On-chip THz Systems

A variety of novel on-chip terahertz systems have been developed with the aim of advancing current on-chip spectroscopic techniques. A novel methodology for the fabrication and positioning of isolated regions of photoconductive LT-GaAs thin film has been developed, allowing generation and detection of THz signals in-plane with a microstrip transmission line device. Devices with bandwidths in excess of 1.2 THz have been demonstrated. The introduction of novel, THz frequency passive resonator elements, in the form of quarter-wave band stop filters, into a transmission line device allowed measurements of the properties of overlaid dielectric films by monitoring of the resonant shift. Cascading multiple resonators along a single interconnect allowed simultaneous measurements to be performed at isolated frequencies at discrete locations on a single device. The first full characterisation of the resonant shift as a function of load thickness for a THz filter is performed, with measurements obtained in excellent agreement with subsequent free space studies, whilst requiring a 10' reduction in sample volume. Design modifications provided ultrahigh spectroscopic resolution in the terahertz range of <2 GHz, allowing the measurement of overlaid films of DNA in single and double stranded form down to quantities of 0.211 femtomoles, almost double the sensitivity, in terms of average relative resonant shift per base pair, when compared to literature values. The active region of the devices designed for this work is N 123 times less than existing topologies and therefore represents an increase in resonant shift per unit active area of two orders of magnitude.