Figure 1

Experimental-setup, the crystallographic orientation and morphology of the multilayered single crystal LN thin film system employed for THz wave modulation.

(a) Schematic of the multilayered thin film system comprising an ion-sliced single crystal z-cut LN (504 nm thick) deposited on platinized silica grown on an LN substrate (500 μm thick). The top layer is excited by applying an external a.c. field via two silver electrodes deposited at opposite corners diagonally placed on the surface. (b) Illustration of the reshaping of a THz wave due to its interaction with a piezoelectric crystal whose index of refraction is subject to a localized polarization gradient. The wave gets compressed at the positive slope of the index and expanded at the negative slope of the index. (c) AFM micrograph (2 μm × 2 μm) of the surface of the thin film system. It depicts a smooth surface topography with the roughness having a root mean square value of (Rq) ~ 0.194 nm as shown in the inset. (d) XRD spectrum confirms the crystal orientation of the LN thin film system, deposited on Pt (111), being Z-axis (00 l) in pure rhombohedral phase (with the simulated crystal structure in the inset). Pure phase of both the substrate and the top layer of LN are prominently visible in the peak doublets (see the inset). (e) THz transmission spectra of the platinized thin film system. As calculated from the skin depth σ_s of platinum,the embedded 400 nm thick layer is opaque to THz waves resulting in a very low transmission amplitude therefore making the system suitable for reflection mode of operation where the loss of incident energy due to transmission is low.