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Research

Our research concerns the development of novel ultrafast lasers for applications in spectroscopy, metrology and microscopy.

Ultrafast Optical Parametric Oscillators (OPOs)

Unlike laser sources, whose wavelengths are defined by the naturally occurring electronic transitions of the active medium, OPOs provide femtosecond pulses tunable across a massive wavelength range, constrained only by the transmission properties of the nonlinear gain crystal.  We have demonstrated femtsecond pulses directly from OPOs from 800 nm 12 µm.  Heriot-Watt OPO technology has also been commercialised by the spin-out company Chromacity Ltd..

Optical Frequency Combs

Frequency combs are the world’s most precise laser sources, with intrinsic noise measured at the 10-19 level, and celebrated in the 2005 Nobel prize to Jan Hall and Ted Haensch for their early work in developing this technology. In 2007 we were the first group to demonstrate a femtosecond OPO frequency comb.  An important application of frequency combs is in optical metrology (the measurement of light). The combination of wide wavelength coverage with ultra-precise control of the comb-teeth positions makes OPO combs extremely versatile metrology devices.  Under two EPSRC grants we are developing optical frequency combs for quantum timekeeping and for precision manufacturing.

Astrocombs

An important application of laser frequency combs is in astronomy. LFCs are an enabling technology needed to address STFC's Roadmap Challenges, such as the discovery and characterisation of Earth-like planets around solar-like stars and better understanding how the universe is evolving. Modern telescopes are equipped with high resolution spectrographs, instruments which can measure the colour of starlight very precisely, and can sense the tiny changes which are caused by an orbiting planet.  Laser frequency combs provide a "ruler in frequency" which can be used by astronomers to accurately calibrate such measurements, allowing fundamental theories to be tested and the experimental error in observations to be reduced considerably. Under two grants from STFC we are developing femtosecond OPOs as frequency combs for astronomy, supporting the Phase A study of the "UK Programme for the European Extremely Large Telescope," an international consortium in which Heriot-Watt is a partner.  

Mid-Infrared Standoff Chemical Detection and Environmental Sensing

Working with Dstl and NPL we have developed sources for the detection of gases and liquids which pose a threat to either human health or to the environment.  The techniques developed make use of mid-infrared optical parametric oscillators as powerful broadband light sources which can be used to illuminate chemicals and observe their unique absorption spectra, which reveals details of the chemical bonds and groups presents.  We have used this technique to detect hazardous liquid chemicals over several metres range, and to sensitively detect greenhouse gases as high acquisition rates using the dual-comb spectroscopy method.

Nonlinear Microscopy for Failure Analysis of Semiconductor Devices

Modern integrated circuits possess components with feature sizes approaching 10 nm, etched in a thin silicon substrate and covered by many layers of microscopic metal wiring.  Physical access to these components is nearly impossible, but infrared laser light introduced through the silicon substrate can reach the device layer and be used to image and probe the circuit.  Working with DCG Systems and Freescale we have 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.

Research Projects

Frequency Comb Enabled Metrology for Manufacturing

This proposal aims to transition today's highest precision laser technology -- optical frequency combs -- from the lab to the factory, establishing the technique of dual-comb distance metrology as an enabling technology for manufacturing the next generation of precision-engineered products, whose functionality relies on micro-/ nanoscale accuracy.  More...
 
     
 




Remote Sensing of Greenhouse Gases With Asynchronous Femtosecond OPOs

Optical remote sensing is a key tool for GHG measurements across scientific and industrial applications. However, significant limitations exist in current technologies in terms of their bandwidth, resolution and range. Asynchronous femtosecond optical parametric oscillators (OPOs) could combine the spatial coherence of a laser with the bandwidth of a thermal source to provide high resolution measurements of multiple gases over long ranges. More...
 
   
 



METROCOMB femtosecond comb optical parametric oscillators for high resolution spectroscopy in the mid-infrared

The research necessary to extend the application areas of femtosecond frequency combs through the development of compact, robust, low-cost, commercially-exploitable sources is now possible; taking advantage of the fact that ultrafast laser pulses of femtosecond widths, separated by nanoseconds, manifest themselves as a phase-coherent comb of frequencies spread over a wide spectral band. More...
 
   
           

Precision Astronomical Spectrographs using Single-Mode Photonic Technologies

This STFC Consortium Grant thus brings together experts from the fields of photonics and astronomical instrumentation, with one clear and ambitious overall objective - to establish whether laser frequency combs and photonic-lanterns can facilitate astronomical spectrographs with unprecedented performance. More...
 
   



Ultra-Broadband Laser Frequency Combs for Precision Spectrograph Calibration

The astronomy community faces a critical problem in how to provide perpetual online calibration of new ultra-high-resolution spectrographs, which play a central role in answering today's "big questions" such as the discovery of extra-solar Earth-like planets, and the variation of "fundamental" constants. More...
 
   



Stand off laser identification of chemical contamination (SLICC)

This project will work across multiple strands of technology at different maturity levels to derisk future military systems needed to rapidly and accurately identify chemical contamination. It will encompass a wide range of topics from fundamental research through to sub-system testing and assessment. More...
 
 

HIRES Phase A study 2016+

This Phase A extension will be used to complete a topic-by-topic design study identifying a technical pathway allowing a degenerate optical parametric oscillator (OPO) frequency comb to meet the E-ELT science requirements. More...
 
   



Two-Photon LADA for Defect Localization in Integrated Circuits

We propose a two-photon Laser Assisted Device Alteration (2pLADA) technique for fault localization using a 1250nm femtosecond laser and a high numerical aperture (NA) Solid Immersion Lens (SIL) to achieve the 80nm lateral resolution metric demanded by the 11nm node. More...
 
 
   



Broad-Range Detection of Hazardous Aerosols in the 5–12-µm Region

We propose to develop already proven concepts to a higher TRL by: (a) extending the wavelength into the 5– 12-μm band; (b) further improving the sensitivity and selectivity of the technique; and (optionally), (c) developing, with commercial laser engineering support, a fieldable platform which can be evaluated at Dstl. More...
 
 



Compact Visible Frequency Combs: The Missing Link in a Vision of Pervasive Quantum Timekeeping

By leveraging advances in ultrafast lasers and integrated nonlinear photonic devices, this project targets the development of a disruptive laser-comb technology, compatible with visible clock transitions in new ion-based time standards, and with a scale suitable for integrating into quantum timekeeping devices needed by sectors from security and defence to geodesy and finance. The project is shaped by technical and financial support from leading industrial and academic partners. More...