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

History, Sociology, Modernity : How Connect?

Special Issue on 'The State of Scottish History: Past, Present and Future'Peer reviewedPublisher PD

Visibility and Invisibility in Art and Craft

The visibility and invisibility or censorship of art and craft is determined by individual and group ontologies. Their production has often been constricted and/or defined by gender, class, culture, race, religion, and politics. In this paper, I am concerned with the visibility of varieties of art, design, and craft. I will examine censorship based on three criteria; gender, culture, and class, with the censorship of artwork because of gender being the dominant theme