Scalable manufacturing of integrated optical frequency combs

Photograph showing hundreds of semiconductor lasers and silicon nitride microresonators (credit: Chao Xiang, UCSB) - A collaboration between EPFL and UCSB has developed a long-anticipated breakthrough, and demonstrated CMOS technology - used for building microprocessors and memory chips - that allows wafer-scale manufacturing of chip-scale optical frequency combs. Optical frequency combs consist of light frequencies made of equidistant laser lines. They have already revolutionized the fields of frequency metrology, timing and spectroscopy. The discovery of ''soliton microcombs'' by Professor Tobias Kippenberg's lab at EPFL in the past decade has enabled frequency combs to be generated on chip. In this scheme, a single-frequency laser is converted into ultra-short pulses called dissipative Kerr solitons. Soliton microcombs are chip-scale frequency combs that are compact, consume low power, and exhibit broad bandwidth. Combined with large spacing of comb "teeth", microcombs are uniquely suited for a wide variety of applications, such as terabit-per-second coherent communication in data centers, astronomical spectrometer calibration for exoplanet searches and neuromorphic computing, optical atomic clocks, absolute frequency synthesis, and parallel coherent LiDAR.