Photonic Integration

Project on microresonator comb generation (This project is funded by Science Foundation Ireland under their collaboration programme with the National Science Foundation of China) in collaboration with Professor Wei-Hua Guo of Huazhong University of Science and Technology).

Over the past decade, applications of optical frequency combs (OFCs) have rapidly grown across diverse areas of science and engineering, including chemical sensing, optical clock, distance ranging, and as a source for wavelength-division multiplexing in coherent communications.

Recently, nonlinear optical microresonators with various materials such as silica, Si3N4, AlN, and LiNbO3 were demonstrated to successfully generate optical combs. Compared with femtosecond lasers, the chip-based microresonator comb source have the advantages of being very compact, portable, robust with fully integrated form factors, which make them suitable for a wide range of applications in different fields.

We are developing high Q microresonators with materials Si3N4, AlN, and LiNbO3 using near infra-red single mode lasers as the pump to then generate the optical comb. We are interested to miniaturize the whole setup to chip-scale by integrating different chips on the same platform with comprehensive control and effective feedback. Finally, a highly accurate optical frequency source with low cost will be developed, which are easily available for applications such as a chip-scale optical clock, high spectral efficiency optical communications, and LiDAR. Suitable optical pumping sources include the slotted lasers shown above.




(a)-(b) The SEM images of an AlN microring and (c) measured transmission curve. (d)-(f) for LiNbO3 material. SEM images for (d) microring integrated with a pulley waveguide and (e) grating coupler. (f) Measured resonance of the ring with a Q factor of 1.2 × 105. 




 SEM images of LiNbO3 ring and waveguide. The sidewall roughness needs to be improved.


We have recently observed comb formation in an AlN ring resonator. Pumping at 1559.47 nm with Q value of 0.54 x 106 , with an estimated power of 300 mW in the resonator. 




SEM images of LiNbO3 ring and waveguide. The sidewall roughness needs to be improved.