Active Low-Voltage Thin-Film Lithium Niobate Electro-Optic Modulator

In recent years, the development of thin-film LiNbO3 (TFLN) waveguides has allowed for increased index contrast resulting in many notable modulator demonstrations including ultralow Vp, modulation speeds approaching THz, and total insertion losses in the realm of 2 dB based on demonstrated propagation and coupling losses. Additionally, the higher index contrast of thin-film LiNbO3 allows for much smaller MFD that is compatible with the modal sizes in typical Si/III-V couplers. While the electro-optic performance of LiNbO3 and high-power handling capability make it a highly desirable material platform for RF photonic systems, Watt-level on-chip optical amplification has not been achieved on the LiNbO3 platform due to its indirect bandgap. Significant work and progress have been developed on integrated optical amplifiers and more recently on the heterogeneous integration of optical amplifiers with silicon photonics as well as LiNbO3. Active devices with high gain have been demonstrated in many PIC platforms. However, due to gain saturation that is inherently related to the limited device cross-section and length in a PIC platform, it is challenging to achieve Watt-level output power even with heterogeneous integration of active materials. Herein, we propose a distributed approach where the light input is first split into multiple channels, each amplified in a gain media, and then recombined on a TFLN chip to achieve the desired high power. In this way, high amplification gain is accomplished in the gain media and high absolute power is achieved on the TFLN chip which is known for its high-power capabilities. On the same TFLN chip, an ultra-low Vp modulator can be integrated to meet the solicited requirements.