It is no exaggeration to say that the development of imaging sensors has made profound impact on our life, from a smartphone camera to the most advanced medical imaging equipment, and even to space exploration. Besides its intensity and color, light is also characterized by its polarization state that can be affected by emission, scattering or transmission of an object. Detecting light polarization has been proven to be essential for various applications such as biomedical diagnostics, remote sensing, target detection and astronomy. Yet, despite the fact that the sensitivity, speed, pixel density and color range of image sensors have been continuously improved, the capability of full-polarization imaging, hasn't been realized on monolithically integrated sensors. This project is to develop a chip-integrated imaging sensor array, or in another word, polarimetric imaging array, to detect not only light intensity and color but also the complete polarization state of light. Such a compact system can be further incorporated into many portable systems for clinic diagnostics, real time environmental monitoring network, or a smartphone polarimeter for field study and research. By integrating research and education, the project is aimed to inspire and cultivate the next-generation of scientists and engineers in nanophotonics and nanotechnology to address grand challenges in health, security, environmental issues and space exploration. In particular, the proposal aims to promote participation in science and engineering (esp. under-represented groups) by engaging undergraduate students in research, showcasing research to K-12 students through outreach and a summer enrichment program. The scientific objective of this project is to investigate the feasibility of integrating artificially engineered planar optics to realize on-chip polarimetric imaging sensor array. Conventional polarimetric sensing and imaging systems are very bulky and require moving parts, which makes it difficult for minimization. Moreover, these systems also suffer from reduced frame rate and inaccuracy of extracted polarization information due to motion in the scene. Monolithic integrated polarimetric imaging systems have been extensively studied; however, these polarimetric imaging systems have various limitations, such as large pixel size, degradation in imaging quality, lack of compatibility with silicon technology and poor accuracy. The proposed technology fully exploits the cutting-edge development in nanophotonics and nanofabrication to provide significantly improved solutions for on-chip polarimetric sensing and imaging applications. All the detection elements are realized based on subwavelength-thick structures directly integrated onto silicon photodetectors. The polarization extinction ratios and transmission efficiency are 30 and >40% in the visible range for all polarization detection elements, respectively. The fabrication process developed in this project is compatible with CMOS technology, and well tolerates a lateral alignment error as large as tens of nanometers. All these detection elements can be made down to submicrometer size while still maintaining reasonably good performance, feasible for large-scale inexpensive CMOS production. The project will lead to the realization of on-chip polarimetric imaging sensor arrays with high sensitivity and accuracy. Moreover, the research will enable an in-depth understanding of the fundamental device physics and fabrication techniques involved in integrating metasurface flat optics on chip, which is essential for realizing ultra-compact optical system with other unique properties and unprecedented functionalities.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
