The mechanism of the color routing effect with the selective electron beam excitation at the nanoscale has been uncovered by Cheng Chi et al. from Beijing Engineering Research Center of Mixed Reality and Advanced Display, School of Optics and Photonics, Beijing Institute of Technology, and colleagues in a recent study published in Light: Science & Applications.
Design of on-chip CRs and its photon momentum modulation function. a Schematic of electron-induced CRs. Symmetrical Au nanoantenna under electron beam stimulation at the nanoantenna corner generates asymmetrical dichromatic dispersion radiation. b Experimental and simulated spectra obtained from Au nanoantenna. The blue (black) curve corresponds to the experimental (simulated) spectrum. The peak positions of green and red components are marked with arrows. c Schematic of dichromatic component analysis. Four quarters from I to IV are introduced to detect dichromatic photon propagation directions. d Pseudo-color scanning electron microscopy image of a single Au nanoantenna. The stimulation position is located at the upper-right corner of the Au nanoantenna. e scattering ratio of different angular quarter sphere detection, where the ratio value of the red (green) component is defined to be positive (negative) as a distinction. The error bar represents the uncertainty of the scattering ratio in multiple experiments. f Simulated angular patterns of green components and red components for signals. The nanoantenna size and stimulation position are the same as d. g Measured angular patterns of green (left) and red (center) components. The differential angular pattern is shown on the right. The axis in g is the same as in f. h Intensity ratio of the red and green components in each region. The error bar represents the uncertainty of the intensity ratio, which is extracted from multiple measurements. Image Credit: Cheng Chi et al.
The color routing effect offers a novel method for controlling photon momentum in both frequency and spatial domains while maximizing spectrum usage. Color routers were used in the study of propagating light wavefront modification to split light with different frequencies into distinct directions. This approach has been used in light manipulation using multi-frequency channels, including photonic crystal waveguides and frequency-encoded quantum information processing.
Color routers that control the momentum of photons in multi-frequency channels can be used for display and information technologies, particularly optical information encoding and encryption with low crosstalk and high dimensionality, since photons are effective information carriers with high capacity and robustness.
Previous research on color routers has mostly been on structure design, where metasurfaces, nanoantennas, and gratings can be used to modulate photon momentum. However, this technique is still challenging for future on-chip applications because of the lack of flexible manipulation at the nanoscale. An effective solution must be suggested for active controllable color routers to reach their full potential in optical information applications.
Based on this mechanism, they created a programmable electron-induced color router array, which allows a field-programmable gate array to individually control each nanoantenna’s emission modes with electron beam shift at the nanoscale.
The researchers created an encrypted display device using programmable modulation of the color router array. This device uses dichromatic photon momentum and beam intensity as carriers to improve information processing ability, resulting in increased information capacity based on frequency-dependent angular measurement.
The geographic distribution of active unit cells represents the desired image for display. However, the constant integrated intensity ratio between the green and red components across the entire angular space with varying impinging positions prohibits traditional intensity detection from reading out the encoded information.
The distinct angular patterns of dichromatic photon momentum splitting in momentum space hold the key to deciphering the encrypted image. The use of erasure code strengthens the encoding process, contributing to a dependable encryption solution.
This frequency-dependent encrypted display overcomes the light diffraction limit by adjustable electron excitation and enables the deep subwavelength scale leveraging of dichromatic photon momentum, which serves as coding information.
“In this work, we demonstrate a modulation method of dichromatic photon momentum via electron-induced color routers at a deep subwavelength scale. The conversion of the featured radiation pattern can be triggered by steering the electron beam's impact position. The active modulation of dichromatic photon splitting can be effectively achieved by altering the far-field interference of dipole and quadrupole moments with judiciously adjusted impinging position,” the researchers added.
They further added, “More importantly, based on this principle of electron-induced color routers, we realize a programmable encrypted display device with the color router array, which provides a compelling platform for the manipulation of photon momentum at the nanoscale and paves the way for future quantum information technology and integrated photonic systems.”
“Features of deep subwavelength scale modulation, large information capacity, and enhanced security make this encrypted display device a promising candidate for information storage and processing, where high integration and minuscule size broaden its practical applications,” they further stated.
“Our work provides a demonstration of modulating photon momentum via electron-induced color routing effect and programmable color router array for encrypted display, which can ignite modern interdisciplinary research in the advanced display, on-chip spectroscopy, optical communication, and related applications in integrated quantum information technology,” the researchers forecasted.
Journal Reference:
Chi, C., et al. (2025) Programmable electron-induced color router array. Light Science & Applications. doi.org/10.1038/s41377-024-01712-x.