14. J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, and M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nature Pho- ton. 4 (1), 37–40 (2009). 15. J. Pfeifle, V. Brasch, M. Lauermann, Y. Yu, D. Wegner, T. Herr, K. Hartinger, P. Schindler, J. Li, D. Hillerkuss, R. Schmogrow, C. Weimann, R. Holzwarth, W. Freude, J. Leuthold, T. J. Kippenberg, and C. Koos, “Coherent terabit communications with microresonator Kerr frequency combs,” Nature Photon. 8 (5), 375–380 (2014). 16. G. Agrawal, Nonlinear fiber optics (Elsevier, 2007). 17. K. Luke, A. Dutt, C. B. Poitras, and M. Lipson, “Overcoming Si$_{3}$N$_{4}$ film stress limitations for high quality factor ring resonators,” Opt. Express 21 (19), 22829–22833 (2013). 18. A. Gondarenko, J. S. Levy, and M. Lipson, “High confinement micron-scale silicon nitride high Q ring resonator,” Opt. Express 17 (14), 11366–11370 (2009). 19. R. Heideman and M. Hoekman, “Surface waveguide and method of manufacture,” US Patent 7,142,759 2 (2006). 20. TriPleX TM is commercially available through LioniX BV, Enschede, The Netherlands.