Generally, to predict dispersion profile, one usually simulates distribution of eigenmodes in microresonator, which is done by solving system of Maxwell equations in commercial softwear like COMSOL or ANSYS (via Finite Elements Method). For high frequencies red and blue curves are almost the same. For the red curve comb would vast until until 230 THz on the low frequency side, while for hybridized mode it would go 190 THz. On the figure above one can observe extension of the Dint (Mode deviation) profile, due to locally induced anomalous dispersion (around 220THz). Red and pink Dint profiles correspond to resonators alone (when only one of them exists and is measured), while the blue profile refers to hybridised mode which exists only in the system of two resonators and propagates simultaneously in both of them. The figure below represents the example of dispersion engineering with 2 concentric resonators. The extension happens due to the mode hybridization between two resonators at a given range of frequencies, where one can effect the dispersion. New approaches has been proposed: combining several resonators to locally induce anomalous/normal dispersion thus extending overall Dint profile (see for example: ).įigure demonstates conventional (a) and advanced (b) resonator geometries. However, this is already well established technique, which has already met its limit. If |Dint| is significantly more than 0, which means that the mode is far from the corresponding microresonator resonance, the comb substantially decays (see the figure above for example).Ĭonventional way to engineer dispersion is to play with geometrical parameters of the single waveguide. Generally, we want Dint (see figure above) to be slightly > 0 and very broad, thus the comb is flat and broad. The dispersion profile (Dint vs frequency) determines the spectrum of the comb one can achieve in microresonator. It appears that one of the key conditions for comb generation - is an anomalous dispersion (where the distance between two consecutive resonances of the resonator increases with increasing optical frequency, D2>0 (on the figures) ).

The former can be obtained by increasing the Q-factor of the microresonator, while the latter one is a problem of dispersion engineering, where the geometry of the microresonator is designed in a special way to guide the light. However, this nonlinear process requires high optical confinement of the light, so that non-linear processes can play a significant role, and an appropriate dispersion of the light modes in microresonator. Recently, FC were discovered in microresonators, where they can be generated due to the optical parametric oscillations, i.e four-wave mixing. We aim for advanced dispersion engineering design of microresonators to achieve broad (ideally octave-spanning) frequency combs.įrequency comb is an array of equidistant spikes in frequency domain. Prediction of geometrical parameters given a dispersion curve. Reverse Engineering in Dispersion Engineering

Reverse dispersio in light