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

In situ characterization of two wireless transmission schemes for ingestible capsules

We report the experimental in situ characterization of 30-40 MHz and 868 MHz wireless transmission schemes for ingestible capsules, in porcine carcasses. This includes a detailed study of the performance of a magnetically coupled near-field very high-frequency (VHF) transmission scheme that requires only one eighth of the volume and one quarter of the power consumption of existing 868-MHz solutions. Our in situ measurements tested the performance of four different capsules specially constructed for this study (two variants of each transmission scheme), in two scenarios. One mimicked the performance of a body-worn receiving coil, while the other allowed the characterization of the direction-dependent signal attenuation due to losses in the surrounding tissue. We found that the magnetically coupled near-field VHF telemetry scheme presents an attractive option for future, miniturized ingestible capsules for medical applications

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

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

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

Hybridization of optical plasmonics with terahertz metamaterials to create multi-spectral filters

Multi-spectral imaging systems typically require the cumbersome integration of disparate filtering materials in order to work simultaneously in multiple spectral regions. We show for the first time how a single nano-patterned metal film can be used to filter multi-spectral content from the visible, near infrared and terahertz bands by hybridizing plasmonics and metamaterials. Plasmonic structures are well-suited to the visible band owing to the resonant dielectric properties of metals, whereas metamaterials are preferable at terahertz frequencies where metal conductivity is high. We present the simulated and experimental characteristics of our new hybrid synthetic multi-spectral material filters and demonstrate the independence of the metamaterial and plasmonic responses with respect to each other

Simplified model of a layer of interconnects under a spiral inductor

An empirical effective medium approximation that provides a homogeneous equivalent for a layer of interconnects un-derneath a spiral inductor is presented. When used as part of a numerical 3D model of the inductor, this approach yields a faster simulation that uses less memory, yet still predicts the quality factor and inductance to within 1%. We expect this technique to find use in the electromagnetic modeling of System-on-Chip

Transmittance of a tunable filter at terahertz frequencies

A metallic photonic crystal filter has been demonstrated at terahertz frequencies, with the passband tunable over the range of 365–386 GHz. Tuning is achieved by a relative lateral shift of two metallic photonic crystal plates. Each plate is comprised of two orthogonal layers of gratings and integral mounting lugs. The plates are micromachined from silicon wafers then coated in gold to provide metallic electromagnetic behavior. An insertion loss of 3–7 dB and Q in the range of 20–30 was achieved. A shift of 140 µm gave a tuning range of 21 GHz, tuning sensitivity of 150 GHz/mm, and a fractional tuning range of 6%

Diode-switched thermal-transfer printed antenna on flexible substrate

We demonstrate that diode-switching can be used to introduce frequency agility into antennas produced by thermal transfer printing. Our particular example is a triangular Sierpinski fractal pattern with two PIN diodes to switch between operation optimised for the 800 MHz UHF band (diodes on) and the 2400 MHz ISM band (diodes off). Our measured results show an improvement in S11 in the UHF band from -2 dB to -28 dB, and from -7 dB to -30 dB at 2400 MHz, when switching the diodes appropriately. The measured bandwidth is 200 (1000) MHz, and the measured directivity is 3.1dB (5.2dB) while the measured gain is -5.2dB (6.7dB) for the diodes on(off)

Novel implementation of the convolution perfectly matched layer in ADI-FDTD method

We present a novel implementation of the convolution perfectly matched layer (CPML) with complex frequency shifted (CFS) parameters in ADI-FDTD. The developed method avoids treating intermediate (half-step) variables as approximate solutions of Maxwell's equations. Our approach to the recursive convolution computation is straightforward to implement and numerical results show that the effectiveness of the developed CPML implementation is almost independent of Courant-Friedrichs-Lewy (CFL) facto