Hybrid Integrated REC-Based Tunable Optical Transmitter via Photonic Wire Bonding

A tunable optical transmitter is demonstrated through hybrid integration of an in-series distributed feedback (DFB) laser array, thin-film lithium niobate (TFLN) Mach–Zehnder modulator (MZM), and single-mode fiber (SMF) using photonic wire bonding (PWB). The total coupling loss introduced by PWB interconnects across the three-component interface is measured to be 5.56 dB. The wavelength tuning is achieved through channel switching across the laser array. Linear chirped sampling is employed in the grating fabrication process to suppress crosstalk between the laser array modes. Multiple equivalent <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pi$</tex-math></inline-formula>-phase shifts (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pi$</tex-math></inline-formula> -EPS) are also introduced to stabilize single longitudinal mode operation. Experiment results indicate that the four-channel laser array exhibits precise 100GHz channel spacing with side-mode suppression ratios (SMSR) exceeding 40dB over a range of bias currents and operating temperatures. The TFLN MZM achieves a 25GHz modulation bandwidth, whose open 25Gb/s non-return-to-zero (NRZ) eye diagrams are successfully observed in both back-to-back and 10km fiber transmission tests. This PWB-based hybrid integration strategy provides a promising solution for next-generation passive optical network (NG-PON2) transmitters, offering significant advantages in balancing coupling efficiency and packaging simplicity.