Novel Miniaturized Photodetector for Characterizing Arbitrary Polarization

An international team led by Prof. Wei Li from the Changchun Institute of Optics, Fine Mechanics, and Physics (CIOMP) of the Chinese Academy of Sciences conducted a new study published in Nature. The study introduces a novel miniaturized photodetector that characterizes arbitrary polarization states across a broadband spectrum with a single device and measurement.

Traditional photodetectors are limited to measuring light intensity alone. Existing polarization and spectrum photodetectors often rely on the complex integration of multiple polarization- or wavelength-sensitive elements in time or space to enhance detection capabilities. Current photodetectors typically sacrifice one dimension of information for another; they can measure either intensity and polarization at a fixed wavelength or intensity and wavelength under uniform polarization.

Wei Li, Professor, Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), Chinese Academy of Sciences

Cheng-Wei Qiu, a Professor from the National University of Singapore, said, “This limitation means that existing methods can only detect light fields with predetermined polarization or wavelength values projected onto a three-dimensional parameter space, thereby losing degrees of freedom needed for many natural scenarios where light may carry arbitrary changes in polarization and intensity across a broad spectrum.”

The group modulated converging light fields with wavevector-dependent responses across various azimuthal and incidence angle channels by utilizing spatial dispersion on a frequency-dispersion interface. They first found that, according to Fresnel’s formula, even the most basic dispersive surfaces, when subjected to oblique incidence, show certain polarization and wavelength responses, which can be further intensified by resonance.

Based on this, the interfaces, supported by deep residual networks for decoding high-dimensional polarization and spectrum information, could map light from all channels, conveying rich polarization and spectrum information in a single image via a uniform dispersion layer.

Our photodetector is capable of demonstrating high spectral resolution and accurate reconstruction of full-Stokes polarization states in both theoretical and experimental settings. Precision detection of high-dimensional information by our photodetector, such as a two-color laser field with different polarization states or broadband reflection from a gold interface exhibiting varying polarization states, is achieved beyond the capabilities of commercial polarimeter and spectrometer.

Chunqi Jin, Assistant Professor, Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), Chinese Academy of Sciences

Jin added, “Additionally, this approach can be extended to imaging applications by sandwiching the film with a commercial microlens array and sensor array to realize ultra-compact high-dimensional imager.”

Prof. Wei Li suggests that ultra-broadband detection will be possible in the future through the integration of broadband commercial photodetectors, that photonic crystals, metasurfaces, and two-dimensional materials as alternatives to currently used thin film schemes will further improve detection resolution, and that the integration of image processing and distance measurement will enable higher-dimensional detection capabilities.

He also envisions that integrating physical and deep learning models will improve deciphering performance and minimize the need for a priori resources.

This method will revolutionize the field of high-dimensional photodetection and imaging technologies, representing a noteworthy advancement in the characterization of light.

Fan, Y., et al. (2024) Dispersion-assisted high-dimensional photodetector. Nature. doi:10.1038/s41586-024-07398-w.