Surface plasmon enhanced light-emitting diode

A method for enhancing the emission properties of light-emitting diodes, by coupling to surface plasmons, is analyzed both theoretically and experimentally. The analyzed structure consists of a semiconductor emitter layer thinner than λ/2 sandwiched between two metal films. If a periodic pattern is defined in the top semitransparent metal layer by lithography, it is possible to efficiently couple out the light emitted from the semiconductor and to simultaneously enhance the spontaneous emission rate. For the analyzed designs, we theoretically estimate extraction efficiencies as high as 37% and Purcell factors of up to 4.5. We have experimentally measured photoluminescence intensities of up to 46 times higher in fabricated structures compared to unprocessed wafers. The increased light emission is due to an increase in the efficiency and an increase in the pumping intensity resulting from trapping of pump photons within the microcavity

Methods for controlling positions of guided modes of photonic-crystal waveguides

We analyze different methods for controlling positions of guided modes of planar photonic-crystal waveguides. Methods based both on rearrangements of holes in the photonic-crystal lattice and on changes of hole sizes are presented. The ability to tune frequencies of guided modes within a frequency bandgap is necessary to achieve efficient guiding of light within a waveguide, as well as to match frequencies of eigenmodes of different photonic-crystal-based devices for the purpose of good coupling between them. We observe and explain the appearance of acceptor-type modes in donor-type waveguides

Design and Fabrication of Silicon Photonic Crystal Optical Waveguides

We have designed and fabricated waveguides that incorporate two-dimensional (2-D) photonic crystal geometry for lateral confinement of light, and total internal reflection for vertical confinement. Both square and triangular photonic crystal lattices were analyzed. A three-dimensional (3-D) finite-difference time-domain (FDTD) analysis was used to find design parameters of the photonic crystal and to calculate dispersion relations for the guided modes in the waveguide structure. We have developed a new fabrication technique to define these waveguides into silicon-on-insulator material. The waveguides are suspended in air in order to improve confinement in the vertical direction and symmetry properties of the structure. High-resolution fabrication allowed us to include different types of bends and optical cavities within the waveguides

Changes in Levels of Economic Development among the States Formed in the Area of Former Yugoslavia

After a long period, during the Yugoslav epoch, in which there were o changes in the levels of economic development of the constitutive republics, major changes occurred following the break-up of Yugoslavia. The western republics – today independent Slovenia and Croatia – rapidly advanced and notably diverged from the former eastern republics. The range of differences in development levels became surprisingly large in the area of the former shared state. At the same time, economic cooperation between countries in the ex-Yugoslav area decreased. Most recently there has been an increase in such cooperation, yet its extent is still much lower than before the break-up of Yugoslavia. The present differences in the levels of development between the western and the eastern states (independent countries) will presumably decrease in the future – however, for some time to come, for at least one or two decades, these differences will remain greater than they were during the period before 1990, i.e. when the Federal Socialist Republic of Yugoslavia still existed

Industrial restructuring and downsizing: Case study of Central Croatia

The collapse of socialist economic system in Croatia was followed by a period of economic transition during which the industry sector was affected by major changes. This study, on an example of Central Croatia, analyzes the spatial aspect of these changes between 1990 and 2011. The used data were taken from the National Bureau of Statistics and studies in which the transition period industry is researched from economic and geographical point of view. Calculations of most indicators referred to a county level while some indicators were calculated at the level of administrative cities and municipalities. It was found that, in Central Croatia, there had come to a process of deindustrialization, and in some rare cases a process of reindustrialization, an increase in importance of tertiary and quaternary activities, and calculation of some indicators such as degree of industrialization, location quotient, regional factor and index of specialization indicated on the existence of significant differences between individual parts of Central Croatia

Photonic crystals for confining, guiding, and emitting light

We show that by using the photonic crystals, we can confine, guide, and emit light efficiently. By precise control over the geometry and three-dimensional design, it is possible to obtain high quality optical devices with extremely small dimensions. Here we describe examples of high-Q optical nanocavities, photonic crystal waveguides, and surface plasmon enhanced light-emitting diode (LEDs)

