Hybrid integrated III-V / lithium niobate dual-polarization coherent optical transmitter

Driven by the increasing demand for data throughput and integration density in optical interconnects, thin-film lithium niobate (TFLN) based transmitters have become highly desirable for high-speed optical communication. Here, we demonstrate a C-band dual-polarization coherent transmitter enabled by hybrid integration of a tunable external cavity laser and a dual-polarization in-phase quadrature (DPIQ) modulator. The laser is formed by TFLN micro-ring resonators and a Sagnac loop reflector in combination with a reflective semiconductor optical amplifier (RSOA), which exceeds a 55 dB side-mode suppression ratio, ∼ 6.33 kHz intrinsic linewidth, and ∼ 30 nm tuning range. The DPIQ modulator exhibits ∼ 90 GHz EO bandwidth and ∼ 2.3 V half-wave voltage. The transmitter supports 60 Gbaud DP-QPSK modulation.