Deep Trenches in ${\rm LiNbO}_{3}$: Experimental Demonstration of Modulator Extinction Ratio Enhancement

We benefit from the recent progress on lithium niobate deep etching to enhance the extinction ratios of Mach-Zehnder modulators. We demonstrate that a proper trench placed in between parallel arms can lead to a 15 dB-increase without any additional losses at 1550 nm.