Synopsis

Recent advances in laser technology now enable the combination of multiple high-quality lasers into a single high-power beam. This project aims to investigate such 'coherently-combined' laser systems within the context of Earth-to-Space laser transmission. Applications of this technology include space debris tracking, free-space optical communications, and propulsion of light-sails for interstellar travel, such as Breakthrough Starshot.

Research fields

Engineering in Physics;Photonics, Lasers and Nonlinear Optics

Required background

Knowledge in optics (interferometry/lasers) and/or digital signal processing strongly recommended.

Description

The use of beamed energy for the propulsion of light-sail-equipped space probes offers a reusable, scalable and rapid way to explore interplanetary and interstellar space. One of the major challenges in realizing these systems is efficiently delivering huge amounts of optical power from terrestrial sources through a turbulent atmosphere to a light-sail in orbit. 

There are many facets to the challenge of developing laser arrays for the propulsion of interstellar spacecraft. To deliver optical power at the scale required, we have to look at coherently combining multiple lasers - an optical phased array. This involves developing, building and testing measurement schemes that can precisely track and control the optical phase of many individual lasers so they act as one coherent array. 

A bonus feature of an optical phased array is that having multiple lasers allows for manipulation of the wavefront of the combined beam. This can be done by adding phase offsets to individual lasers, allowing it to construct almost arbitrary wavefronts at the output. We can use this to form an adaptive optics (AO) system that actively pre-compensates for any atmospheric turbluence.

By integrating phase measurement, phase control and adaptive optics into one scalable package, this project aims to develop a platform for large scale optical phased arrays - the likes of which are required for programs such as Breakthrough Starshot. Beyond interstellar propulsion, the same technology can be translated for use in applications such as space-debris tracking, free-space optical communications and ranging. The project has a broad scope and can be tailored to focus on theoretical, computational or experimental work towards this ambitious endevour.