In this study, we used dual-side nanoimprint lithography to prepare sub-wavelength periodical grating (SPG)-based wave plates on flexible substrates. Without employing any etching, we directly imprinted SPGs on both sides of a polycarbonate (PC) substrate through a one-step imprinting process. This dual-side nanoimprint lithography process dramatically decreases the typical imprinting pressure required in conventional resist-based nanoimprint lithography. With this low-cost formation of PC-based wave plates, any degree of phase retardation could be obtained merely by stacking a set of wave plates with designed depths and working wavelengths. Our SPG-based wave plates exhibited the excellent broadband antireflection properties of sub-wavelength structures possessing refractive index gradients on both sides of the PC substrates. The high flexibility, low cost, and low surface reflection of these dual-side SPG-based wave plates make them attractive alternatives to commonly used birefringent crystal-based wave plates, suggesting that this phase retardation technique has promising potential for use in the development of next-generation flexible optoelectronic devices and systems.Wave plates are key components in various optoelectronic systems because they can modulate the polarization state of light through phase retardation effects along their fast and slow axes. 1 In an optics system, a 0.5p phase retardation is usually obtained using a quarter-wave plate. When light passes through a quarterwave plate, a 0.5p phase retardation is applied to the electric field passing through the slow axis; therefore, a 0.5p phase difference exists between the electric fields emitted from the fast and slow axes of the wave plate. Meanwhile, a 0.5p phase retardation would be achieved when stacking two 1/8-wave plates together. The eventual polarization state of the light would be identical to that of light that had passed directly through a quarter-wave plate. Thus, arbitrary phase retardation could be achieved if we precisely stacked numbers of wave plates with designed phase retardation. Under this consideration, low-cost wave plates were in demand.Commercial wave plates are typically made of highly crystalline birefringent crystals, such as quartz, calcite, and MgF 2 , which exhibit different refractive indices along their different crystalline orientations. 2-4 Difficulties encountered during the cutting, grinding, and polishing of these crystal-based wave plates mean that they are generally expensive. Moreover, because birefringent crystals exhibit intrinsically high reflection at their surfaces, additional antireflection coatings on both surfaces of a plate are necessary to ensure high transmittance of incident light and to eliminate stray light.Recently, phase retarders made of liquid crystal cells have been developed as alternatives to inorganic crystals. The large birefringence of these liquid crystals makes them promising phase modulators. A liquid crystal cell has the potential to behave both as a phase rotation and retarda...
A: Beam commissioning of the SuperKEKB collider began in 2016. The Beam Exorcism for A STable experiment II (BEAST II) project is particularly designed to measure the beam backgrounds around the interaction point of the SuperKEKB collider for the Belle II experiment. We develop a system using bismuth germanium oxide (BGO) crystals with optical fibers connecting to a multianode photomultiplier tube (MAPMT) and a field-programmable gate array (FPGA) embedded readout board for monitoring the real-time beam backgrounds in BEAST II. The overall radiation sensitivity of this system is estimated to be (2.20 ± 0.26) × 10 −12 Gy/ADU (analog-todigital unit) with the standard 10 m fibers for transmission and the MAPMT operating at 700 V. Our γ-ray irradiation study of the BGO system shows that the exposure of BGO crystals to 60 Co γ-ray doses of 1 krad has led to immediate light output reductions of 25-40%, and the light outputs further drop by 30-45% after the crystals receive doses of 2-4 krad. Our findings agree with those of the previous studies on the radiation hard (RH) BGO crystals grown by the low thermal gradient Czochralski (LTG Cz) technology. The absolute dose from the BGO system is also consistent with the simulation, and is estimated to be about 1.18 times the equivalent dose. These results prove that the BGO system is able to monitor the background dose rate in real time under extreme high radiation conditions. This study concludes that the BGO system is reliable for the beam background study in BEAST II. K: Front-end electronics for detector readout; Radiation-hard detectors; Radiation damage to detector materials (solid state); Radiation monitoring A X P : 1705.00312
The hole mobility of relaxed Ge channel, and strained Ge channel on relaxed Si0.6Ge0.4 substrate were simulated and compared to our experimental work (Al2O3/GeO2 gate stack) and previous data. The rougher interface at GeO2/Ge than SiO2/Si makes a faster roll-off of Ge hole mobility at high field. For SiO2/Ge interface, the Ge hole mobility has a similar roll-off as Si universal mobility. Ge has higher mobility enhancement than Si under uniaxial compressive stress along [110] direction. For composite uniaxial compressive stress (-3GPa) and biaxial compressive strain (2.4%) on Ge p-MOSFETs, Ge mobility enhancement can reach as high as 23 times of Si mobility. The mass reduction of Ge is mainly responsible for the mobility enhancement.
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