Advanced characterization techniques of photonic devices with frequency combs

Abstract: Integrated photonics has witnessed remarkable progress in the last decades. Measuring photonic devices in amplitude and phase provides insight into their performance. Swept wavelength interferometry is a prominent technique for the broadband characterization of the complex response. It leverages continuous advances in rapidly tunable laser sources but is prone to systematic errors associated with frequency calibration. This thesis focuses on the non-destructive measurement of ultralow-loss photonic devices using swept wavelength interferometric technique. We overcome issues associated with nonlinear tuning by calibrating the frequency of the laser on the fly with the aid of a frequency comb. We apply the concept to diverse components of relevance including microresonators and spiral waveguides. This technique enables diagnosing waveguides for the loss and potential defects and is instrumental in optimizing device fabrication ecosystems. The measured phase response of microresonators allows for untangling the coupling condition and provides insight into microresonator-waveguide systems. The later part of this thesis covers the linear (stepped and multi-heterodyne) methods for spectral and temporal characterization of frequency combs. The linear heterodyne method provides unprecedented sensitivity and bandwidth range of measurement. In addition, we provide an overview and comparative assessment of the state-of-the-art in the field.