Characterization of the temporal phase fluctuations in a weak atmospheric turbulence regime as a random bit-stream generator.

This paper investigates the extent to which atmospheric turbulence can be exploited as a random bit generator. Atmospheric turbulence is considered an inherently random process due to the complex inhomogeneous system composition and its sensitivity to changes in pressure, temperature, humidity, and wind conditions. A self-calibrating Mach-Zehnder interferometer was used to collect phase fluctuations in the temporal domain introduced to an optical beam propagating through the atmosphere.

Large aperture adaptive doublet polymer lens for imaging applications.

We report a full design process-finite element modeling, fabrication, and characterization-of adaptive doublet polymer lenses. A first-order model was developed and used to design fluidic doublets, analogous to their glass counterparts. Two constant-volume fluidic chambers were enclosed by three flexible membranes, resulting in a variable focal length doublet with a clear aperture of 19.

Navy Prototype Optical Interferometer observations of geosynchronous satellites.

Using a 15.9  m baseline at the Navy Prototype Optical Interferometer (NPOI), we have successfully detected interferometric fringes in observations of the geosynchronous satellite (geosat) DirecTV-9S while it glinted on two nights in March 2009. The fringe visibilities can be fitted by a model consisting of two components, one resolved (≳3.

Light propagation through anisotropic turbulence.

A wealth of experimental data has shown that atmospheric turbulence can be anisotropic; in this case, a Kolmogorov spectrum does not describe well the atmospheric turbulence statistics. In this paper, we show a quantitative analysis of anisotropic turbulence by using a non-Kolmogorov power spectrum with an anisotropic coefficient. The spectrum we use does not include the inner and outer scales, it is valid only inside the inertial subrange, and it has a power-law slope that can be different from a Kolmogorov one.

Analysis of a combined tip-tilt and deformable mirror.

A deformable mirror mounted on a two-axis tilt platform can provide wavefront compensation at a single location in an adaptive optics system, resulting in a significant reduction in the number of optical components in the system and in a simplification of the alignment. However, the moment of inertia of a deformable mirror is significantly different from that of the monolithic mirror commonly mounted on a tilt platform. We report on what are to our knowledge the first experimental results of mounting a microelectromechanical deformable mirror onto a fast steering platform and the first observation that at low operating frequencies high-order deformation of the deformable mirror membrane was not recorded.

Generalized phase diversity for wave-front sensing.

Phase diversity is a phase-retrieval algorithm that uses a pair of intensity images taken symmetrically about the wave front to be determined. If these images are taken about the system input pupil this is equivalent to a curvature-sensing algorithm. Traditionally a defocus aberration kernel is used to produce the phase-diverse data.

Demonstration of new technology MEMS and liquid crystal adaptive optics on bright astronomical objects and satellites.

We present here results using two novel adaptive optic elements, an electro-static membrane mirror, and a dual frequency nematic liquid crystal. These devices have the advantage of low cost, low power consumption, and compact size. Possible applications of the devices are astronomical adaptive optics, laser beam control, laser cavity mode control, and real time holography.

Fast steering, high-resolution imaging system.

High-resolution imaging can be dramatically improved by combining a fast image stabilization system and variable aperture masking. We describe an imaging system that provides high-resolution images through an annular aperture using the unwanted low spatial frequency light for image stabilization. The annulus thickness and diameter can be selected to enhance the contribution of different spatial frequencies in the image at the expense of image exposure time.

Foveated imaging demonstration.

A wide field-of-view (FOV), theoretically diffraction-limited imaging system is demonstrated using a single positive lens (a singlet), a reflective liquid crystal spatial light modulator (SLM), a turning mirror and a CCD camera. The SLM is used to correct the off-axis aberrations that would otherwise limit the useful FOV of our system. Foveated imaging refers to the variation in spatial resolution across the image caused by using the SLM in this manner.