort pulses of the THz radiation, we used, for the first time, a highly sensitive uncooled optoacoustic detector, which detected signals with a power lower than 1 nW.

The effect of treatments in plasmas of different gases and subsequent deposition of diamond-like carbon films (DCFs) on the transmission of semi-insulating GaAs crystals in the IR spectral range has been analyzed. It is shown that deposition of 1- to 1.5-μm DCFs makes it possible to increase the GaAs transmission in the range of 4–15 μm and that preliminary treatment in H+ or Ar+ plasma increases the optical transmission of the DCF-GaAs structure. A mechanism is proposed to explain the effect of plasma treatment on the optical transmission of semi-insulating GaAs in the IR spectral range.

Defect transformations in nitrogen-doped CVD diamond during irradiation and annealing

The cumulative retardance Delta(t) introduced between the p and the s orthogonal linear polarizations after two successive total internal reflections (TIRs) inside a right-angle prism at complementary angles phi and 90 degrees - phi is calculated as a function of phi and prism refractive index n. Quarter-wave retardation (QWR) is obtained on retroreflection with minimum angular sensitivity when n=(sqr rt 2+1)(1/2)=1.55377 and phi =45 degrees. A QWR prism made of N-BAK4 Schott glass (n=1.55377 at lambda=1303.5 nm) has good spectral response (<5 degrees retardance error) over the 0.5-2 microm visible and near-IR spectral range. A ZnS-coated right-angle Si prism achieves QWR with an error of < +/- 2.5 degrees in the 9-11 microm (CO(2) laser) IR spectral range. This device functions as a linear-to-circular polarization transformer and can be tuned to exact QWR at any desired wavelength (within a given range) by tilting the prism by a small angle around phi =45 degrees. A PbTe right-angle prism introduces near-half-wave retardation (near-HWR) with a < or =2% error over a broad (4< or =lambda< or =12.5 microm) IR spectral range. This device also has a wide field of view and its interesting polarization properties are discussed. A compact (aspect ratio of 2), in-line, HWR is described that uses a chevron dual Fresnel rhomb with four TIRs at the same angle phi =45 degrees. Finally, a useful algorithm is presented that transforms a three-term Sellmeier dispersion relation of a transparent optical material to an equivalent cubic equation that can be solved for the wavelengths at which the refractive index assumes any desired value.

The lifetime of the first electronically excited state of sodium-ammonia (Na(NH3)n) clusters is investigated with femtosecond laser pulses in the visible and near IR spectral range. The decay time of the pump-probe ion signal decreases drastically with increasing cluster size from 1000 ps (n=l) to 0.1 ps for n = 15. Different decay mechanism are discussed. A purely statistical process can be excluded to be responsible for the observed decay times.KeywordsExcited StateFemtosecond Laser PulseProbe PulseSolvation ShellSodium AtomThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The lifetime of the first electronically excited state of sodium-ammonia (Na(NH3)n) clusters is investigated with femtosecond laser pulses in the visible and near IR spectral range. The decay time of the pump-probe ion signal decreases drastically with increasing cluster size from 1000 ps (n=l) to 0.1 ps for n = 15. Different decay mechanism are discussed. A purely statistical process can be excluded to be responsible for the observed decay times.

The reflectance and temperature of the boundary surface layer of marine surface are determined under natural conditions in the presence of the wind wave using the remote sensing of the radiation of marine surface and atmosphere in the IR spectral range. The permittivity of water is determined in the layer where the radiation is generated (1.5–2.0 thicknesses of skin layer). It is demonstrated that the permittivity of the film layer under natural conditions is a variable quantity that is less than the permittivity of sea water in the laboratory measurements, which is employed in the conventional procedures for the determination of the ocean temperature fields. The data of the measurements under natural conditions are interpreted using the model of a single layer with the skin-layer thickness of at least 10 μm that contains a static mixture of water and air microbubbles formed under the surface-tension film.

