Recently, researchers from the Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS) have proposed a novel measurement method of the electro-optic (EO) coefficient based on the χ(2) nonlinear optical technology to measure the linear EO coefficients of KH2PO4 (KDP) and K(H1'xDx)2PO4 (DKDP) precisely. Relevant results were published in Optics Express on Jan. 18, 2021.