Fig. 1: Experimental realization of topologically controlled THz localization.
From: Topologically tuned terahertz confinement in a nonlinear photonic chip
a Illustration of nonlinear generation and confinement of THz-waves in an SSH-type microstructure. The LN structure undergoes a transition from L-LD, through equidistant, to S-SD regions along the +z-axis, illustrated by colors shaded from orange into blue. The polarization of the THz electric field and that of the optical pump beam are all along the direction of the LN crystalline axis (z-axis). b Microscope image of the LN array structure fabricated by fs-laser writing. The thickness of the LN chip is 50 μm in the y-direction. The total length of the microstructure along the z-direction is \(L = 6\,{{{\mathrm{mm}}}}\). d1 and d2 are the spacings between neighboring LN stripes corresponding to the coupling coefficients c1 and c2, respectively. At the dashed yellow line, z = L/2 and d1 = d2 = 55 μm, which leads to an equidistant structure. The SSH lattice contains an L-LD (\(d_1 \,>\, d_2\)) region above the line and an S-SD (\(d_1 \,<\, d_2\)) region below the line. A–E denote the locations corresponding to \(z = 0\), L/8, L/2, 7L/8, L. Here n numbers the LN waveguides (lattice sites). Red and blue dashed lines mark the topologically nontrivial and trivial parts of the SSH lattice
