Abstract

Research utilising the terahertz spectral region (0.1 – 10 THz, 3000 – 30 µm, 0.4 – 40 meV) is both diverse and rapidly advancing, with applications in spectroscopy, astronomy, security imaging, and pharmaceuticals analysis. This frequency range is of fundamental interest, corresponding to low energy electronic excitations and vibrational modes in solids, as well as vibrational and rotational transitions in molecules. However, the ability to investigate the THz physics of samples at cryogenic temperatures (4 K and below) has to date been hampered by a lack of suitable systems capable of addressing the considerable optical, mechanical and thermal challenges involved. This talk will outline work towards the development of a near-field nanoscopy system capable of imaging semiconductor samples at THz energies and at temperatures of 4 K and below, with a spatial resolution better than 100 nm (~λ/1000), whilst simultaneously obtaining topographic information. To achieve this aim, research into two requisite areas will be discussed – waveguided radiation delivery for low temperature cryostats, along with the demonstration of a room temperature THz near-field microscope utilising a quantum cascade laser as both source and detector. Finally, some future research directions resulting from such a technology will be discussed, including a selection of the wealth of semiconductor systems to be studied, such as single photon detectors and quantum dot electron pumps.