Compact thin-film lithium niobate dual-stage intensity modulator with ultrahigh linearity

Abstract

The linearity of modulators fundamentally determines the critical performance of microwave-to-optical signal conversion in photonic systems. This work presents a compact dual-stage cascaded intensity modulator based on thin-film lithium niobate (TFLN), which overcomes the linearity constraints of conventional Mach–Zehnder modulators (MZMs) through an innovative two-stage architecture. The proposed device integrates a cascaded dual-MZM configuration with a nonlinear component cancellation strategy, achieving concurrent suppression of both third-order and fifth-order components in third-order intermodulation distortion (IMD3). The experimentally measured spurious-free dynamic range (SFDR) reaches 122.3 dB·Hz 6/7 at 1 GHz and remains 111.26 dB·Hz 4/5 in the 20 GHz high-frequency band, representing improvements of 19.7 dB and 11.5 dB, respectively, over conventional single-MZM configurations. The dual-stage design synergizes TFLN’s high electro-optic coefficient with broadband response, yielding 60 GHz chip-level 3 dB electro-optical (EO) bandwidth, 30 GHz packaged 3 dB bandwidth, and effective operational bandwidth exceeding 60 GHz. This ultra-linear compact modulator provides a scalable solution for high-speed optical communication systems, effectively bridging the technological gap between integrated microwave photonics (MWP) and stringent linearity requirements.