The aim of the given paper is to study experimentally the process of the particle trapping and transportation by means of the singular beams in the IR spectral range. As a rule, the micro particles trapping and transportation are usually accomplished by low-intensity laser beams. The fact is that the main instrument of this process is an axial optical vortex. But at present such a singular beams are created at the expense of computer-generated holograms. It is revealed that this technique enables us to generate singular beams in the IR spectral range at least 30 W in light power with the energetic efficiency near 100%

The reflectivity spectra and the magnetorefractive effect (MRE) of (Co50Fe50)x(Al2O3)1−x metal-dielectric granular films (0.07<x<0.52) are analyzed in the IR spectral range λ=2.5–25 µm. It is revealed that the specific features observed in the spectra at λ≈8.5 and 20 µm are associated with the excitation of phonon modes in the dielectric matrix. The magnetorefractive effect in the films is observed below the percolation thresh-old only in p-polarized light and above the percolation threshold for both the p and s polarizations. It is demonstrated that the optical properties of (Co50Fe50)x(Al2O3)1−x films in the IR spectral range, to a first approximation, can be interpreted in the framework of the effective-medium theory and the magnetorefractive effect can be explained in terms of the modified Hagen-Rubens relation.

Carbon-rich amorphous silicon carbide and silicon carbonitride films for silicon-based photoelectric devices and optical elements: Application from UV to mid-IR spectral range

The Planetary Spectroscopy Laboratory (PSL) of DLR in Berlin provides spectral measurements of primarily planetary analogues from the visible to the far-infrared range. PSL has supported the data analysis as well as the development and calibration of instruments for planetary missions from ESA, NASA and JAXA. For this purposes PSL provides reflection, transmission and emission spectroscopy of target materials. Currently PSL operates three identical Bruker Vertex 80V vacuum FTIR spectrometer (the third one just installed in June 2019), two spectrometers are equipped with aluminum mirrors optimized for the UV, visible and near-IR, the third features gold-coated mirrors for the near to far IR spectral range. External simulation chambers are attached to two of the instruments for emissivity measurements. The chamber at the near to far IR instrument allows emissivity measurements from 0.7-200 μm under vacuum for sample temperatures from 320K to above 900K, using an innovative induction system. The second chamber (purged with dry air and water cooled to ≤270K) allows emissivity measurements of samples with surface temperature from 290K to 420K. We measure bi-directional reflectance of samples; with variable incidence and emission angles between 0° and 85° (minimum phase angle is 26° to prevent damages to the mirrors). Samples are measured currently at room temperature and 170K, with a planned extension for temperatures below 100K, by means of a new external chamber, whose funding is accepted and will be available in 2020. Bi-directional and hemispherical reflectance is measured under purging/vacuum conditions, covering the 0.2 to above 200 μm spectral range. An FT-IR microscope installed at the end of 2018, allows microscopic analysis in transmission and reflectance in the VIS+VNIR+MIR spectral range. Transmission of thin slabs, optical filters, optical windows, pellets, and others is measured in the complete spectral range from UV to FIR using a parallel beam configuration to avoid refraction

It is well known that the optical materials are unique and perspective. Optical materials and the devices based on them are operated in the broad spectral range: In the UV spectral range (where the wavelength l is approximately placed in the range of ~ 0.1 - 0.4 microns), in the VIS spectral range (l ~ 0.5 - 0.75 microns), and in the IR spectral range (l is larger than the 0.75-1 microns). These materials can be considered to resolve the different complicated tasks. To study optical materials different techniques and methods should be scrupulously used. Among different applied methods namely the laser oriented technique and nanostructuration approach have some unique features. It can be considered as the effective dominant approach in order to reveal the change of all basic physical-chemical characteristics of the materials. Our own steps in this direction have partially been recently shown too. In the current paper, advantages of the modification of optical material surfaces via a nanotechnology approach will be shown. The surface relief change provokes the spectral, mechanical and wetting phenomena changes. A CO2-laser is applied to modify the optical materials surfaces under the condition when the carbon nanotubes are deposited in vertical position at the materials surfaces. This process permits to organize covalent bonding between the carbon atoms and the model matrix ones. An emphasis will be given on the surface modifications of the materials, such as: LiF, CaF2, KBr, BaF2, Sc, some polymer surface, etc. Mechanisms responsible for the spectral characteristics change, mechanical hardness as well as the increase of the wetting angle will be discussed. The area of the application of the materials studied can be increased.

