Andrey Alenin

Bio: Andrey Alenin is an academic researcher from University of New South Wales. The author has contributed to research in topics: Mueller calculus & Bandwidth (signal processing). The author has an hindex of 11, co-authored 50 publications receiving 323 citations. Previous affiliations of Andrey Alenin include University of Arizona.

Generalized channeled polarimetry.

Abstract: Channeled polarimeters measure polarization by modulating the measured intensity in order to create polarization-dependent channels that can be demodulated to reveal the desired polarization information. A number of channeled systems have been described in the past, but their proposed designs often unintentionally sacrifice optimality for ease of algebraic reconstruction. To obtain more optimal systems, a generalized treatment of channeled polarimeters is required. This paper describes methods that enable handling of multi-domain modulations and reconstruction of polarization information using linear algebra. We make practical choices regarding use of either Fourier or direct channels to make these methods more immediately useful. Employing the introduced concepts to optimize existing systems often results in superficial system changes, like changing the order, orientation, thickness, or spacing of polarization elements. For the two examples we consider, we were able to reduce noise in the reconstruction to 34.1% and 57.9% of the original design values.

Adapting the HSV polarization-color mapping for regions with low irradiance and high polarization

Abstract: Many mappings from polarization into color have been developed so that polarization information can be displayed. One of the most common of these maps the angle of linear polarization into color hue and degree of linear polarization into color saturation, while preserving the irradiance information from the polarization data. While this strategy enjoys wide popularity, there is a large class of polarization images for which it is not ideal. It is common to have images where the strongest polarization signatures (in terms of degree of polarization) occur in regions of relatively low irradiance: either in shadow in reflective bands or in cold regions in emissive bands. Since the irradiance is low, the chromatic properties of the resulting images are generally not apparent. Here we present an alternate mapping that uses the statistics of the angle of polarization as a measure of confidence in the polarization signature, then amplifies the irradiance in regions of high confidence, and leaves it unchanged in regions of low confidence. Results are shown from an LWIR and a visible spectrum imager.

Optimal bandwidth micropolarizer arrays

Abstract: Currently, the best performing micropolarizer array is the 2×4 pattern introduced by LeMaster and Hirakawa. In this Letter, we extend the available set of patterns with the aim of improving reconstruction quality by leveraging the Fourier domain and designing information carriers that yield optimal bandwidth. First, the family of 2×L patterns widens the optimization space of the 2×4 pattern by facilitating variable allocation of bandwidth for channels surrounding polarization and intensity carriers. Second, the 2×2×N patterns present an intriguing option for use within a hybrid spatiotemporal modulation scheme, in which the multiple temporal measurements enable maximum theoretical spatial resolution of reconstructed Stokes parameters.

Optimal bandwidth and systematic error of full-Stokes micropolarizer arrays.

Abstract: In this paper, we present the first in-depth analysis of the bandwidth tradeoffs, error performance, and noise resiliency of full-Stokes micropolarizer array (MPA) designs. By applying our Fourier domain tools that provide a systematic way for arranging information carriers and allocating bandwidth, we develop a number of new full-Stokes MPA layouts and compare them to the existing full-Stokes MPAs in the literature, all of which use 2×2 pixel unit cells to build the MPA. We compare the reconstruction accuracy afforded by these traditional designs with the generalized 2×L family of MPAs, a 3×3 tiling, as well as a 2×2×3 layout that uses multiple snapshots and trades off temporal resolution for spatial resolution. Of those systems, the hybrid spatiotemporally modulated 2×2×3 MPA provisions the most bandwidth and provides the highest reconstruction accuracy, while the modified 2×L family remains the best performing single-snapshot MPA. Additionally, we study the degradation of reconstruction accuracy under the presence of systematic error in MPA fabrication. We find that reducing the amount of correlated error is by far the largest factor in ensuring robust performance.

Design considerations for an optical link supporting intersatellite quantum key distribution

Abstract: Quantum key distribution (QKD) is a method for establishing secure cryptographic keys between two parties who share an optical, “quantum” channel and an authenticated classical channel. To share such keys across the globe, space-based links are required and in the near term these will take the form of trusted node, key management satellites. We consider such channels between two nanosatellite spacecraft for polarization entanglement-based QKD, and the optical channel is described in detail. Quantum channels between satellites are useful for balancing keys within constellations of trusted node QKD satellites and, in the future, may have applications in long-distance qubit exchange between quantum computers and in fundamental physics experiments. The nanosatellite mission proposed uses an optical link with 80-mm diameter optical terminals. If such a link could be maintained with 10-μrad pointing accuracy, then this would allow QKD to be performed for satellite separations up to around 400 km. A potential pointing and tracking system is also described although currently this design would likely limit the satellite separation to 100 to 150 km.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Linear Systems, Fourier Transforms and Optics

Abstract: (1979). Linear Systems, Fourier Transforms and Optics. Optica Acta: International Journal of Optics: Vol. 26, No. 7, pp. 836-836.

An overview of polarimetric sensing techniques and technology with applications to different research fields

Abstract: We report the main conclusions from an interactive, multidisciplinary workshop on “Polarimetric Techniques and Technology”, held on March 24-28 2014 at the Lorentz Center in Leiden, the Netherlands. The work- shop brought together polarimetrists from different research fields. Participants had backgrounds ranging from academia to industrial RD. Here we provide an overview of polarimetric instrumentation in the optical regime geared towards a wide range of applications: atmospheric remote sensing, target detection, astronomy, biomedical applications, etc. We identify common approaches and challenges. We list novel polarimetric techniques and polarization technologies that enable promising new solutions. We conclude with recommendations to the polarimetric community at large on joint efforts for exchanging expertise.

Polarization state generation and measurement with a single metasurface.

Abstract: The constituent elements of metasurfaces may be designed with explicit polarization dependence, making metasurfaces a fascinating platform for new polarization optics. In this work we show that a metasurface grating can be designed to produce arbitrarily specified polarization states on a set of defined diffraction orders given that the polarization of the incident beam is known. We also demonstrate that, when used in a reverse configuration, the same grating may be used as a parallel snapshot polarimeter, requiring a minimum of bulk polarization optics. We demonstrate its use in measuring partially polarized light, and show that it performs favorably in comparison to a commercial polarimeter. This work is of consequence in any application requiring lightweight, compact, and low-cost polarization optics, polarimetry, or polarization imaging.