Various compact integrated photonics devices have been realized on the TFLN platform, such as compact high-performance modulators, polarization management devices, and broadband frequency comb sources. However, the inherent difficulty of lithium niobate in realizing light sources and photodetector poses a challenge for the TFLN integrated photonics platform. As an essential optoelectronic component, an on-chip integrated high-performance photodetector is vital for TFLN photonic integrated chips.

In a new paper published in Light: Advanced Manufacturing, a research team, led by Professor Xiaojun Xie and Lianshan Yan from Key Laboratory of Photonic-Electric Integration and Communication-Sensing Convergence, School of Information Science and Technology, Southwest Jiaotong University, China, has reported a high-speed and high-responsivity modified uni-traveling carrier photodiodes heterogeneously integrated on the TFLN platform. The device exhibits a 3-dB bandwidth of 110 GHz and a responsivity of 0.4 A/W at a wavelength of 1,550-nm wavelength.

The fabrication process was initialized by the dry etching of LN waveguides and passive devices. A hybrid etching approach was followed to form device mesa. After metal plating and lift-off, the chips were diced and polished. Epitaxial layer structure, LN waveguide geometry, and CPW pad geometry were optimized to achieve both large bandwidth and high responsivity.