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

Tapered photonic crystal microcavities embedded in photonic wire waveguides with large resonance quality-factor and high transmission

We present the design, fabrication, and characterization of a microcavity that exhibits simultaneously high transmission and large resonance quality-factor (Q-factor). This microcavity is formed by a single-row photonic crystal (PhC) embedded in a 500-nm-wide photonic wire waveguide - and is based on silicon-on-insulator. A normalized transmission of 85%, together with a Q-factor of 18 500, have been achieved experimentally through the use of carefully designed tapering on both sides of each of the hole-type PhC mirrors that form the microcavity. We have also demonstrated reasonably accurate control of the cavity resonance frequency. Simulation of the device using a three-dimensional finite-difference time-domain approach shows good agreement with the experimental results

Focused Ion Beam Milling and Deposition of Tungsten Contacts on Exfoliated Graphene for Electronic Device Applications

We demonstrate a rapid-prototyping method for the fabrication of electrical structures from exfoliated graphene using focused ion beam (FIB) assisted deposition of tungsten and milling. Alignment accuracies of less than 250 nm are achieved without imaging of the graphene using the FIB beam. Parameters for the FIB assisted deposition on graphene have to be controlled exactly to avoid damage to the underlying graphene. Measured channel resistance of 58 k? shows a good electrical contact between deposited tungsten and graphene

Transmission of PhC coupled-resonator waveguide (PhCCRW) structure enhanced via mode matching

A method for increasing the coupling efficiency between ridge optical waveguides and PhCCRWs is described. This increase is achieved via W1 channel waveguide sections, formed within a two-dimensional triangular lattice photonic crystal using mode-matching. The mode-matching is achieved by low quality-factor modified cavities added to both the input and output ports of the PhCCRW. A three dimensional finite-difference time-domain method has been used to simulate light propagation through the modified PhCCRW. We have fabricated PhCCRWs working at 1.5µm in silicon-on-insulator material. Measurements and simulations show that the overall transmission is improved by a factor of two

Characterisation at infrared wavelengths of metamaterials formed by thin-film metallic split-ring resonator arrays on silicon

The infrared reflectance spectra at normal incidence for split-ring resonator arrays fabricated in thin films of three different metals on a silicon substrate are reported. The results are compared with a finite difference time domain simulation of the structures and a simple and novel equivalent-circuit method for the calculation of the first and second resonant wavelengths

Large area plasma-enhanced chemical vapor deposition of nanocrystalline graphite on insulator for electronic device application

This paper reports on large area plasma-enhanced chemical vapor deposition (PECVD) of nanocrystalline graphite (NCG) on thermally grown SiO2 wafer, quartz and sapphire substrates. Grown films are evaluated using Raman spectroscopy, ellipsometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Electrical characterization and optical transmission measurementsindicate promising properties of this material for use as transparent electrodes and for electronic device application. A plasma-based etch process for NCG has been developed

Improved silicon quantum dots single electron transfer operation with hydrogen silsesquioxane resist technology

Hydrogen silsesquioxane (HSQ) is a high resolution electron beam resist that offers a high etch resistance and small line edge roughness. In our previous work, we showed that by using this resist we can fabricate very high density double quantum dot (QD) single electron transistors on silicon-on-insulator (SOI) substrates for applications in quantum information processing. We observed that 80% of 144 fabricated devices had dimensional variations of ±5 nm with a standard deviation of 3.4 nm. Here, we report on the functionality of our Si QD devices through electrical measurements and further HSQ process optimisations, which improve the effective side gates control on single electron operation

Design and fabrication of densely integrated silicon quantum dots using a VLSI compatible hydrogen silsesquioxane electron beam lithography process

Hydrogen silsesquioxane (HSQ) is a high resolution negative-tone electron beam resist allowing for direct transfer of nanostructures into silicon-on-insulator. Using this resist for electron beam lithography, we fabricate high density lithographically defined Silicon double quantum dot (QD) transistors. We show that our approach is compatible with very large scale integration, allowing for parallel fabrication of up to 144 scalable devices. HSQ process optimisation allowed for realisation of reproducible QD dimensions of 50 nm and tunnel junction down to 25 nm. We observed that 80% of the fabricated devices had dimensional variations of less than 5 nm. These are the smallest high density double QD transistors achieved to date. Single electron simulations combined with preliminary electrical characterisations justify the reliability of our device and process