In 2013 the laser manufacturing company Chromacity was incorporated to commercialise tunable femtosecond laser technology from the research group. Scotland's first laser manufacturer to be founded for a number of years, Chromacity has been profitable since it was founded and secured first-round investment in 2015. The company now employs several staff and has customers in the UK, Europe and the US.
In 1997 we demonstrated a new and simple method for measuring ultrashort laser pulses based on two-photon absorption.The corresponding paper and accompanying US patent led to the wholesale adoption of two-photon autocorrelation techniques by the ultrafast laser community, and to a commercial product, the Timewarp autocorrelator – winner of the Laser Focus Commercial Instrumentation Award in 1999.
Today, two-photon autocorrelation is used in nearly every ultrafast laser lab as a simple way measuring laser pulses as short as a few femtoseconds.
Since the late 1990s we have carried out sustained development of the use of infrared femtosecond lasers to probe and image CMOS integrated circuits. This work achieved world-leading optical imaging resolutions (70 nm using a 1530-nm laser) and, as reported in Nature Photonics, was the first to use the vectorial nature of light to substantially surpass the scalar diffraction limit in microscopy.
Working with industrial collaborators DCG Systems and Freescale we developed novel 1.28-µm laser technology which allows femtosecond pulses to be delivered over several metres of optical fibre and then coupled into a circuit using a high-resolution scanning microscope. When infrared femtosecond pulses are injected into a CMOS transistor they perturb its operation, causing it to switch faster or slower, depending on the doping impurity in the junction. This effect can be used in a technique called two-photon absorption LADA (2pLADA) to localize the positions of "bottleneck" transistors, those which limit the speed of a signal along a critical path in a circuit. This work has led to a number of patents and to the adoption of 2pLADA commercially.
The complete and exact measurement of the electric field of femtosecond laser pulses requires more advanced techniques than autocorrelation. In the early 2000s we developed a number of experimental approaches and phase-retrieval algorithms for complete femtosecond pulse characterisation using sonograms (also known as dynamic spectrograms), leading to several well cited papers in this area.
In collaboration with the University of Bath, we carried out some of the earliest work on soliton propagation in solid-core and hollow-core photonic crystal fibre, including one of the earliest observations of the soliton self frequency shift and the delivery of high energy pulses via soliton propagation in a hollow-core fibre.
Working with the National Physical Laboratory we developed a common-path self-referencing interferometer for carrier-envelope offset frequency stabilization with enhanced noise immunity. This technology offered a 10x reduction in noise over the previous embodiments of f-to-2f interferometers and several such interferometers are now incorporated into NPL's frequency comb systems.