Raman self-frequency-shift of soliton crystal in a high index doped silica micro-ring resonator [Invited]
Unraveling the complexities of nonlinear dynamics in optical microresonators is an important step towards bringing the revolutionary frequency metrology and synthesis capabilities of optical frequency combs to the chip scale. This manuscript by Zhizhou Lu and colleagues advances the field closer to that goal by investigating two different nonlinear effects simultaneously: the soliton self-frequency shift arising from intra-pulse Raman scattering and the spontaneous temporal ordering of co-propagating, temporally separated pulses known as soliton crystallization. In fact, this manuscript demonstrates that the spectral characteristics of soliton crystals may be leveraged to learn about the optical material’s Raman response, and thereby gives us a new tool for studying nonlinear dynamics in these systems. Equally important, the measurement of the Raman response of the high-index doped silica material presented in this manuscript is important for understanding how to develop this comb platform for applications and for identifying capabilities and limitations of the material (for example, limitations on minimum soliton pulse duration arising from Raman scattering). The results presented here bring us closer to harnessing the immense potential of nonlinear optics in chip-integrated photonic microresonators for a wide variety of applications.