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In this work, we propose a mode-conversion-based chirped Bragg grating on thin-film lithium niobate (TFLN). The device is mainly composed of a 4.7-mm long chirped asymmetric Bragg grating and an adiabatic directional coupler (ADC). The mode conversion introduced by the ADC allows the chirped Bragg grating operates in reflection without using an off-chip circulator. The proposed device has experimentally achieved a total time delay of 73.4 ps over an operating bandwidth of 15 nm. This mode-conversion-based chirped Bragg grating shows excellent compatibility with other devices on TFLN, making it suitable in monolithically integrated microwave photonics, sensing, and optical communication systems.

In this work, we report a linearity-enhanced dual-parallel Mach–Zehnder modulator (MZM) on a thin-film lithium niobate platform. By setting the optical and electrical splitting ratios at a specific condition, the third-order intermodulation distortions (IMD3) of the child MZMs cancel with each other, whereas the first-order harmonics (FH) reach the maximum. Passive devices instead of thermo-optical switches are used to control the optical power and phase of the child MZMs, which greatly improve the device stability and simplify the operation complexity. To the best of our knowledge, the experimental results show a record-high spurious-free dynamic range on a thin-film lithium niobate platform (110.7 dB·Hz2/3 at 1 GHz). The E-O response decayed about 1.9 dB from 10 MHz to 40 GHz, and the extrapolated E-O 3 dB bandwidth is expected to be 70 GHz. A half-wave voltage of 2.8 V was also achieved. The proposed modulator provides a promising solution for high-bandwidth and low-voltage analog optical links.