High-Bandwidth Lumped Mach-Zehnder Modulators Based on Thin-Film Lithium Niobate

Recently, lumped Mach-Zehnder Modulators (MZMs) have received renewed attention due to their potential for low power consumption and compact size. However, the practicality of lumped MZMs with conventional lumped electrodes (C-LEs) is limited by their lower electro-optical (EO) bandwidth. The reduction in EO bandwidth results from the inherent trade-off between EO bandwidth and half-wave voltage length product (V pi L) within the C-LE architecture. This paper proposes a thin-film lithium niobate (TFLN)-based lumped MZM with capacitively-loaded lumped electrodes (CL-LEs). The purely linear EO effect of the LN eliminates the parasitic capacitance in the doped PN junction and enhances the EO bandwidth. Furthermore, the CL-LE structure can break the limitation between EO bandwidth and V pi L inherent in the C-LE design. Simulations show the proposed device achieves a high EO bandwidth of 32.4 GHz and a low V pi L of 1.15 V<middle dot>cm. Due to the reduced capacitance and lower V pi L, the power consumption of the device is as low as 0.1 pJ/bit. Simulation results indicate that the open-eye diagrams are achieved at 64 Gb/s for 1.5 mm TFLN lumped MZM, with an ER of 2.97 dB. Consequently, the proposed device architecture substantially enhances the performance of lumped MZMs, showing promise for application in short-reach optical interconnects within data centers.