Optical frequency combs provide equidistant markers and enable connecting optical to radio frequencies (RF) and vice versa. Today, frequency combs are becoming enabling tools for several applications in metrology and spectroscopy. A new class of Kerr-frequency comb sources, based on parametric frequency conversion in optical silica micro-resonators, has been demonstrated in 2007 by the host group. Over the past years, with the development of new microresonator geometries many novel studies have emerged. This follow-up proposal builds on the recent advances in the field of microresonator-based frequency combs to address novel endeavors:First, the temporal characterization and pulse generation using microresonators. The recently discovered mode-locking mechanism warrants a detailed analysis and exploration; notably it has been observed that the generated frequency combs could be generated Kerr temporal solitons in the resonators. We plan to gain insights into the mechanism of mode-locking and pulse generation, which is presently not understood. In addition we will explore both the generation of ultra-short pulses and of complexe pulse dynamics from crystalline microresonators.Second, we seek to achieve an RF-to-Optical link using a microresonator: So far phase coherent links have been impeded by excess phase noise. Within the context of the discovered low phase noise operation, the latter becomes a realistic endeavor again. We will investigate that routes : using crystalline resonators with external broadening.Third, we plan to demonstrate mid IR frequency combs using crystalline resonator and quantum cascade lasers: Crystalline resonators can due to their anomalous dispersion and large transparency generate low phase noise combs in the mid IR. A natural next step in this context is the combination of a QCL with a crystalline resonator. This would enable a compact, electrically driven optical frequency comb generator in the 3-6 micron wavelength range.