Creating optical polarimetry on a silicon chip

Ohio State University, The, Columbus OH

Investigators

Abstract

Abstract title: Creating optical polarimetry in miniature photonic integrated circuits for point-of-need materials identification, chemical and biological analysis, and environmental sensing Abstract: Non-technical description: Optical polarimetry provides a unique lens for achieving contrast in sensing systems, conveying information that generally cannot be acquired by any other means. The uniqueness of polarization signatures yields applications that span virtually all areas of science and technology, including materials characterization, chemical and biological analysis, remote sensing of the environment, and measurements of astronomical objects. The state-of-the-art in optical polarimetry involves, however, relatively large and bulky instrumentation that lacks portability and requires extensive alignment, restricting measurements to the laboratory. Miniaturization of optical polarimeters to the scale of a microelectronic circuit would transform polarimeters from large-scale laboratory instrumentation to portable point-of-need platforms. Unique sensing modalities become possible for applications spanning real time monitoring of hyperglycemic swings, analysis of trace chemical compounds, and development of biotechnology relevant to food industries. The societal importance of miniaturized sensor systems drives the focus of the integrated educational plan. The plan responds to the challenge of linking science and engineering to increasingly global societal problems by developing a global scientist and engineer conduit, creating new modules for integrated optics curriculum that engenders integrative research thinking, and involving graduate and undergraduate students, underrepresented groups, and minorities in the research program. Technical description: To date, virtually all sensing modalities based on spectral and intensity information of a sample have been miniaturized from laboratory scale instrumentation to the scale of a microelectronic circuit, except for optical polarimetry. Optical polarimetry has not been accessible on the chip-scale because the sensing modality requires polarization controlling components such as retarders and polarizers that are implemented in bulk crystals or optical fiber. Manipulating the state of polarization on a photonic integrated circuit has proven to be elusive. To overcome this obstacle, a comprehensive research program is proposed involving theory, design, analysis, fabrication, and test to realize optical polarimetry on a silicon chip for the first time. The objectives are to experimentally demonstrate an on-chip arbitrary polarization state generator and an on-chip arbitrary polarization state analyzer that are interconnected by a region that overlaps the optical wave with a sample of interest. The approach harnesses the polarization rotating properties of Berry's phase in three-dimensional silicon optical waveguides. Photonic integrated circuits will be created that are capable of generating and determining arbitrary states of polarization. Polarimetric measurements of dichroism, diattenuation, optical activity, birefringence, and depolarization are brought to the chip-scale. The design and modeling approach is based on polarization dependent coupled mode theory and numerical solutions of Maxwell's equations. The chip will be fabricated at Ohio State University using nano-scale fabrication techniques. A host of samples in the solid and liquid phases will be measured for the purposes of test, measurement, and validation. Measurements will be compared with current laboratory scale optical polarimeters. Transformational point-of-need polarimetric sensor system architectures in integrated circuits are envisioned.