High-power optical phased arrays for space debris tracking and manoeuvring

The performance of existing ground based space debris laser ranging systems can be improved by directing more light onto space debris targets using an optical phased array (OPA). Furthermore, if the power delivered to target is sufficiently high then these systems may also permit remote manoeuvring of space debris via photon radiation pressure and/or ablation. In contrast to incoherent laser combination, an OPA actively controls the relative phase of multiple lasers, forming a contiguous and coherent optical wave front in the far field. Optical phased arrays are therefore able to support higher total delivery of power to a point in the far field beyond the limits of conventional lasers, without significant penalty on beam quality and cost. We present a scalable OPA architecture that can support high optical powers (>1 kW), and which has been designed to improve the sensitivity of an existing ground-based space debris tracking system in Australia. It is also intended to eventually support the remote manoeuvring of space debris. The ability to independently control the phase of each emitter in the array is enabled using digitally enhanced interferometry. A key feature of our approach is internal sensing, where we derive all control signals from the small fraction of light reflected back into the fibre at the output of the OPA. A proof-of-concept system has recently been tested in the lab, demonstrating excellent coherence in the far-field and quadratic scaling of intensity of the central interference lobe.