This PDF file contains the front matter associated with SPIE Proceedings Volume 9617, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Multi-conjugate Adaptive Optics (MCAO) is an essential approach to wavefront sensing and control. The concept of MCAO corrects each "layer" of the atmosphere independently. Correction devices (deformable mirrors) are placed in "series" and assigned to correct the isoplanatic patch. MCAO can be approached two ways: with multi-guide stars or multilayer correction. The objective of this paper is to analyze both approaches and assess their effectiveness to achieve their goals. Wavefront correction is being carried out in the Large Binocular Telescope (LBT) by means of multiple Laser Guide Stars. Multi-layer correction is being achieved by the Solar Telescope GREGOR. This paper will analyze both approached for effectiveness in compensating turbulence for distortion correction.

Wavefront sensing is an advanced technology that enables the precise determination of the phase of a light field, a critical information for many applications, such as noncontact metrology, adaptive optics, and vision correction. Here, we reinterpret the operation of wavefront sensors as a simultaneous unsharp measurement of position and momentum. Utilizing quantum tomography techniques we report an experimental characterization and 3D imaging of a multimode laser light.

The present work generalizes the theoretical model of the rotating PSF imaging based three-dimensional (3D) localization of point sources to high numerical aperture (NA) microscopy for which non-paraxial propagation of the imaging beam and the associated nontrivial vector character of light fields must be properly accounted for. Our analysis supports the prospects of simultaneous acquisition of the state of polarization and 3D location of a point source with high-NA objectives. A second approach for doing joint polarimetry and localization using a specialized birefringent plate without the need for high-NA objectives is also discussed briefly.

Digital holography wave-front sensing in the off-axis image plane recording geometry shows distinct potential for directed-energy and remote-sensing applications. For instance, digital holographic detection provides access to the amplitude and wrapped phase associated with an optical field. From the wrapped phase, one can estimate the atmospheric aberrations present and perform adaptive-optics compensation and high-resolution imaging. This paper develops wave-optics simulations which explore the estimation accuracy of digital holography wave-front sensing in the presence of strong atmospheric turbulence and thermal blooming. Specifically, this paper models spherical-wave propagation through varying atmospheric conditions along a horizontal propagation path and formulates the field-estimated Strehl ratio as a function of the image-plane sampling, the coherence diameter, the log-amplitude variance, and the distortion number. Such results will allow one to assess the number of pixels needed in a detector array when using digital holographic detection in the presence of strong atmospheric turbulence and thermal blooming.

It is suggested to reconstruct the phase screens with the use of different deformable mirror types. In this work we present the results of the phase screen reproducing with the use of stacked-actuator deformable mirror and bimorph one. The reconstruction results were compared. The problems of the reconstruction were discussed.

The majority of image quality studies in the field of remote sensing have been performed on systems with conventional aperture functions. These systems have well-understood image quality tradeoffs, characterized by the General Image Quality Equation (GIQE). Advanced, next-generation imaging systems present challenges to both post-processing and image quality prediction. Examples include sparse apertures, synthetic apertures, coded apertures and phase elements. As a result of the non-conventional point spread functions of these systems, post-processing becomes a critical step in the imaging process and artifacts arise that are more complicated than simple edge overshoot. Previous research at the Rochester Institute of Technology's Digital Imaging and Remote Sensing Laboratory has resulted in a modeling methodology for sparse and segmented aperture systems, the validation of which will be the focus of this work. This methodology has predicted some unique post-processing artifacts that arise when a sparse aperture system with wavefront error is used over a large (panchromatic) spectral bandpass. Since these artifacts are unique to sparse aperture systems, they have not yet been observed in any real-world data. In this work, a laboratory setup and initial results for a model validation study will be described. Initial results will focus on the validation of spatial frequency response predictions and verification of post-processing artifacts. The goal of this study is to validate the artifact and spatial frequency response predictions of this model. This will allow model predictions to be used in image quality studies, such as aperture design optimization, and the signal-to-noise vs. post-processing artifact tradeoff resulting from choosing a panchromatic vs. multispectral system.

We describe multi-baseline observations of a geostationary satellite using the Navy Precision Optical Interferometer (NPOI) during the glint season of March 2015. We succeeded in detecting DirecTV-7S with an interferometer baseline length of 8.8 m on two nights, with a brief simultaneous detection at 9.8 m baseline length on the second night. These baseline lengths correspond to a resolution of ~4 m at geostationary altitude. This is the first multiple-baseline interferometric detection of a satellite.

