Optical phased arrays are a technology that can improve the useful capabilities of lasers by controlling the relative optical phase of an array of emitting apertures. An optical phased array can coherently combine each emitter to increase optical intensity or arbitrarily shape the outgoing wavefront. This allows output power greater than the typical thermal limit of any individual laser, with the addition of rapid beam pointing and the potential to perform adaptive optics to correct for atmospheric turbulence. Taking full advantage of the potential capabilities of optical phased arrays requires a large number of emitters, typically the more the better.
The research presented investigates the detailed scaling behaviour of an enabling technique, Digitally Enhanced Heterodyne Interferometry, which allows simultaneous measurement of multiple optical phase signals. A combination of experimental, simulation and analytical work has been used predict and improve the performance of the technique, with a particular focus on optical phased arrays.
This research leads to recent work designing a ground-to-space optical phased array to act as the “photon engine” component of the Breakthrough Starshot program. This program is researching the technology needed use photon pressure to propel a sailcraft to Alpha Centauri at 20% of the speed of light, far beyond the capabilities of existing laser systems. A new system to link multiple optical phased arrays is outlined in this presentation, addressing how 100 million lasers might be coherently combined. Also included is how this array can be used to measure and correct for atmospheric turbulence in the context of a ground-to-space laser transmission.
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