<title>Multichannel fiber optic bundles and sensors for biomedical application</title>

Combining near and mid infrared spectroscopy for heavy oil characterisation

In this paper, we present a manual for the preparation of fully functional woodpile structures with partial photonic band gap (PBG) for applications in the visible (VIS) spectral range using an attractive polymer IP-Dip that is novel in photonic applications. In an experimental preparation of polymer-based woodpile structures using the IP-Dip polymer with partial PBG in VIS spectral range, a single-step laser lithography technique based on direct laser writing (DLW) was used. The woodpile structure preparation is based on a complex theoretical analysis of dispersion diagrams for the woodpile structure with fcc symmetry and IP-Dip polymer. We found partial PBGs in the Γ - X direction and dependence of PBG on the filling factor. Using a conventional DLW lithography system, we prepared a series of low-periodic woodpile structures with PBG in NIR and VIS spectral range attacking the yellow-green spectral range, which can be easily applied on different photonic components.

We compared the heating and cooling theoretical and experimental transient times of DyPO4 nanoparticles as a result of their heating by themultiphonon relaxation after femtosecond laser excitation in the near IR spectral range into different absorption spectral lines of the Dy3+ ion. We have shown that the relaxation of the heat flux to a stationary value occurs according to an exponential law. Depending on the value of the Biot number, two different relaxation mechanisms can be realized, in one of which the relaxation time depends on the thermal conductance of the interface, and in the other on the thermal diffusivity. It is shown that, after averaging over the ensemble of nanoparticles, the kinetics of the relaxation of the heat flux in these limiting cases has a substantially different character. The results might be helpful for assessing the prospects of the dielectric crystalline nanoparticles doped with rare-earth ions in the local hyperthermia treatment of cancer cells.

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.

Spectral inter-conversion analysis of thermally induced structural changes in polyethylene crystals

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

The Optical Head design of the Moons And Jupiter Imaging Spectrometer (MAJIS), is presented. MAJIS is a compact visible and near-infrared imaging spectrometer covering the spectral range from 0.5 to 5.54 μm split into two channels, designed for the JUpiter ICy moons Explorer (JUICE) mission [1], that will conduct an in-depth study of the Jupiter system, with particular emphasis on Jupiter, Ganymede, Callisto and Europa. The MAJIS optical layout is constituted by a fore optics, slit and collimator shared between the two channels (VIS-NIR from 0.5 to 2.35 μm and IR from 2.25 to 5.54 μm), followed by a dichroic filter that splits the light between the channels, each one endowed with its own grating, objective and detector. The two focal plane arrays have a matrix of 400×508 (pixel×spectel), 36 μm pitch. A flat mirror mounted in a SU (Scan Unit) before the telescope allows scanning the line of sight in a direction perpendicular to the slit, so to achieve either imaging of a fixed target or motion compensation to increase the dwell time when in close approach periods (e.g. during flybys). In addition, a calibration unit is realized to allow both radiometric and spectral calibration of the two channels, using two different light sources (an incandescent lamp and a black body) that illuminate a common diffuser. Mechanical design is based on a single optical bench which is populated on both sides for volume optimization. The bench implements a network of internal ribs plus a continuous peripheral rib to maximize the stiffness/mass ratio. Three bipods in composite material constitutes the interface with the S/C bench. Bipods design is the result of an accurate trade between thermal insulation from the spacecraft and structural stiffness, still minimizing stresses induced on the bench due to the temperature gradient between the Optical Head and the S/C bench. Low Optical Head operative temperature (<140 K) and cryogenic IR detector temperature (<90 K), required for proper operations in the IR spectral range, are achieved through passive cooling. Two large radiators are implemented on top of the Optical Head, which are in view of the cold space. Double layer of SLI and MLI provides the necessary radiative insulation from the surrounding environment.

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 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 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

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.

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.

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.

Optical polarizability tensor and absorption tensor in (fluoranthen) 2PF 6

The reconnaissance capability of a military observation and targeting platform is mainly driven by the performance of the used sensors. In general, the MWIR thermal imager is the primary sensor and the use of a visible camera increases the identification capability of the platform during day for very long observation ranges. In addition to the imaging sensors a laser pointer, a laser rangefinder (LRF), and a combined laser rangefinder/ designator (LRF/D) completes the sensor suite. As LRF a single pulse eye safe rangefinder based on an OPO shifted Nd:YAG transmitter can be used. The alternative LRF/D uses an diode laser pumped dual wavelength OPO/Nd:YAG transmitter and can be operated either at 1570 nm or at 1064 nm with a pulse rate of maximum 25 pps [1]. A MWIR thermal imager [2] with a 1280x1024 MWIR detector and an optical zoom range between 1.2° and 20° horizontal fields of view provides a HD-SDI video stream in the 720p or 1080p standard. A camera build in software image stabilizer and a smart tone mapping algorithm improves the reconnaissance results for the observer. A combined camera covers the visible, NIR and SWIR spectral range [3] using a common entrance optics. The resolution of the color camera Si-CMOS chip is 1920x1080 and of the InGaAs focal plane array it is 640x512 detector pixel. The combined VIS/NIR/SWIR camera provides improved ranging under hazy and misty atmospheric conditions and also improved detection of laser spots e.g. of the integrated laser designator with high sensitivity in the spectral range between 450 nm up to 1700 nm, most of the military lasers are operating in the NIR and SWIR spectral band [3]. The combination of the sensors in the platform improves significantly the operational use. The application of the described platform is not limited to military scout vehicles, the available sensors are also integrated in a targeting platform with similar performances but other environmental demands. The possibilities, improvements in comparison of existing platforms and potential upgrades are discussed.