A Brewster route to Cherenkov detectors

Cherenkov detectors enable a valuable tool to identify high-energy particles. However, their sensitivity and momentum coverage are limited by the refractive index of host materials. Especially, identifying particles with energy above multiple gigaelectronvolts requires host materials with a near-unity refractive index, which are limited to bulky gas chambers. Overcoming this fundamental material limit is important for future particle detectors yet remains a long-standing challenge. Here, we propose a different paradigm for Cherenkov detectors that utilizes the broadband angular filter made from stacks of variable onedimensional photonic crystals. Owing to the Brewster effect, the angular filter is transparent only to Cherenkov photons from a precise incident angle. Particle identification is achieved by mapping each Cherenkov angle to the peak-intensity position of transmitted photons in the detection plane. Such angular filtering effect, although decreases the photon number collected in the detection plane, enables the realization of a non-dispersive pseudo refractive index over the entire visible spectrum. Moreover, the pseudo refractive index can be flexibly designed to different values close to unity. Our angular-selective Brewster paradigm offers a feasible solution to implement compact and highly sensitive Cherenkov detectors especially in beam lines with a small angular divergence using regular dielectrics.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)National Research Foundation (NRF)Published versionThe work was sponsored by the National Natural Science Foundation of China (NNSFC) under Grants No. 61625502, No. 11961141010, No. 62175212, and No. 61975176, the Top-Notch Young Talents Program of China, Zhejiang University Global Partnership Fund, and the Fundamental Research Funds for the Central Universities (2021FZZX001- 19). Y.L. was sponsored in part by the Singapore Ministry of Education (No. MOE2018- T2-2-189 (S)), A*Star AME IRG grant (No. A20E5c0095), and Programmatic Funds (No. A18A7b0058), National Research Foundation Singapore Competitive Research Program (No. NRF-CRP22-2019-0006 and NRF-CRP23-2019-0007). B.Z. was sponsored in part by Singapore Ministry of Education (No. MOE2018-T2-1-022 (S), MOE2016-T3-1-006, and MOE2019-T2-2-085). I.K. was sponsored in part by the Azrieli Faculty Fellowship, the Israel Science Foundation (Grant No. 831/19), and the European Research Council (Starter Grant no. 851780). This material is based upon work supported in part by the US Army Research Office through the Institute for Soldier Nanotechnologies, under Contract No. W911NF-18-2-0048, and by the Binational USA-Israel Science Foundation (BSF) 2018288