Participation of non-party organizations and groups in the elections in Serbia

Uverenje da su političke partije ključni akteri političkog predstavljanja podložno je sve većim kritikama kako opada identifikacija birača sa partijama i raste antipartizam. Paralelno sa tim u literaturi raste interesovanje za nepartijske organizacije i kandidate na izborima i mogućnosti da ovi akteri doprinesu novim modelima demokratije i demokratičnijem predstavljanju. S druge strane, u Srbiji je učešće nepartijskih organizacija na izborima gotovo u potpunosti neistraženo uprkos tome što se poslednjih godina na izborima pojavljuje sve više nepartijskih lista, odnosno grupa građana. Ovaj rad stoga analizira učešće nepartijskih organizacija na izborima u Srbiji sa ciljem da istraži pravilnosti u njihovom izbornom učešću i rezultatima i vezu između sve veće pojave grupa građana na izborima i sve većeg nepoverenja birača u političke partije.The belief that political parties are key actors of political representation is increasingly criticized as voters’ identification with political parties declines and antipartisanship grows. At the same time, there is a growing academic interest in the electoral participation of non-party organizations and candidates and opportunities for these actors to contribute to new models of democracy and more democratic representation. On the other hand, in Serbia, the participation of non-party organizations in the elections is almost completely unexplored, despite the fact that in recent years non-party lists, i.e. groups of citizens, have increasingly been participating in the elections. This paper there- fore analyzes the participation of non-party organizations in the elections in Serbia in order to explore the patterns in their electoral appearance and results, and the connection between the growing electoral participation of groups of citizens and a growing distrust of voters in political parties

Belgrade city assembly elections 2022 – actors, results and consequences

Izbori za skupštinu glavnog grada 3. aprila 2022. godine su iz više razloga bili posebno zanimljivi i značajni. Prvo, to su jedini izbori na kojima je postojala bar delimična neizvesnost u pogledu izbornih rezultata. Dok se na predsedničkim i parlamentarnim izborima očekivala ubedljiva pobeda Srpske napredne stranke (SNS), beogradski izbori su jedini gde se u toku izborne kampanje verovalo da bi opozicija mogla da osvoji dovoljan procenat glasova da uzdrma stabilnu osmogodišnju vladavinu SNS. Drugo, bacili su svetlo na dinamiku i podele unutar SNS. Utapanje u SNS Srpskog patriotskog saveza (SPAS) Aleksandra Šapića koji je na prethodnim beogradskim izborima 2018. godine bio drugi po snazi, uticalo je na podele unutar vladajuće stranke, i još važnije,na promenu beogradske političke scene. Treće, predviđanja u toku izborne kampanje su potvrđena izbornim rezultatima. Za razliku od izbora 2014. i 2018. godine kada je SNS imao preko 50% mandata i mogao samostalno da formira vlast, nakon što su 2022. godine objavljeni rezultati izbora na trenutak je delovalo da SNS ni sa svojim dugogodišnjim koalicionim partnerima ovaj put neće imati većinu. Imajući u vidu značaj izbora i kontekst u kom se održavaju, u ovom radu se analiziraju faktori koji utiču na proces održavanja beogradskih izbora, rezultati, proces formiranja vlasti i posledice izbora

Globalizacija i/ili održivi razvoj?

Danas je, više nego ikada, očito kako je daljnji ekonomski pa i cjelokupni društveni razvoj, na nacionalnoj, ali i na globalnoj razini postao ovisan o održivom razvoju. Također, globalizacija ukazuje da gospodarski razvoj i sve promjene koje se odnose na njegove postojeće strukture, mora održivi razvoj uzeti kao mjerilo stvaranja novih globalnih veza koje će se temeljiti na pravednosti, podjednakoj raspodjeli bogatstva i novom konceptu globalnog razvoja uopće