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EPSRC Reference: EP/C534263/1
Title: ARTIFICIAL MATERIALS FOR TERAHERTZ FREQUENCY APPLICATIONS
Principal Investigator: Chamberlain, Professor JM
Other Investigators:
Wood, Professor D Petty, Professor MC Brand, Dr S
Abram, Professor R
Researcher Co-Investigators:
Dr M Kaliteevski
Project Partners:
Department: Physics
Organisation: Durham, University of
Scheme: Standard Research (Pre-FEC)
Starts: 01 August 2005 Ends: 31 July 2008 Value (£): 366,724
EPSRC Research Topic Classifications:
Materials Processing RF & Microwave Technology
EPSRC Industrial Sector Classifications:
Electronics
Related Grants:
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Summary on Grant Application Form
Over a hundred years ago scientists realised that visible light was part of the electromagnetic spectrum: light is characterised by a wavelength (like the distance between ripples on a pond), or by frequency (number of ripples going by in a second). The colours in the rainbow correspond to various wavelengths around a half millionth of a metre. In time, other types of electromagnetic radiation (emr) were recognized, e.g.: infrared (wavelength around a millionth of a metre) and microwaves (wavelength a centimetre or so). It was recognized that emr consists of both electric and magnetic fields moving along at a characteristic speed. A source of emr could be, e.g., a light bulb, or a radio antenna . Normally, we are not interested in getting close to a source of emr, but in the far-field, as it is called, where energy is carried away. Recently, it has been realised that there is a great deal happening close to the source, i.e. in the near-field. This Proposal deals with specially-made devices that can manipulate this near-field in a certain wavelength range. We plan to use these new devices to make better imaging systems that can direct this emr into places such as the inside of the human body, where it might be used for cancer detection or to sense explosives or drugs on people through clothes. We might also want to make a special microscope for this range to look at single cells. This wavelength range lies between radio and infrared, and corresponds to wavelengths about one millimetre to about one thirtieth of a millimetre. It is also known as the Terahertz (THz) range, because the frequency of the radiation is one million million times a second. Amazingly, we are only just beginning to develop efficient tools to create and detect his radiation - more than a century after the discovery of radio. This radiation can sense cancers and explosives because molecules wobble, vibrate and rotate at THz frequencies.Everyone knows that when you see a stick in water it seems to be bent. In the 17th century, Thomas Harriot produced a law to describe this, which was stolen by the Dutchman Willibrod Snell. It turns out that what is important is the refractive index : this says how fast light (or any emr) can travel in a material. It was later realised that the refractive index was related to two further very important quantities, known as the permittvity and the permeability. These quantities deal with the electric and magnetic field that go to make up emr. Regrettably, in normal materials the numerical values of all of these quantities (refractive index, permeability , permittivity) are provided by the management - there is no possibility of manipulating them, you just have to design equipment to live with these given quantities. Recently, it was discovered that you can make artificial materials, where these quantities can be designed by arranging (for example) that the emr passes through thin metal wires of a certain size and separation. These quantities can even be negative. Strangely, in some of these materials, Snell's ( really Harriot's) law is broken and light is bent in the wrong way. To explain this, you use the near-field concepts mentioned above. Devices based on this could help us make a THz medical endoscope. Also, by making very small holes in semiconductors we can (amazingly) increase the amount of THz that passes through them, perhaps helping us make a THz microscope to view individual cells vibrating or groups of proteins changing shape. We plan to use theory methods (that we have used before), special techniques that come from the semiconductor industry, and advanced THz measurement systems to design, build and test these artificial materials. We will measure their refractive index, their absorption and how well the devices cope with very short pulses of THz. We plan to use this information to help us design-- -- ~~ nrta of practical applications.
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