“…In the past half century, potassium tantalate-niobate (KTN) crystals have attracted a lot of attention in the research and application field because of their exceptional electro-optic (EO) properties and wide transparent wavelength range [1][2][3][4][5][6][7][8] . Thus, they have been used in EO modulation [2,5] , beam deflection [6][7][8] , electric-controlled lenses [9] , and so on. Recent research shows that in the proximity of the Curie temperature, a KTN crystal presents enhanced EO properties and a few kinds of fascinating critical phenomena, i.e., giant EO effects [7,10] , scale-free optics and anti-diffraction beam propagation [11,12] , solitons [13,14] , extreme nonlinearity [15] , and 3D super crystals [13,[16][17][18][19] .…”