Breaking voltage-bandwidth limits in integrated lithium niobate modulators using micro-structured electrodes

TL;DR

This paper demonstrates a breakthrough in integrated lithium niobate modulators by using micro-structured electrodes to achieve record low voltage and high bandwidth, enabling sub-volt operation at over 100 GHz.

Contribution

The authors introduce a novel electrode design that overcomes microwave loss limitations, significantly improving voltage-bandwidth performance in thin-film lithium niobate modulators.

Findings

Achieved RF half-wave voltage of 1.3 V at 50 GHz

Maintained 1.8-dB roll-off at 50 GHz

Enabled sub-volt modulators with >100 GHz bandwidth

Abstract

Electro-optic modulators with low voltage and large bandwidth are crucial for both analog and digital communications. Recently, thin-film lithium niobate modulators have enable dramatic performance improvements by reducing the required modulation voltage while maintaining high bandwidths. However, the reduced electrode gaps in such modulators leads to significantly higher microwave losses, which limit electro-optic performance at high frequencies. Here we overcome this limitation and achieve a record combination of low RF half-wave voltage of 1.3 V while maintaining electro-optic response with 1.8-dB roll-off at 50 GHz. This demonstration represents a significant improvement in voltage-bandwidth limit, one that is comparable to that achieved when switching from legacy bulk to thin-film lithium niobate modulators. Leveraging the low-loss electrode geometry, we show that sub-volt modulators with $>$ 100 GHz bandwidth can be enabled.