Folded electro-optical modulators operating at CMOS voltage level in a thin-film lithium niobate foundry process

Integrated electro-optical modulators with small footprints and low half-wave voltage are essential for applications requiring high integration density and low power consumption. Modulators based on thin-film lithium niobate technology have been proven to perform excellently, both in terms of low voltage and high bandwidth operation. However, achieving half-wave voltages of ∼1 V, which allows to directly drive the modulator with CMOS circuits, typically requires long structures. Folding the device is a possible approach to achieve a CMOS-compatible voltage level in a compact design. Yet, this method requires meticulous design and advanced manufacturing technology. To achieve large scale deployment of this technology, it is imperative to further develop thin-film lithium niobate photonic integrated circuits manufacturing. Here, we address these requirements and report folded electro-optical modulators, operating at 1550 nm in TE polarization, with half-wave voltage as low as 0.9 V or bandwidths up to beyond 40 GHz in a compact 5 mm × 5 mm chip fabricated in CSEM's open-access foundry process using standardized process design kit components.