Nanoscience USRG – EPSRC Summer Bursaries 2014
June 25, 2014
by Alexander Jantzen
Alexander Jantzen – ‘Enhanced sensitivity Golay cell’
In recent years there has been great advancements in production of Terahertz (THz) emitters, which in turn have lead to a need in developing new reliable, sensitive detection mechanism. Terahertz refers to the part of the electromagnetic spectrum with a frequency of 109 Hz. Specifically THz radiation is consider to be in the region from 0.3 THz to 30 THz, bridging the gap between infrared and microwaves. The most common way of measuring THz radiation is using a time domain spectrometer (TDS) as it has a very high signal-to-noise ratio, however it has to be used as an emitter/receiver package preventing detection of asynchronous THz emission.
Now that the THz region is more easily accessible, part in thanks to the development of the quantum cascade laser (QCL), it is finding its way into an increasingly wide variety of applications. A few examples of this are, non-invasive detection of cancerous cells, material analysis, homeland security, information and communications technology, and more.
The current alternative to a TDS is using a bolometer, however it suffers from difficult operation and is impractical due to it requiring liquid Helium temperatures. Golay cells were forgotten for many years, but recently started to compete with bolometers as they are far more practical, cheaper and are slowly becoming as sensitive in the infrared/THz region.
Picture 1 & 2, THz Time Domain Spectrometer with receiver-transmitter package (left) and a Quantum Cascade Laser with a Golay cell detector (right).
I have just finished my 3rd year of my Masters of Physics with experimental research (MPhys) and I will be spending my summer working on the project of enhancing the sensitivity of a Golay cell through applying physical principles and engineering solutions. A Golay cell is an apparatus based on the simple concept of thermal expansion of a gas caused by THz radiation, whereby a membrane will push outwards. This expansion can be measured by deflecting an optical beam off the membrane, allowing the intensity of THz radiation to be determined. My aim is to finalise a design for a Golay cell allowing us to create them on site. Then, further to this, apply an interferometer to our cells thereby allowing for increased sensitivity of the measurements. Through refining the design and quantising the error sources, the overarching goal for the future will be to make a “Golay Camera”.
Picture 3, Interference pattern from interferometer.
I will continue to work on this project beyond the summer as I intend to use it as my final year, masters research project. During this I expect that an array or a matrix of cells can be used to generate a camera for THz, which currently no company manufacture. This suggests to me that, with a good design, an industrial collaboration could be a very plausible outcome for the final product.