14 research outputs found
Phase distortion corrections of phase-only LCOS devices for digital holographic applications
No full text© OSA 2019 © 2019 The Author(s) Significant phase distortion corrections of nearly perfect phase linearity and minimum phase flicker with doubled meaningful phase levels was achieved by optimising the digital driving patterns of phase-only LCoS devices for digital holographic applications
Phase distortion corrections of phase-only LCOS devices for digital holographic applications
No full text© OSA 2019 © 2019 The Author(s) Significant phase distortion corrections of nearly perfect phase linearity and minimum phase flicker with doubled meaningful phase levels was achieved by optimising the digital driving patterns of phase-only LCoS devices for digital holographic applications
Citizenship, Co-ethnic Populations and Employment Probabilities of Immigrants in Sweden
No full textOver the last decades, Sweden has liberalized its citizenship policy by reducing the required number of years of residency to five for foreign citizens and only two for Nordic citizens. Dual citizenship has been allowed since 2001. During the same period, immigration patterns by country of birth changed substantially, with an increasing number of immigrants arriving from non-western countries. Furthermore, immigrants were settling in larger cities as opposed to smaller towns as was the case before. Interestingly, the employment integration of immigrants has declined gradually, and in 2006 the employment rate for foreign-born individuals is substantially lower compared to the native-born. The aim of this paper is to explore the link between citizenship and employment probabilities for immigrants in Sweden, controlling for a range of demographic, human capital, and municipal characteristics such as city and co-ethnic population size. The information we employ for this analysis consists of register data on the whole population of Sweden held by Statistics Sweden for the year 2006. The basic register, STATIV, includes demographic, socio-economic and immigrant specific information. In this paper we used instrumental variable regression to examine the "clean" impact of citizenship acquisition and the size of the co-immigrant population on the probability of being employed. In contrast to Scott (2008), we find that citizenship acquisition has a positive impact for a number of immigrant groups. This is particularly the case for non- EU/non-North American immigrants. In terms of intake class, refugees appear to experience substantial gains from citizenship acquisition (this is not, however, the case for immigrants entering as family class). We find that the impact of the co-immigrant population is particularly important for immigrants from Asia and Africa. These are also the countries that have the lowest employment rate.citizenship, naturalization, immigration, ethnicity
Harnessing high-aspect-ratio dimer metasurface for efficient liquid crystal alignment and tunable optical elements
No full textIn this study, we systematically investigate the effect of the aspect ratio (AR) of metasurface features on liquid crystal (LC) alignment. Experimental results reveal that an AR of at least 5 is necessary for effective alignment. Based on this, we design and fabricate an electrically tunable geometric-phase (GP) grating using a dimer metasurface with a maximum AR of 6.5. This configuration offers three key advantages: (1) the slot between dimers forms a high-AR region that facilitates LC alignment and shields it from external disturbances, (2) the enhanced electric field, concentrated near the slot, is parallel to the LC molecular direction, enabling effective resonance modulation, and (3) the halfwave condition is simultaneously provided by both the LC and metasurface through light propagation and electromagnetic resonance, enabling devices with a thin LC layer and hence fast switching speed. These features enable the realization of geometric-phase optical elements (GPOEs) with subwavelength pixel sizes using metasurfaces fabricated by mature and scalable lithographic techniques. The resulting device achieves a first-order diffraction efficiency of 83% at 1550 nm, with an amplitude modulation depth of ∼97% upon voltage application. Furthermore, a minimum switching frequency of 120 Hz is experimentally demonstrated. These findings present a promising strategy for creating high-efficiency and electrically tunable GPOEs with arbitrary spatial orientations—an essential requirement for applications such as holography—and advancing the development of next-generation optoelectronic and telecommunication devices
Multi-height metasurface for wavefront manipulation fabricated by direct laser writing lithography
No full textWe introduce two types of dielectric metasurfaces, consisting of 3 × 3 regions, which manipulate wavefront by different feature heights. Both polarization-dependent and polarization-independent metasurfaces are realized for phase depth of 0 ∼ 2π at 1550 nm, with considerable average transmittance of 80.1 and 85.1 %, respectively. The phase modulation capability can be extended over a broadband range of 1460.1–1618.0 nm for optical communications, by carefully designing nanofeature sizes. Moreover, the entire metasurfaces with nanofeatures of varying heights can be fabricated in a single process by using direct laser writing with high-precision, which is beneficial for mass production and promising in developing efficient and ultracompact devices
Pixel-level tunable liquid crystal lenses for auto-stereoscopic display
No full textMobile video and gaming are now widely used, and delivery of a glass-free 3D experience is of both research and development interest. The key drawbacks of a conventional 3D display based on a static lenticular lenslet array and parallax barriers are low resolution, limited viewing angle and reduced brightness, mainly because of the need of multiple-pixels for each object point.
This study describes the concept and performance of pixel-level cylindrical liquid crystal (LC) lenses, which are designed to steer light to the left and right eye sequentially to form stereo parallax. The width of the LC lenses can be as small as 20-30 μm, so that the associated auto-stereoscopic display will have the same resolution as the 2D display panel in use. Such a thin sheet of tunable LC lens array can be applied directly on existing mobile displays, and can deliver 3D viewing experience while maintaining 2D viewing capability.
Transparent electrodes were laser patterned to achieve the single pixel lens resolution, and a high birefringent LC material was used to realise a large diffraction angle for a wide field of view. Simulation was carried out to model the intensity profile at the viewing plane and optimise the lens array based on the measured LC phase profile. The measured viewing angle and intensity profile were compared with the simulation results
Colorimetric-based Detection of TNT Explosives Using Functionalized Silica Nanoparticles
No full textCitizenship and Employment - comparing two cool countries
No full textOver the last decades, both Canada and Sweden have liberalized citizenship regulations for permanent residents. During the same period, immigration patterns by country of birth have changed substantially, with an increasing number of immigrants arriving from non-western countries. The aim of this paper is to explore the link between citizenship and employment probabilities for immigrants in both countries, controlling for a range of demographic, human capital, and municipal characteristics such as city and co-ethnic population size. We use data from the 2006 Canadian census and Swedish register data (STATIV) for the year 2006. Both STATIV and the Census, include similar sets of demographic, socio-economic and immigrant specific. We use instrumental variable regression to examine the "clean" impact of citizenship acquisition and the size of the co-immigrant population on the probability of being employed in both countries. We find that citizenship acquisition has a positive influence on employment probabilities in both Canada and Sweden. The size of the co-ethnic population has a positive impact for many immigrant groups - as the co-ethnic population increases, the probability of being employed also increases.
