Chris Mann

A low-cost fabrication technique for symmetrical and asymmetrical layer-by-layer photonic crystals at submillimeter-wave frequencies

This paper presents a rapid, versatile, and practical technique for the manufacture of layer-by-layer photonic crystals in the millimeter- and submillimeter-wave regions. Mechanical machining is used to derive a rugged layer-by-layer structure from high-resistivity silicon wafers. Unlike traditional anisotropic etching techniques, this method does not rely on any particular crystal orientation of the substrate and allows greater flexibility in the photonic crystal design. Automatic alignment of alternating layers is achieved via careful placement of the separation cuts. Using this ability, two configurations of photonic crystals are realized and their RF characteristics are measured and presented. Firstly, a symmetrical photonic crystal is studied as an initial demonstration of the technique. This is followed by an asymmetrical example, where a different frequency response is observed for the two orthogonal polarizations of the incident radiation. Two measurement techniques are used to characterize the photonic crystals and the merits of each are discussed. Theoretical predictions are seen to agree well with the measured behavior.

Microfabrication of 3D terahertz circuitry

Advances in micro-fabrication techniques combined with accurate simulation tools has provided the means for the realisation of complex terahertz circuitry. Silicon micro-machining provides the way forward to fabricate accurate rugged structures. Multi-level deep reactive ion etching can be used to replace traditional machining methods achieving smaller feature size, improved surface finish and greater freedom in circuit layout. Photonic Bandgap waveguides enable three dimensional arrangements of active devices antennae and filters, and removes the requirement for metallisation of adjoining surfaces. This paper describes some of the state of the art terahertz circuit design and realisation using these techniques.

(Sub)mm-wave components and subsystems based on PBG technology

Photonic band gap (PBG) materials present some interesting properties that may overcome some of the problems of conventional technologies. In particular, PBG architecture provides a practical method for the assembly of RF circuitry having three-dimensional properties. This paper presents some (sub)mm-wave components based on this technology. PBG dipole antennas and PBG waveguides have been studied. In addition, PBG crystals and active devices have been combined for the first time resulting in a PBG mixer. First results suggest that circuits implementing PBG technology can compete with conventional waveguide technology. A PBG based subharmonic mixer operating around 250 GHz exhibits a double sideband noise temperature of 3800 K.

A 250 GHz Subharmonic Mixer Design Using EBG Technology

The design, manufacture and characterization of a sub-harmonic mixer operating in the millimeter wavelength range is described. The mixer combines for the first time electromagnetic band gap (EBG) technology (which improves the radiation features of the dipole antenna used to couple radiation to the mixer), with conventional local oscillator (LO) waveguide circuitry. The mixer is designed to operate in an RF frequency band around 250 GHz when supplied with a LO frequency between 115 and 135 GHz. The fixed IF frequency spans 2.5-3.5 GHz. Performance predictions were made using a combination of the finite elements (FE) method to compute the embedding impedance of the diodes and the harmonic balance analysis (HBA) to predict the noise temperature. A prototype mixer has been fabricated and tested. Best mixer performance (double side band (DSB) mixer noise temperature and conversion loss of 3000 K and 11.5 dB, respectively) was measured with a LO power level of about 5 mW. Good agreement is observed with the predicted performance.

A high power 270 GHz frequency tripler featuring a Schottky diode parallel pair

A high output power millimetre wave frequency tripler is reported. Important features of the diode mount include a planar waveguide probe which facilitates the parallel combination of two Schottky varactor diodes and provides them with a more ideal embedding impedance. This approach allows for higher power production and handling ability than a similar device using a single diode. Maximum output power at 271 GHz is 15 mW with a flange to flange efficiency of /spl ap/5%.

Practical Challenges for the Commercialisation of Terahertz Electronics

The main technology driver for terahertz detection has been used for radio astronomy. The drive for absolute noise performance has required cooled detection techniques. Commercially such an approach is complex, costly and limits usability. For commercial applications a is preferred but the associated costs have been high. A description will be given of the major challenges that have been undertaken to realise a commercial electronic terahertz product. An outline of the product and examples of typical output will be provided.