Calculated and measured transmittance of a tunable metallic photonic crystal filter for terahertz frequencies

A tunable metallic photonic crystal filter with a mechanical tuning mechanism is demonstrated. The performance is predicted with rigorous full-vector electromagnetic simulations (finite-difference time domain). A prototype has been built and characterized in the W band (70–110 GHz) using a vector network analyzer configured for free-space measurement of S parameters. The measured filter's passband has a quality factor of 11, a tuning range of 3.5 GHz, and insertion loss of only 1.1–1.7 dB. Device fabrication is straightforward, yielding an inexpensive, robust and compact tunable filter

Tunable photonic crystal filter for terahertz frequency applications

In this Paper we investigate a tunable metallic photonic crystal filter with a novel mechanical tuning method, suitable for use in terahertz frequency applications. Tuning has been demonstrated in a micrometer-driven prototype at 70 - 110 GHz in accordance with rigorous full-vector electromagnetic simulations (finite-difference time-domain). The measured pass band has a Q of 11 and can be tuned over a 3.5 GHz range. The insertion loss is only 1.1 to 1.7 dB, while the stop band attenuation is >10 dB. The filter has the advantages of inexpensive, robust and compact construction and tunable operation that readily scales to any desired terahertz frequency

Variable polarisation compensator using artificial dielectrics for millimetre and submillimetre waves

A variable polarisation compensator has been designed and demonstrated experimentally at 100 GHz. The device uses two silicon plates with interlocking artificial dielectric surfaces to produce a birefringence that varies with the separation distance. The experimental results indicate a maximum differential phase-shift of 74°, and show good agreement with computer simulation

Artificial dielectric devices for variable polarization compensation at millimeter and submillimeter wavelengths

Variable polarization compensation has been demonstrated at 100 GHz. The device consists of two interlocking V-groove artificial dielectric gratings that produce a birefringence that varies with the separation distance. A maximum retardance of 74/spl deg/ has been obtained experimentally in a silicon device, in good agreement with rigorous coupled-wave computer simulations. Further simulations predict that adding quarter wave dielectric antireflection (AR) coatings to the outer surfaces of the device can reduce the insertion loss to below 4 dB. The use of rectangular grooved gratings provides increased retardance and reduced loss. It is predicted that a coupled device with rectangular grooved gratings will be capable of maximum retardance in excess of 180/spl deg/, with low insertion loss (<0.6 dB). The sensitivity of the wave retardation as a function of mechanical separation has a peak value of 485/spl deg//mm. The design and micromachining fabrication techniques scale for operation at submillimeter wavelengths

Teaching integrated circuit and semiconductor device design in New Zealand: the University of Canterbury approach

Teaching the practical aspects of device and chip design in New Zealand presents many problems, including high manufacturing costs, long lead times, and the lack of local industry strength. Nonetheless, it is possible to overcome these issues. This paper describes the courses in these areas at the University of Canterbury, including a practical IC design project that has been running successfully for the past four years. The IC design project takes final year students through a full custom design using modern design tools and fabrication processes. The design is quite straightforward — a 4-bit arithmetic logic unit — but it emphasises the importance of design, simulation and testing. The final circuits contain a few hundred transistors, so good practice is essential. Twelve designs are integrated on to a single chip to keep costs down, and individual designs are addressed via multiplexers. The designs are fabricated using a 0.5 micron process, accessed through a multi-project vendor (MOSIS). Getting chips back from a manufacturer is significantly more motivating for the students than just performing a paper design

Spatializing the Ecological Leviathan: Territorial Strategies and the Production of Regional Natures

This paper explores a dual absence – the absence of the state within contemporary geographical analyses of nature; and the absence of nature within contemporary explorations of state power. We argue that the modern state continues to play a crucial role in framing social interactions with nature, while nature is still vital to states within their realization of different forms of material and ideological power. In order to reconnect analyses of the state and nature, this paper combines work on the production of nature and state strategy with Lefebvre’s recently translated writings on state space and territory. By focusing on the production of territory (or state space), we explore the interaction of the state and nature in the context of the political management of social and ecological space. We unravel the spatial entanglements of the state and nature through an analysis of the British state’s territorial strategies within the West Midlands region. By considering three key historical periods within the history of the West Mid-lands we reveal how the emergence of the regional space called the West Midlands is a product of the ongoing spatial dialectics of state and nature therein

Vulnerability and its discontents: the past, present, and future of climate change vulnerability research

The concept of vulnerability is well established in the climate change literature, underpinning significant research effort. The ability of vulnerability research to capture the complexities of climate-society dynamics has been increasingly questioned, however. In this paper, we identify, characterize, and evaluate concerns over the use of vulnerability approaches in the climate change field based on a review of peer-reviewed articles published since 1990 (n = 587). Seven concerns are identified: neglect of social drivers, promotion of a static understanding of human-environment interactions, vagueness about the concept of vulnerability, neglect of cross-scale interactions, passive and negative framing, limited influence on decision-making, and limited collaboration across disciplines. Examining each concern against trends in the literature, we find some of these concerns weakly justified, but others pose valid challenges to vulnerability research. Efforts to revitalize vulnerability research are needed, with priority areas including developing the next generation of empirical studies, catalyzing collaboration across disciplines to leverage and build on the strengths of divergent intellectual traditions involved in vulnerability research, and linking research to the practical realities of decision-making

Enhanced optical transmission through planar metallic films via excitation of surface plasmons

©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.A study on extraordinary optical transmission through planar metallic films closely coupled to periodic sub-wavelength structures is presented. The measured spectral positions of transmission maxima match well with the surface plasmon polariton (SPP) dispersion relations. The experimental results are further supported by rigorous coupled wave analysis (RCWA) simulations. The exceptional transmission is a result of coupling between the localized surface plasmon (LSP) mode existing in periodic sub-wavelength structures and the SPP modes on the planar metal films

Surface-plasmon-enhanced light transmission through planar metallic films

We show experimental results for the optical transmission of planar metallic films closely coupled to periodic subwavelength structures; exceptionally high transmission levels (up to 39%) are measured for these otherwise-opaque films. The measured dispersion of the transmission maxima agrees well with the theoretical dispersion of surface plasmon polariton (SPP) modes on a planar metal film, which strongly suggests that the excitation of these SPP modes is responsible for the exceptional transmission features. This is further supported by rigorous coupled wave analysis simulations. The overall transmission is a result of the coupling between the incident light and the SPP modes, as well as the localized surface plasmon modes within the structure