Plasmonic Metasurface-Enabled Differential Photodetectors for Broadband Optical Polarization Characterization

The polarization state of an optical field is central to applications in optical communications, imaging, and data storage as well as furthering our understanding of biological and physical systems. Here we demonstrate two silicon photodetectors integrated with aluminum nanoantennas capable of distinguishing orthogonal states of either linearly or circularly polarized light with no additional filters. The localized plasmon resonances of the antennas lead to selective screening of the underlying silicon from light with a particular polarization state. The planar device, fully compatible with conventional CMOS fabrication methods, incorporates antennas sensitive to orthogonal states of polarization into two back-to-back Schottky photodetectors to produce a differential electrical signal that changes sign as the polarization of an incident optical beam changes from one basis state to the orthogonal state. The non-null response of the devices to each of the basis states expands the potential utility of the photodetectors while improving precision. Each device is wrapped into a spiral footprint to provide compatibility with the circular profile of conventional optical beams and has an overall diameter of 50 μm. The sensitivity of these devices is demonstrated experimentally over a wavelength range from 500 to 800 nm, establishing their potential for integration into a wide range of optical systems.