Dmitry Vorobiev

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Current and Past Research

Polarization-Sensitive Sensors
My current research focus is the development of imaging sensors that are sensitive to the polarization of light, at the sensor level. Polarization is a fundamental property of light, along with frequency and coherence, which describes the direction of oscillation of the electric field. Polarization is a powerful probe of large scale geometry of objects and of microscopic structure. Measurements of polarization can be used to infer the shape and structure of objects even if they are too small or too far away for their shape to be resolved optically.

Unfortunately, neither human eyes, nor the imaging sensors we have developed are sensitive to polarization. This creates the need for complex schemes that modulate the intensity of light based on its polarization, which can be used to derive the polarization state. Usually these schemes employ many polarization optics and moving parts. Performing the modulation at the pixel level allows the fabrication of polarimeters that are compact, lightweight, mechanically robust and capable of capturing the needed intensity information with a single exposure.

I design, simulate, fabricate and characterize these devices for the optical and infrared regimes. My intent is to investigate their fundamental performance limits, develop optimal fabrication strategies and determine their utility and proper calibration in astronomy, remote sensing and biomedical imaging.
Measurement Astrophysics
At the University of New Mexico, I worked with John McGraw's Measurement Astrophysics group on a NIST-funded project to generate a catalog of precise spectrophotometric standard stars. Calibrated standard stars are objects whose brightness is known absolutely (Watts/m2/nm). This allows their use as calibration (and cross-calibration) targets for astronomical telescopes and remote sensing satellites.

Absolute measurements of the brightness of astronomical objects are rarely made, because such measurements must account for the time-variable transmission of the Earth's atmosphere. The MAP team developed a technique to measure the transmission of Earth's atmosphere directly, using the Atmospheric LIDAR for Extinction (ALE) (pictured here). ALE can be used to point near an object of interest and measure the transmission of the atmosphere along the light of sight of the telescope making the observations. This obviates the need for many assumptions about the structure of Earth's atmosphere, greatly reducing the measurement uncertainty.

I used ALE to make precise photometric observations of variable stars to evaluate this novel technique. Our results were encouraging, and the MAP team is currently using the the Facility Lidar for Atmospheric Measurements of Extinction (FLAME), the successor to ALE, and the Atmospheric Extinction Spectrophotometer (AESOP) to develop the most precise and accurate catalog of spectrophotometric standards to date.