The majority of image quality studies in the field of remote sensing have been performed on systems with conventional aperture functions. These systems have well-understood image quality tradeoffs, characterized by the General Image Quality Equation (GIQE). Advanced, next-generation imaging systems present challenges to both post-processing and image quality prediction. Examples include sparse apertures, synthetic apertures, coded apertures and phase elements. As a result of the non-conventional point spread functions of these systems, post-processing becomes a critical step in the imaging process and artifacts arise that are more complicated than simple edge overshoot. Previous research at the Rochester Institute of Technology's Digital Imaging and Remote Sensing Laboratory has resulted in a modeling methodology for sparse and segmented aperture systems, the validation of which will be the focus of this work. This methodology has predicted some unique post-processing artifacts that arise when a sparse aperture system with wavefront error is used over a large (panchromatic) spectral bandpass. Since these artifacts are unique to sparse aperture systems, they have not yet been observed in any real-world data. In this work, a laboratory setup and initial results for a model validation study will be described. Initial results will focus on the validation of spatial frequency response predictions and verification of post-processing artifacts. The goal of this study is to validate the artifact and spatial frequency response predictions of this model. This will allow model predictions to be used in image quality studies, such as aperture design optimization, and the signal-to-noise vs. post-processing artifact tradeoff resulting from choosing a panchromatic vs. multispectral system.

The purpose of this research effort is to experimentally generate an electromagnetic Gaussian Schell-model beam from two coherent linearly polarized plane waves. As such, the approach uses a sequence of mutually correlated random phase screens on phase-only liquid crystal spatial light modulators at the source plane. The phase screens are generated using a published relationship between the screen parameters and the desired electromagnetic Gaussian Schell-model source parameters. The approach is verified by comparing the experimental results with published theory and numerical simulation results. This work enables the design of an electromagnetic Gaussian Schell-model source with prescribed coherence and polarization properties.

It is well known that turbid medium such as fog or biological tissues causes light scatter. This phenomenon is known as major impediment for imaging and focusing of light. Thus it is important to understand the impact of the turbid medium on the light characteristics, namely intensity and phase distributions. In this work laser beam propagation through the scattering suspension of polystyrene microspheres in distilled water was investigated both theoretically and experimentally. We obtained the dependence of the wavefront aberrations on the particles concentration and shown the existence of high-order symmetric wavefront aberrations of the laser beam passed through turbid medium. The investigation showed that with the use of bimorph deformable mirror the wavefront aberrations of scattered light could be effectively corrected.

An electronic detector of surface plasmon polaritons (SPP) is reported. SPPs optically excited on a metal surface using a prism coupler are detected by using a close-coupled metal-oxide-semiconductor capacitor. Semitransparent metal and graphene gates function similarly. We report the dependence of the photoresponse on substrate carrier type, carrier concentration, and back-contact biasing.

Extreme adaptive optics (XAO) encounters severe difficulties to cope with the high speed (<1kHz), high accuracy and high order requirements for future extremely large telescopes. An innovative high order adaptive optics system using a self-referenced Mach-Zehnder wavefront sensor (MZWFS) allows counteracting these limitations. This sensor estimates very accurately the wavefront phase at small spatial scale by measuring intensity differences between two outputs, with a λ/4 path length difference between its two legs, but is limited in dynamic range due to phase ambiguity. During the past few years, such an XAO system has been studied by our team in the framework of 8-meter class telescopes. In this work, we report on our latest results with the XAO testbed recently installed in our lab, and dedicated to high contrast imaging with 30m-class telescopes (such as the E-ELT or the TMT). After reminding the principle of a MZWFS and describing the optical layout of our experiment, we will show the results of the assessment of the woofer-tweeter phase correctors, i.e., a Boston Micromachine continuous membrane deformable mirror (DM) and a Boulder Nonlinear Systems liquid crystal spatial light modulator (SLM). In particular, we will detail the calibration of the DM using Zygo interferometer metrology. Our method consists in the precise measurement of the membrane deformation while applying a constant deformation to 9 out of 140 actuators at the same time. By varying the poke voltage across the DM operating range, we propose a simple but efficient way of modeling the DM influence function using a Gaussian model. Finally, we show the DM flattening on the MZWFS allowing to compensate for low order aberrations. This work is carried out in synergy with the validation of fast iterative wavefront reconstruction algorithms, and the optimal treatment of phase ambiguities in order to mitigate the dynamical range limitation of such an MZWFS.

A structure similar to the direct detection of the DPSK signals using polarization dependent free space Mach-Zehnder interferometer is set up to validate its ability for coherent ranging. M sequence is adopted for its superior performance in code compression. The resultant signal voltage is sampled instead of being zero crossing detected and cross-correlated with the modulation signal sampled at the same rate. The ranging peak appears in the one target setup after proper calibration of the interferometric bias point but doesn’t imply any correct range information. For the two range resolved targets, the output image doesn’t depict two independent peaks. The further study is being conducted.