Spectroscopy is still the most accurate methodology to remotely study the surface composition of celestial bodies (and its evolution). For more than ten years the Planetary Emissivity Laboratory (PEL) of DLR in Berlin has provided spectral measurements of planetary analogues from the visible to the far-infrared range for comparison with remote sensing spacecraft/telescopic measurements of extra-terrestrial surfaces [1-5]. Reflection, transmission and emission spectroscopy are the techniques we used to acquire spectral data of target materials.&#13;\nA recent major upgrade to our laboratory set-up added a new spectrometer, three external sources, optical units, new detectors and beamsplitters to further extend the spectral range of measurements that can be performed in the laboratory, as well as the temperature range that we can cover for the measurements. The purpose of this paper is to illustrate the very wide range of capabilities that the Planetary Spectroscopy Laboratory (PSL) can offer to the planetary and to the spectroscopic community.

The Special Ordered Structures of Specialty Fiber included into Multifunctional and Multi Channel Fiber Optic Bundles (MFOB) and Sensors are proposed. Optimal construction of fiber optic channels in the MFOB exhibit reduced speckle noise and high intensity transmission resulting from spatial homogeneity and symmetry of radiation. Improved new type of the Fibers: Metal Coated Multimode, Special Plastic Coated, Fibers for UV-VIS, Fibers for VIS-NIR spectral Range, Fibers for NIR and IR spectral range. Hexagonal package of sensitive end of the MFOB structures designed with different type and fiber core diameters fibers are transferred into the different configured input/output optical channels. For fluorescence spectroscopy and FDT Diagnostic described optimal arrangement with 7-256 Fibers included into MFOB structure. Remote spectroscopic Probes are used for "in Vivo" or "in Vitro" experimental devices. Sensors with MFOB probes bifurcated from two up to seven channels are used for process photometry and for mini-fiber spectrometric devices. Customized Software and flexible numerical simulations for data analysis are based into two levels of programming: -micro program part for ATMEL microprocessor, Visual C++ version 6.0 for PC computers with Windows -98-2000Me Programs. Advanced Applications of MFOB type of probes show some features for Biomedical Remote Sensing Systems: High Optical Throughput for Special Fluorescence Probes; High Stability for fool spectral range; Minimal cross link between fibers into MFOB-M structures; High stability for Endoscopes and sterilization proof tested solutions; Quality Controlled Scattered Reflection MFOB. MFOB structures designed with Mini Fiber Spectrometers show high spectral resolution (7 - 12 nm) and possibility to combine in one set different function: Normalization function for different light sources, Multi scan measurements with adjusted time duration, Spectral band analysis (including integrated characters for selected wavebands), Fast time resolution for selected types of scanning characters.

We successfully obtained transfer ribonucleic acid (tRNA) thin solid films (TSFs) using an aqueous solution precursor in an optimized deposition process. By varying the concentration of RNA and deposition process parameters, uniform solid layers of solid RNA with a thickness of 30 to 46 nm were fabricated consistently. Linear absorptions of RNA TSFs on quartz substrates were experimentally investigated in a wide spectral range covering UV–VIS–NIR to find high transparency for λ > 350 nm. We analyzed the linear refractive indices, n(λ) of tRNA TSFs on silicon substrates by using an ellipsometer in the 400 to 900 nm spectral range to find a linear correlation with the tRNA concentration in the aqueous solution. The thermo-optic coefficient (dn/dT) of the films was also measured to be in a range −4.21 × 10−4 to −5.81 × 10−4 °C−1 at 40 to 90 °C. We furthermore characterized nonlinear refractive index and nonlinear absorption of tRNA TSFs on quartz using a Z-scan method with a femtosecond laser at λ = 795 nm, which showed high potential as an efficient nonlinear optical material in the IR spectral range.