The UK-based team has exceeded a 1 Watt output power from a quantum cascade terahertz laser, doubling the landmarks set by the Massachusetts Institute of Technology (MIT) and a team from Vienna last year.
“Although it is possible to build large instruments that generate powerful beams of terahertz radiation, these instruments are only useful for a limited set of applications. We need terahertz lasers that not only offer high power but are also portable and low cost,” said Professor Edmund Linfield, Professor of Terahertz Electronics in the University’s School of Electronic and Electrical Engineering.
The quantum cascade terahertz lasers being developed by Leeds are only a few square millimetres in size.
Terahertz waves, which lie in the part of the electromagnetic spectrum between infrared and microwaves, can penetrate materials that block visible light and have a wide range of possible uses including chemical analysis, security scanning, medical imaging, and telecommunications.
Widely publicised potential applications include monitoring pharmaceutical products, the remote sensing of chemical signatures of explosives in unopened envelopes, and the non-invasive detection of cancers in the human body. However, one of the main challenges for scientists and engineers is making the lasers powerful and compact enough to be useful.
In October 2013, Vienna University of Technology reported an output of 0.47 Watt from a single laser facet, nearly double the output power reported by the MIT team. The Leeds group has now achieved an output of more than 1 Watt from a single laser facet.
“The process of making these lasers is extraordinarily delicate. Layers of different semiconductors such as gallium arsenide are built up one atomic monolayer at a time," said Professor Linfield. "We control the thickness and composition of each individual layer very accurately and build up a semiconductor material of between typically 1,000 and 2,000 layers. The record power of our new laser is due to the expertise that we have developed at Leeds in fabricating these layered semiconductors, together with our ability to engineer these materials subsequently into suitable and powerful laser devices.”
The department has been focusing heavily on terahetz technologies, setting up a dedicated Terahertz lab in October 2012 with support from Agilent Technologies, making it the first Agilent-equipped terahertz measurement laboratory in Europe.
The lab was set up in memory of Professor Roger Pollard, former Dean of Engineering at the University of Leeds who passed away at the end of 2011. "Roger Pollard had a long history of collaboration with Agilent, spanning more than 30 years, and held the Agilent Technologies chair in high-frequency measurements," said Professor Peter Jimack, current dean.
The PNA THz network analyzer allows university staff to perform on-wafer terahertz measurements of transistors, THz biosensors, magnetic storage elements, THz spin-switches and novel acoustoelectric devices. It will also be used to characterize THz passive components such as filters, waveguides, fibers and antennas.
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