Ultralow-loss and ultrahigh-efficiency O-band LNOI electro-optic modulator enabled by cost-effective PLACE technology

High-performance O-band electro-optic modulators are indispensable for numerous advanced photonic applications. Nevertheless, the simultaneous realization of low insertion loss, low half-wave voltage, and low-cost fabrication in lithium niobate on insulator (LNOI) devices remains a formidable challenge. In this study, an O-band LNOI electro-optic modulator is developed based on the femtosecond laser photolithography assisted chemo-mechanical etching (PLACE) technique. Numerical simulations are carried out to optimize the structural parameters of multimode interferometers (MMIs), spot size converters (SSCs), and electrodes. At the wavelength of 1310 nm, the fabricated device exhibits an ultralow chip-level fiber to fiber insertion loss of 2.2 dB (unpackaged) and 4.6 dB (packaged), an ultralow half-wave voltage-length product (V_π·L) of 1.54 V·cm, an extinction ratio (ER) of 23 dB, and a 3 dB electro-optic bandwidth (S₂₁) beyond 40 GHz. Leveraging the low-cost PLACE fabrication strategy, the proposed device integrates the merits of ultra-low optical loss, high modulation efficiency, and broad operation bandwidth with reliable packaging compatibility. This work provides a feasible pathway for the practical deployment of O-band integrated photonic chips.