High Energy Ultrashort-Pulse Microresonator Sources

University Of Rochester, Rochester NY

Investigators

Abstract

Laser sources that can generate ultrashort pulses in time are highly desirable for applications including precision machining, ocular surgery, wavelength conversion, deep-tissue imaging, and all-optical clocks. The associated broad bandwidth from these sources is also ideal for spectroscopy, telecommunications, and distance ranging applications. Current short-pulse laser technology is very powerful but is restricted in size, cost, wavelength, and pulse performance by the requirement of a carefully arranged laser gain medium. More recent microresonator devices, on the other hand, operate without this gain limitation, but suffer from very low pulse energies, which limits their wider applicability. The objective of this research is to improve the energy performance of microresonator sources by up to a thousand times to develop highly adaptable sources of ultrashort pulses of light. In addition to significantly improving the performance of current microresonator applications in telecommunications and spectroscopy, this research can enable cheap, simple, small, light, and wavelength-versatile microresonator sources that can supplant standard pulsed lasers for traditional ultrashort-pulse applications including bio-imaging, frequency conversion, and all-optical clocks. Beyond technological impact, this project will train two PhD students in an area of large technological importance at the interface of nano-technology, ultrafast nonlinear optics and advanced optical technologies, and the PIs will integrate this important platform into the regular curriculum as well as into the extra-curricular optics summer-school program at the University of Rochester. Technical description Chip-based frequency-comb sources have proven to be a valuable resource for applications including spectroscopy, telecommunications, ranging, and signal processing. However, current microresonator sources have low single-pulse efficiencies and very low energies, at the femtojoule level. Applications currently require external amplification, limiting the source bandwidth and negating the benefits of an on-chip source. The objective of this research is to develop versatile on-chip devices for generating frequency-combs and ultrashort pulses with high efficiencies and up to a thousand times higher energies than the state-of-the-art. The energy of microresonator solitons is limited by the amount of optical nonlinearity that can be compensated by dispersion before the soliton destabilizes. We will experimentally demonstrate how this limit can be engineered through loss-engineering in strongly over-coupled cavities. We will develop normal dispersion cavities with integrated spectral filters to generate a type of novel chirped-pulse soliton that was recently shown by the PI to support very high energies in related fiber cavities. Successful implementation of these techniques, in addition to improving the performance of current microresonator applications significantly, will enable cheap, simple, small, light, and wavelength-versatile microresonator sources that can supplant mode-locked lasers for traditional ultrashort-pulse applications including bio-imaging, frequency conversion, and frequency-comb self-referencing. Beyond technological impact, this project will train two PhD students in an area of large technological importance at the interface of nano-technology, ultrafast nonlinear optics and advanced optical technologies, and the PIs will integrate this important platform into the regular curriculum as well as into the extra-curricular optics summer-school program at the University of Rochester. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.