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250-page monograph on diffraction gratings: design, manufacture & use
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... Because the blackbody has continuous emission spectra, the whole image should be bright. If the gas is present in the tube, and it absorbs infrared radiation at certain wavelengths, one will see it as dark absorption vertical lines (or bands) [2]. ...
... where: Iintensity of radiation after passing the tube I0initial intensity of radiation before entering the tube aabsorption coefficient of the gas inside tube, which is linearly dependent on its concentration Llength of the tube boffset value required for curve fitting with measured differential data During the curve fitting process, the best matching values of I0 = 190.14, L=0.055 and b=196.32 were found, enabling us to plot the calibration curve in fig. 6 using equation (2). As it may be observed, this calibration curve is very close to real measurement. ...
... What is important, it is possible to calculate calibration curves for different lengths of the tube, using equation (2). Let us check this dependence for tube lengths equal to 25 cm, 50 cm (original size), 100 cm and 200 cmthe results are shown in fig. 7. 10.21611/qirt.2016.095 ...
The aim of this paper is to demonstrate the application of reflective diffraction grating and MWIR thermal camera for identification of gas and estimation of its concentration. For this purpose a special rig was created with airtight tube that was filled with different mixtures of carbon monoxide, carbon dioxide and nitrogen. Thanks to infrared windows at both sides of this tube, the radiation from blackbody could pass through it and diffract at the reflective diffraction grating to finally reach the camera. After spectral calibration this rig may be used to identify gas in a tube, because different gases have different absorption bands. Measuring signal in the absorption band one can estimate the concentration of gas in a tube.
... Since the color effects reported in the present work not only rely on zero order transmittance (T0) but also ±1st orders transmittances (T1/T−1), I would like to revisit equation [2−1]. As asymmetric gratings are considered, the sign of the incident angle is important and must be chosen as shown in Figure 38 (b), following grating standards, as defined for example in [216]. Throughout the rest of this section, the color code shown on this image will be kept for T0, but not for the ±1st order. ...
... In order to excite plasmonic resonances in 1D gratings, the polarization of the incident electric field has to be perpendicular to the grating lines (TM or p−polarized light in classical mount and TE or s−polarized light in conical mount [216]). This configuration provides confinement for the charges, which is necessary for LSPRs to occur, as well as a suitable orientation of the electric field vector for launching SPPs (compare to Section 2.2.2). ...
... In the present case, the grating equation needs to be adapted for conical incidence and the diffraction angle can be calculated with [216]: [5−5] where n1 is the refractive index of the cover material, Λ the period of the grating, m the diffraction order, the angle of incidence with respect to the surface normal along the wires and λ the wavelength of the impinging radiation. For = 1.41, = 350 nm, = 6° and = 1 a diffraction angle of ( ) = 90° is achieved at ≈ 490 nm. ...
Since most of the academic photonic and plasmonic nanostructures are based on slow and expensive electron beam lithography processes, there is a need for innovative alternatives suitable for industrial manufacturing. Large areas need to be patterned with a high throughput, which is for example achieved with roll-to-roll machines. Up-scalable designs of photonic and plasmonic nanostructures are therefore studied in this thesis. Typical industrial processes include embossing and evaporation, which are consequently used throughout the thesis. I propose oblique evaporation of high refractive index materials to render binary gratings highly efficient for first order transmission. Zinc sulfide coatings are employed to diffract close to 70% of unpolarized green light. Simulations further show that they can be encapsulated to protect them from environmental influences like humidity, wear or dust, while retaining their exceptional diffractive properties, which is very appealing for outdoor applications. I also show that thin metallic coatings can attain similar efficiencies for TE polarized light. The effect is asymmetric and shows a maximum at the Wood-Rayleigh anomaly, which results in orientation dependent coloration of the zero order as well as first order transmittances. A large part of the standard RGB gamut can be covered through proper adjustment of the grating parameters. Combination of zero order and first order effects allows creation of color appearances that switch when rotating or flipping the device. I finally present how floating images become apparent when a patterned light source like e.g. a mobile phone is used in conjunction with the metallized grating. Direct transfer of plasmonic technology from universities to industry is often not possible: in academia, metallic nanostructures often require a lateral resolution of a few nanometers, which is challenging to achieve in up-scalable processes. Thicknesses on the other hand can be controlled in this regime using evaporation techniques, which are hence powerful methods for high-throughput production. In this thesis, Fano-resonant, U-shaped nanowires are created with oblique metal deposition. In order to make them available for mass-production, aluminum is chosen as the plasmonic material. The surface integral equation method is used to investigate near-fields and charge distributions, which shed light onto the physics behind the present resonances. A surface plasmon polariton is found to couple to a localized plasmonic mode with a hexapolar charge distribution. It is finally shown that the Fano-resonance can be accurately tuned by adapting evaporation angle and metal thickness. These two parameters can easily be accessed and would allow for good control over the optical response even in an industrial environment. The applicability of the above insights is then demonstrated by creating a strain sensor. To that end, the process is transferred to a stretchable polymer and when elongating the structure perpendicular to the wires, the polymeric spacing between them is expanded. The sensitivity of the Fano-resonance to this change in inter-wire distance is investigated and a strong damping is observed. Through careful design, a clearly visible color switch from purple to green is achieved for elongations less than 20%. The sensor was deemed to be very durable, as no deterioration in the color or the spectral response was observed even after several strain cycles.
