Highly linear electro-optic modulators are key components in analog microwave photonic links, offering on-chip direct mixing of optical and RF fields. In this work, we demonstrate a monolithic integrated Michelson interferometer modulator on thin-film lithium niobate (LN), that achieves linearized performance by modulating Bragg grating reflectors placed at the end of Michelson arms. The modulator utilizes spiral-shaped waveguide Bragg gratings on Z-cut LN with top and bottom electrodes to realize extensive reflectors, essential for linearized performance, in a highly integrated form. Optical waveguides are realized using rib etching of LN with precisely engineered bottom and top cladding layers made of silicon dioxide and SU-8 polymer, respectively. The compact design fits a 3 mm long grating in an 80 µm × 80 µm area, achieving a broad operating bandwidth up to 18 GHz. A spurious free dynamic range (SFDR) of 101.2 dB·Hz2/3 is demonstrated at 1 GHz, compared to 91.5 dB·Hz2/3 for a reference Mach-Zehnder modulator fabricated on the same chip. Further enhancement in SFDR could be achieved by reducing fiber-to-chip coupling loss. The proposed demonstration could significantly improve the linearity of analog modulator-based integrated optical links.
|Original language||English (US)|
|Number of pages||16|
|State||Published - Oct 24 2022|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics