High-speed, compact and low-crosstalk lithium niobate on insulator 2 × 2 optical switch for on-chip integration

This paper proposes and fabricates a compact lithium niobate on insulator (LNOI) 2 × 2 high-speed electro-optic switch with a folded waveguide structure, aiming to enhance on-chip integration capability. By employing a folded modulation arm configuration, the device length along the optical propagation direction is significantly reduced to approximately 2 mm, relaxing the longitudinal dimension requirement for chip integration. Within the 1560-1580 nm wavelength range, the inter-channel crosstalk is stably maintained below -20 dB, with a minimum crosstalk suppression of -23 dB, demonstrating excellent port isolation performance. Under alternating current (AC) square-wave modulation, the device achieves nanosecond-level high-speed switching with a rise time of 3.8 ns and a fall time of 4.0 ns. Meanwhile, a low half-wave voltage-length product (V_πL) of 2.78 V·cm is obtained, yielding a modulation efficiency comparable to that of state-of-the-art LNOI devices. The proposed switch achieves an effective trade-off between chip-size miniaturization and superior electro-optic performance, providing crucial technical support for the engineering implementation of high-speed, high-density on-chip optical switching systems based on the LNOI platform.