Array tilt in the atmosphere and its effect on optical phased array performance.

This paper investigates atmospheric array tilt and its effect on target-in-the-loop optical phased array (OPA) performance. Assuming a direct-solve, piston-only-phase-compensation OPA, two expressions for the atmospheric array tilt variance are derived using Mellin transform techniques. The first-the "full" array tilt variance-is germane when the OPA is sensitive to atmospheric tilt and is shown to significantly impact OPA target-plane intensity. The second-the Zernike-tilt-removed array tilt variance-is relevant when a separate system compensates for atmospheric tilt (the more likely scenario) and is shown to negligibly affect OPA performance. To show how atmospheric array tilt errors affect target-plane intensity, moments of the far-zone (or focused) array intensity, as functions of the array tilt variance, are derived and discussed. Lastly, Monte Carlo simulation results are presented to validate the theoretical array tilt variance expressions.