Recent work at the U.S. Naval Research Laboratory studied atmospheric turbulence on dynamic links with the goal of developing an optical anemometer and turbulence characterization system for unmanned aerial vehicle (UAV) applications. Providing information on the degree of atmospheric turbulence, as well as wind information and scintillation, in a low size, weight and power (SWaP) system is key for the design of a system that is also capable of adapting quickly to changes in atmospheric conditions. The envisioned system consists of a bi-static dynamic link between a transmitter (Tx) and a receiver (Rx), relying on a small UAV. In a dynamic link, the propagation distance between the Tx/Rx changes rapidly. Due to SWaP constraints, a monostatic system is challenging for such configurations, so we explored a system in which the Tx/Rx is co-located on a mobile platform (UAV), which has a mounted retroreflector. Beam divergence control is key in such a system, both for finding the UAV (increased beam divergence at the Tx) and for signal optimization at the Rx. This led us to the concept of using adaptive/active elements to control the divergence at the Tx but also to the implementation of an adaptive/active retroreflector in which the return beam divergence can be controlled in order to optimize the signal at the Rx. This paper presents the design, fabrication and characterization of a low SWaP adaptive retroreflector.

Modeling and simulating atmospheric turbulence in a controlled environment have been a focus of interest for scientists for decades. The development of new technologies allows scientists to perform this task in a more realistic and controlled environment and provides powerful tools for the study and better understanding of the propagation of light through a nonstatic medium such as the atmosphere. Free space laser communications (FSLC) and studies in light propagation through the atmosphere are areas which constantly benefit from breakthroughs in technology and in the development of realistic atmospheric turbulence simulators, in particular (Santiago et al. 2011). In this paper, we present the results from the implementation of a phase only spatial light modulator (SLM) as an atmospheric turbulence simulator for light propagation in the short-wave infrared (SWIR) regime. Specifically, we demonstrate its efficacy for its use in an FSLC system, at a wavelength of 1550 nm.

Many electro optical devices are now available for compensating atmospheric distortions in optical systems. To support the characterization of these devices in a consistent fashion a common testbed that physically simulates these atmospheric aberrations is required. This paper reports on a system that realizes seeing conditions ranging from very poor to excellent and feeds these wavefronts to the compensation device under test. The testbed provides quantitative characterization of the system under test and evaluates residual wavefront error.

We present an overview of the Adaptive Polymer Lenses (APLs) program at NRLWe will present the work performed on the use of APLs for applications ranging from imaging, beam control and non-mechanical zoom in the visible, near, short and mid-wave infrared.

We present the combined use of large aperture adaptive lens with large optical power modulation with a multi actuator adaptive lens. The Multi-actuator Adaptive Lens (M-AL) can correct up to the 4th radial order of Zernike polynomials, without any obstructions (electrodes and actuators) placed inside its clear aperture. We demonstrated that the use of both lenses together can lead to better image quality and to the correction of aberrations of adaptive optics optical systems.

This paper reports on the measurement and reconstruction using two algorithms of an Adaptive Tilt Mirror's (ATM) reflected wavefront using a Shack-Hartmann (SH) based wavefront sensor. The ATM consists of a deformable mirror mounted onto a fast steering mirror platform. Reconstruction of the wavefront was performed using Finite Difference and Finite Element reconstruction algorithms for comparison. The SH wavefront sensor with high frame-rate readout camera and the two types of software reconstructors provide a visualization of the ATM's surface while being moved physically on the fast steering mirror platform at a rate of 30 Hz.