Традиційна фокусуюча лінза Френеля концентрує інтенсивність світла в центр сформованого зображення. Однак іноді необхідно перетворювати паралельний потік променів у світлове коло. Такі трансформуючі плоскі лінзи Френеля часто використовуються в системах обробки сигналів. Наведено алгоритм моделювання мікропризматичних структур Френеля, які формують у фокальній площині рівномірно освітлене коло. Цей алгоритм подібний до алгоритму моделювання, розробленого для створення фокусуючих мікропризматичних елементів з плоскими кільцевими фокусуючими гранями. Запропоновані структури з дискретною зміною кутів заломлення для трансформації світлових потоків можна легко виготовити методом алмазного різання, який дозволяє отримувати плоскі конусні робочі поверхні високої оптичної якості. Розмір призматичних заломлюючих зон не повинен бути занадто великим для зменшення дискретності сформованих зображень. Тому передбачається створення зон заломлення з декількох однакових малих мікропризм. Запропоновано модифікований алгоритм моделювання параметрів трансформуючої лінзи, який враховує процеси концентрації світла лінзою та звуження світлових потоків мікропризмами.
Dichromated gelatins are commonly fabricated with ammonium dichromate as a sensitizer. A less common alternative is to employ potassium dichromate, due to the unable characterization information of such process. This article aims to prove the efficiency of potassium dichromate as a sensitizer in dichromated gelatins without a development process. The study was performed measuring in real-time the diffraction efficiency of holographic gratings recorded in gelatin sensitized with potassium dichromate as a photosensitive material. The holographic gratings were recorded with an Ar laser with a 532 nm wavelength varying parameters in the photosensitive material such as cell thickness, concentration between gelatin and potassium dichromate as well as the angle of interference between the two light beams and the laser power. The optimum parameters combination yielded a 19% of diffraction efficiency at the first diffraction order and allowed to record Fourier holograms. The results obtained prove the good performance of potassium dichromate as a sensitizer. Furthermore, the recording of holograms in the dichromated gelatin proposed here could be a very efficient way to make diffractive elements for uncomplicated practices in university laboratories due to it can be massively produced in any laboratory with minimum requirements at low cost.
State-of-the art computers need high performance transistors, which consume ultra-low power resulting in longer battery lifetime. Billions of transistors are integrated neatly using matured silicon fabrication process to maintain the performance per cost advantage. In that context, low-cost mono-crystalline bulk silicon (100) based high performance transistors are considered as the heart of today's computers. One limitation is silicon's rigidity and brittleness. Here we show a generic batch process to convert high performance silicon electronics into flexible and semi-transparent one while retaining its performance, process compatibility, integration density and cost. We demonstrate high-k/metal gate stack based p-type metal oxide semiconductor field effect transistors on 4 inch silicon fabric released from bulk silicon (100) wafers with sub-threshold swing of 80 mV dec(-1) and on/off ratio of near 10(4) within 10% device uniformity with a minimum bending radius of 5 mm and an average transmittance of ~7% in the visible spectrum.
