Optical Phased Arrays for Interstellar Propulsion

An artist’s impression of the Breakthrough Starshot light-sail space probe being accelerated away from Earth by the ground based high-power optical phased array.

The Breakthrough Starshot program is an endeavour proposed by the Breakthrough Initiatives to open up humanity to interstellar exploration. The intended target for the project is the Alpha Centauri system which is to be explored using light-sail endowed space probes launched from Earth orbit. To achieve a transit time of approximately 30 years, the probes are to be illuminated using a ground-based laser array to facilitate acceleration to approximately 20% of the speed of light. The required optical power, beam pointing and atmospheric correction capabilities for this application necessitates the use of an optical phased array with an unprecedented number of emitters and total emitted power. 

Optical phased arrays are complex optical systems that enable the coherent combination of multiple separate optical sources into one directed output. When stabilised, the array act as a single unit with a synthetic aperture the size of the entire array, instead of its constituent emitters. In this state, an optical phased array is able to focus optical power into a central peak and by modulating the output phase of individual emitters within an array, arbitrary wavefronts can be synthesised to enable beam-steering and exotic spatial mode shapes. 

Led by members of the Applied Metrology Laboratory, in collaboration with other members within the Centre for Gravitational Astrophysics (CGA) and the Research School of Astronomy and Astrophysics (RSAA), we develop methods for achieving the necessary requirements for the Breakthrough Starshot optical phased array. Building on initial design work done within CGA, the team is expanding its collaboration to develop the necessary underpinning subsystems for the array design including novel methods for the combination of multiple optical phased arrays, and integrated atmospheric sensing and correction. 

Developing these systems requires a truly multi-disciplinary team including insight into interferometric sensing, control systems, high-power laser design, optical fibre component manufacture and digital signal processing to name a few. While the core team resides within the ANU, the team actively seek out expertise and new collaborations with external partners for the Starshot program, and other applications of modularised optical phased arrays including free-space optical communications and space debris tracking. 

 

Contacts: Dr Chathura Bandutunga, Paul Sibley, Prof. Michael Ireland (RSAA), Prof. Jong Chow 

Updated:  2 July 2021/Responsible Officer:  Science Web/Page Contact:  Science Web