Microresonator-based soliton generation promises chip-scale integration of optical frequency combs for applications spanning from time keeping to frequency synthesis. Access to the soliton repetition rate is a prerequisite for those applications. While miniaturized cavities harness Kerr nonlinearity and enable terahertz soliton repetition rates, such high rates are not amenable to direct electronic detection. Here, we demonstrate hybrid Kerr and electro-optic microcombs using a lithium niobate thin film that exhibits both Kerr and Pockels nonlinearities. By interleaving the high-repetition-rate Kerr soliton comb with the low-repetition-rate electro-optic comb on the same waveguide, wide Kerr soliton mode spacing is divided within a single chip, allowing for direct electronic detection and feedback control of the soliton repetition rate. Our work establishes an integrated approach to electronically access terahertz solitons, paving the way for building chip-scale referenced comb sources.
Microresonator solitons are critical to miniaturize optical frequency combs to chip scale and have the potential to revolutionize spectroscopy, metrology and timing. With the reduction of resonator diameter, high repetition rates up to 1 THz become possible, and they are advantageous to wavelength multiplexing, coherent sampling, and self-referencing. However, the detection of comb repetition rate, the precursor to all comb-based applications, becomes challenging at these repetition rates due to the limited bandwidth of photodiodes and electronics. Here, we report a dual-comb Vernier frequency division method to vastly reduce the required electrical bandwidth. Free-running 216 GHz “Vernier” solitons sample and divide the main soliton’s repetition frequency from 197 GHz to 995 MHz through electrical processing of a pair of low frequency dual-comb beat notes. Our demonstration relaxes the instrumentation requirement for microcomb repetition rate detection, and could be applied for optical clocks, optical frequency division, and microwave photonics.
more » « less- Award ID(s):
- 1842641
- NSF-PAR ID:
- 10181800
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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