photonic frequency comb modeling
Photonic frequency combs are a very powerful technology to convert a bright, nearly monochromatic source like a laser into a fully-tunable optical source that spans a broad (yet adjustable) range of wavelengths. In principal, these sources have all the capabilities that one might desire, such as adjustable bandwidth, intensity, coherence, cross-correlation, and modulatability. The discovery of this unique technology led to a Nobel Prize awarded in 2005 to John L. Hall and Theodor W. Hänsch "for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique.”
Nonetheless, challenges remain with optical combs. Significantly, high-performance optical combs now available commercially are large, bulky, and expensive, which generally constrains widespread deployment outside the laboratory. Incorporating these structures into on-chip micro-resonators adds two key features: small size / portability, as well as compatibility with CMOS processes and circuits. The goal of our project was to facilitate the process of integrating optical combs with CMOS-compatible manufacturing and circuits by creating a MAPP-compatible compact model.
This project has led to the development of a compact model for the operation of a microring resonator, which was validated against finite-difference time-domain simulations, and shown to run 720 times faster . Excellent agreement was observed in both the frequency and the time domain; features matching well include the beat frequencies and associated range of generated wavelengths . The primary mismatch occurs at short times during the transient pulse, when the greatest nonlinearities are present. These errors can be systematically by including additional coupling terms for self- and cross-phase modulation in the compact model, at the expense of slightly longer computational times.
This compact model was then subsequently released as an open-source tool with a graphical user interface . By combining the recently developed pilot MAPP-opto module with the nonlinearities embedded in the developed model, it is possible to design a programmable optical timing circuit, with possible applications in highly accurate time-keeping and optical metrology (e.g., detection of trace impurities) in small devices.
The main impact of this work to date is to demonstrate that fairly complex systems such as photonic frequency combs can be treated in a computationally tractable way through compact modeling, which can pave the road toward integration into other systems. All the code developed for this project is attached for further development and analysis by our group as well as other interested parties. Please feel free to contact me with any questions or recommendations via pbermel at purdue dot edu.
 Roman Shugayev and Peter Bermel, "Time-domain simulations of nonlinear interaction in microring resonators using finite-difference and coupled mode techniques," Optics Express 22, 19204-19218 (2014).
 Yujie Guo, Peter Bermel, and Roman Shugayev "Generation Model with Coupled Mode Theory," (2015). URL: https://nanohub.org/resources/cmtcomb3. DOI: 10.4231/D38911R9Q.