Phononic Frequency Combs

Optical frequency combs, by its manifestation as a frequency ruler, has revolutionized optical frequency metrology and spectroscopy. Only very recently, the phononic analogue of such frequency combs was experimentally demonstrated1 in a microelectromechanical resonator confirming predictions made by numerical simulations of a Fermi-Pasta-Ulam system2. This initial experimental demonstration was followed up in further studies3-5 where variants of phononic frequency combs have been systematically studied using similar device testbeds over a range of drive conditions. The generation of phononic frequency combs in each case is inherently related to nonlinear modal coupling in such structures with exquisite control of geometry, material properties and conditions required for engineering application. In addition to the general scientific interest, phononic frequency combs also enable a unique approach to tracking the resonant frequency of a micromechanical resonator without an external feedback loop with the potential for improvements in frequency stability compared to conventional feedback oscillators6.
1 PRL 118 3 033903 2017
2 PRL 112 7 075505 2014
3 APL 111 064101 2017
4 arXiv:1704.08008
5 arXiv:1708.07563
6 arXiv:1710.07058