Laser Frequency Comb Technology for the Extremely Large Telescope

About the Project

We are seeking to appoint a talented PhD candidate to join the Ultrafast Optics Group at Heriot-Watt by 1 October 2026 and help us to build cutting-edge laser technology for the world’s largest telescope—the ELT—creating ultra-precise “astrocomb” lasers that will enable some of the most exciting science in modern optical astronomy.

Summary

The project concerns the development of new laser technology for the Extremely Large Telescope (ELT), which once completed will be the world's largest telescope. Its massive 39 metre diameter mirror will allow it to collect starlight whose spectra encode the periodic motions of exoplanets, and may even reveal the presence of signatures-of-life chemicals in exoplanet atmospheres.

The Ultrafast Optics Group at Heriot-Watt is part of the UK ELT consortium developing the components for the ANDES high-resolution spectrograph for the ELT. A critical component of ANDES is a "laser astrocomb"— a femtosecond laser that produces a regularly-spaced series of thousands of wavelengths, which can be used like a ruler to provide a highly precise calibration scale for the spectrographs used on the ELT. A general summary of how we use lasers for this purpose can be found in our article in The Conversation magazine.

Laser frequency combs are a special type of laser that produce a spectrum made up of many equally spaced, very sharp spectral lines—like the evenly spaced teeth of a comb. The technology was recognised in the 2005 Nobel Prize in Physics, which was awarded for "contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique".

This is an experimentally-led research project in which we are building and characterising astrocombs—laser frequency combs specially designed for astronomy.

Research activities in more detail

Research will focus on building and characterising astrocombs for three different spectral regions: 400–520 nm; 520–650 nm; and 650–1050 nm. Starting from a primary commercial femtosecond laser, the astrocombs are created using supercontinuum processes in nonlinear components including photonic crystal fibre and PPLN waveguides. These supercontinua are then filtered using Fabry-Perot cavities to increase the comb-mode spacing to a separation that matches the requirements of an astronomical spectrograph.

The development of these technologies requires characterisations of the primary laser comb, the development and implementation of electronic comb stabilization techniques, optical design and spatial / temporal beam modelling, and optical alignment of nonlinear devices, cavities and diagnostics such as wavemeters and spectrographs. Spectral flattening techniques using spatial light modulators are also to be implemented in the system.

An example of a recent milestone in the system development can be found in our 2024 Nature Communications paper.

About you

Suitable applicants will have a first-class undergraduate masters degree (or equivalent) in physics or other relevant discipline. Applicants not meeting this formal criterion but having compensating research experience e.g. in industry, will also be considered.

Candidates will join a diverse team of graduate and post-doctoral researchers. You should have a solid understanding of optics and lasers and have relevant experimental experience, for example through an undergraduate research project or research internship.

While experimentally-led, the project will also include computational components, so experience in scientific programming for data analysis and capture, e.g. using Matlab or Python, is also valuable.

How to apply

Interested candidates should begin by emailing Prof. Derryck Reid (D.T.Reid@hw.ac.uk) to arrange an informal call to discuss the project in more detail. Formal applications must be made through the Heriot-Watt on-line application system, https://www.hw.ac.uk/study/apply/uk/postgraduate.htm.

Start date

The project will start in October 2026.

Funding Notes

Full funding, covering fees and stipend (in line with UKRI values), is only available for applicants who are UK nationals; have settled status; have pre-settled status (meeting residency requirements); have indefinite leave to remain or enter, or are otherwise eligible for Home fee status.