Experimental demonstration of a simple free-space loss model for diffuse reflections in guided-mode LiDAR

The growing use of photonic integrated circuits in light detection and ranging (LiDAR) sensors has made the speckle and phase distribution of the reflected light relevant for coupling into the guided modes of these systems. We adopt the use of a simplified diffuse surface model to show the average coupling efficiency of reflected speckle into guided modes can be predicted from the optical intensity at the target. For the first time, we provide experimental results to show that this relationship is valid for predicting free-space loss as a function of range. We intend to aid optics design for integrated photonic LiDAR systems, providing a simple and accurate model to predict the free-space loss from a representative target at all distances.