Focal plane arrays for submillimeter waves using two-dimensional electron gas elements: A grant under the Innovative Research Program

This final report describes a three-year research effort, aimed at developing new types of THz low noise receivers, based on bulk effect ('hot electron') nonlinearities in the Two-Dimensional Electron Gas (2DEG) Medium, and the inclusion of such receivers in focal plane arrays. 2DEG hot electron mixers have been demonstrated at 35 and 94 GHz with three orders of magnitude wider bandwidth than previous hot electron mixers, which use bulk InSb. The 2DEG mixers employ a new mode of operation, which was invented during this program. Only moderate cooling is required for this mode, to temperatures in the range 20-77 K. Based on the results of this research, it is now possible to design a hot electron mixer focal plane array for the THz range, which is anticipated to have a DSB receiver noise temperature of 500-1000K. In our work on this grant, we have found similar results the the Cronin group (resident at the University of Bath, UK). Neither group has so far demonstrated heterodyne detection in this mode, however. We discovered and explored some new effects in the magnetic field mode, and these are described in the report. In particular, detection of 94 GHz and 238 GHz, respectively, by a new effect, 'Shubnikov de Haas detection', was found to be considerably stronger in our materials than the cyclotron resonance detection. All experiments utilized devices with an active 2DEG region of size of the order of 10-40 micrometers long, and 20-200 micrometers wide, formed at the heterojunction between AlGaAs and GaAs. All device fabrication was performed in-house. The materials for the devices were also grown in-house, utilizing OMCVD (Organo Metallic Chemical Vapor Deposition). In the course of this grant, we developed new techniques for growing AlGaAs/GaAs with mobilities equalling the highest values published by any laboratory. We believe that the field of hot electron mixers and detectors will grow substantially in importance in the next few years, partly as a result of the opportunity given us through this grant, which represents the major effort in the US so far. We note, however, that parallel research on hot electron mixers in thin film superconductors in Russia, and recently in Sweden, have demonstrated mixing up to 1 THz, with the potential for low-noise receivers for frequencies up to many THz. The three groups recently assessed the relative adtantages of 2DEG and superconducting film mixers in a joint paper (Kollberg et al., 1992; see Appendix II)

Development of theoretical models of integrated millimeter wave antennas

Extensive radiation patterns for Linear Tapered Slot Antenna (LTSA) Single Elements are presented. The directivity of LTSA elements is predicted correctly by taking the cross polarized pattern into account. A moment method program predicts radiation patterns for air LTSAs with excellent agreement with experimental data. A moment method program was also developed for the task LTSA Array Modeling. Computations performed with this program are in excellent agreement with published results for dipole and monopole arrays, and with waveguide simulator experiments, for more complicated structures. Empirical modeling of LTSA arrays demonstrated that the maximum theoretical element gain can be obtained. Formulations were also developed for calculating the aperture efficiency of LTSA arrays used in reflector systems. It was shown that LTSA arrays used in multibeam systems have a considerable advantage in terms of higher packing density, compared with waveguide feeds. Conversion loss of 10 dB was demonstrated at 35 GHz

Near millimeter wave imaging/multi-beam integrated antennas

This report describes the most recent work on the theory of single element Linearly Tapered Slot Antennas (LTSAs) and Constant Width Slot Antennas (CWSAs). The radiation mechanism for these is presently well understood and allows quantitative calculation of beamwidths and sidelobe levels, provided that the antennas have a sufficiently wide conducting region on either side of the tapered slot. Appendices 4 to 7 represent earlier work on the grant. This work further elucidates the properties of arrays of CWSA elements, and the effects of coupling on the beam-shape. It should be noted that typical beam-efficiencies of 65% have been estimated, and that element spacings of about one Rayleigh unit are possible. Further, two-point resolution at the Rayleigh spacing has been demonstrated for a CWSA array in a 30.4 cm paraboloid at 31 GHz. These results underscore that interest in further studies of the radiation mechanism of tapered slot arrays. Appendix 7 constitutes a final, detailed report on the work leading to a 94 GHz seven element LTSA array imaging system, which has been reported previously in less detail. Experimental results are presented

The Social Impact of Remittances on Gender roles in Kosovo; a catalyst for Women Empowerment?

The aim of this thesis is to study how social remittance have impacted gender roles in household structures in Kosovo. By studying the ideas, norms, practices and social capitals sent from the migrant families to the residing families in the country of origin, I will examine if this has led to a change in Kosovar household structure. By conducting a field study, both surveys and interviews were carried out within the Kosovo Albanian households. The main focus of the analysis will be shed on the 33 interviews conducted that were carried out in seven different locations around Kosovo. This gives vital information regarding Kosovars perception of how the household structure has changed. The theoretical framework of the thesis consists of a nexus of theories with Peggy Levitt’s theory on Social remittance, Amartya Sen’s capabilities approach and New Economic of Labour migration theory. Together they create an understanding of the transmitting of ideas, how these ideas contribute to the capabilities of humans and shows how the migration pattern is connected to family based decisions. The thesis is concluded by pointing out the interviewees perception of an on-going change in gender roles in Kosovar household structures. The interviewees argue that the change is occurring due to three factors – a raising awareness among the population through globalisation, improved illiteracy and better access to education and finally, the impact of the ideas from the diaspora. In the final part of the analysis, we look at how social remittance can act as a catalyst for female empowerment in household structures

Transnational Adoption and European Immigration Politics: Producing the National Body in Sweden

This article explores the role of transnational adoption in the production of a multicultural but Swedish national body during the second half of the twentieth and the first decade of the twenty-first century, when Sweden became a multiethnic, multicultural, and racially divided country. I examine the development of international adoption policies in the 1970s, 1980s, and 1990s, emphasizing the erasure of the child\u27s connection to a preadoptive past, even as the child\u27s cultural difference was celebrated in adopting nations. In Sweden, which in the late 1970s and early 1980s had the world\u27s highest adoption ratio (number of transnational adoptions per 1000 live births), debates about the Swedishness of the adoptee and the difference of the immigrant child underscored the assumption that the former but not the latter could become completely Swedish, while hinting at the (in)significance of race in constituting Swedish identity. My research situates transnational adoption in the context of technologies of exclusion that regulate the national body and the complex position of the adoptee as an incorporated but excluded other in adopting nations. Globalization and Migration Symposium, Indiana University Maurer School of Law, Bloomington, Indiana, April 7-8, 201

Religion, human rights, and surveillance

In this article, I am not addressing populism and freedom of expression per se, i.e. as two issues that I closely focus upon. Rather the perspectives are intertwined in the overall discussions and examples. Surveillance technologies can be used to stimulate populism and limit freedom of expression, as well as they can contribute to the opposite.The outcome does not only depend on the technology and its capacities, but on the persons, citizens, states, religious groups, and companies who use it. After centuries of technological innovations alongside industrialisation, the concept of surveillance has been associated with a Big Brother society, i.e. asymmetrical surveillance by the state or employer to surveil citizens or employees with different tools, visible or invisible. The aims of surveillance are a multitude: protection, security,efficiency, steering of behaviour and opinions, prevention of unwanted actions, et cetera. After the 9/11 terror attack in New York and Washington in 2001, the idea and implementation of surveillance technology has increased unimaginably, in parallel with a political view of the ‘war against terror’, and in parallel with possibilities for advanced technology that has become an essential part of how we, as humans, understand our life as individuals and as communities. One consequence of the paradigm is a certain gaze upon religious communities, where some become more visible than others