On the basis of the Poisson photocurrent statistics in the photon-limited heterodyne detection, in this paper, the signal-to-noise ratios in the receiver in the time domain and on the focused 1-D image and 2-D image in the space domain are derived for both the down-looking and side-looking synthetic aperture imaging ladars using PIN or APD photodiodes. The major shot noises in the down-looking SAIL and the side-looking SAIL are, respectively, from the dark current of photodiode and the local beam current. It is found that the ratio of 1-D image SNR to receiver SNR is proportional to the number of resolution elements in the cross direction of travel and the ratio of 2-D image SNR to 1-D image SNR is proportional to the number of resolution elements in the travel direction. And the sensitivity, the effect of Fourier transform of sampled signal, and the influence of time response of detection circuit are discussed, too. The study will help to correctly design a SAIL system.

The static-mode down-looking synthetic aperture imaging ladar (SAIL) can keep the target and carrying-platform still during the collection process. Improvement of the signal-to-noise ratio in static-mode down-looking SAIL is investigated. The signal-to-noise ratio is improved by increasing scanning time and sampling rate in static-mode down-looking SAIL. In the experiment, the targets are reconstructed in different scanning time and different sampling rate. As the increasing of the scanning time and sampling rate, the reconstructed images become clearer. These techniques have a great potential for applications in extensive synthetic aperture imaging ladar fields.

In Synthetic aperture imaging ladar (SAIL), the polarization state change of the backscattered light will affect the imaging. Polarization state of the reflected field is always determined by the interaction of the light and the materials on the target plane. The Stokes parameters, which can provide the information on both light intensity and polarization state, are the ideal quantities for characterizing the above features. In this paper, a measurement system of the polarization characteristic for the SAIL target materials is designed. The measurement results are expected to be useful in target identification and recognition.

Large field of view of the coherent receiver requires large detector photosurface area, but with the increase of detector photosurface area, the SNR (signal-to-noise ratio) of the coherent receiver will decline. A balanced photodetection with large photosurface APD can not only increase the angular field of view, and can guarantee the detection sensitivity, which satisfy the coherent receiver’s requirements. An experimental measurement of a balanced APD photodetection is reported.

The implementation of down-looking Synthetic Aperture Imaging Ladar(SAIL) uses quadratic phase history reconstruction in the travel direction and linear phase modulation reconstruction in the orthogonal direction. And the linear phase modulation in the orthogonal direction is generated by the shift of two cylindrical lenses in the two polarization-orthogonal beams. Therefore, the fast-moving of two cylindrical lenses is necessary for airborne down-looking SAIL to match the aircraft flight speed and to realize the compression of the orthogonal direction, but the quick start and the quick stop of the cylindrical lenses must greatly damage the motor and make the motion trail non-uniform. To reduce the damage and get relatively well trajectory, we make the motor move like a sinusoidal curve to make it more realistic movement, and through a resampling interpolation imaging algorithm, we can transform the nonlinear phase to linear phase, and get good reconstruction results of point target and area target in laboratory. The influences on imaging quality in different sampling positions when the motor make a sinusoidal motion and the necessity of the algorithm are analyzed. At last, we perform a comparison of the results of two cases in resolution.

The design and laboratory experiment of a demonstrator of all-optronic down-looking synthetic aperture imaging ladar (SAL) is presented in this paper, in which the sensing-to-processing chain is carried out with light. The ultra-fast processing capability from image acquisition to real-time reconstruction is shown. The demonstrator consists of a down-looking SAL unit with a beam scanner and an optical processor. The down-looking SAL unit has a transmitter of two coaxial orthogonally polarized beams and a receiver of polarization-interference self-heterodyne balanced detection. The linear phase modulation and the quadratic phase history are produced by the projection of movable cylindrical lenses. Three functions of strip-map mode, spotlight mode and static mode are available. The optical processor is an astigmatic optical system, which reduces to a Fourier transform system and a free-space of the Fresnel diffraction to realize the matched filtering. A spatial light modulator is used as the input interface. The experiment is performed with an optical collimator. The system design is given, too. The down-looking SAL has the features such as a big coverage with an enhanced receiving aperture and little influence from atmospheric turbulence and the optical processor is simple.

As we all know, because the index of refraction of the conventional microlens array (MLA) is not variable, the wavefront sensor based on the conventional MLA can only obtain the intensity image with low-resolution when it is used to measure the wavefront information simultaneously. In this paper, we use the dual-mode photosensitive arrays based on the liquid crystal (LC) MLA and CMOS sensors to obtain both intensity images with high-resolution and wavefronts. The dual-mode photosensitive arrays can work between an imaging mode and a wavefront sensor mode by switching the voltage off and on. In the experiment, we compare the composite wavefront of the object exposured in a white light with the wavefronts of the same object in tricolor laser. Because using the monochromatic light to measure the wavefront of an object may loss some information, it is a better method to use the white light for obtaining the wavefront information of the single object in the black background. We also discussed how to mix the wavefronts of the red green and blue laser to make the mixed wavefront which is closer to the composite wavefront.