The research in our lab is based on optical microresonators. These chip-based, micro/milli-meter scale photonic devices are able to confine light for up to several hundreds of nanoseconds, effectively compressing several tens of meters of light beam into microscale structures. This results in high circulating optical power inside the resonator, which makes the optical microresonator a popular platform for studying new physics and photonics applications.
In our group, we are particularly interested in studying microresonator-based optical frequency combs (microcombs). Microcombs use Kerr nonlinearity to convert a single wavelength, continuous wave pump laser into hundreds of laser lines with equally spaced frequencies (called frequency comb). Microcombs leverage integrated photonics to miniaturize the Nobel prize winning comb technology, which could revolutionize the instrumentation in spectroscopy, metrology, navigation, and astronomy.
Three silica microresonators on a silicon chip.
Integrated Silicon Nitride microresonators.
Stokes Soliton: Discovery of a new type of optical soliton wave that travels in the wake of other soliton waves, feeding off of the energy of the other wave. Despite decades of study, this is the first soliton that behaves in a dependent—almost parasitic—manner.
(Photo credit: Qifan Yang, Dr. Ki Youl Yang, Caltech)
Light bullet on a chip!
A silica microresonator converts a single wavelength pump laser into thousands of equal distance mode locked laser lines. Numerous applications could benefit from this soliton frequency comb, including optical clock, super GPS, astronomical calibration and etc. (photo credit: Qifan Yang, Caltech)
Exoplanet! We built a laser frequency comb to assist measuring the stellar wabbling caused by its planets. The velocity of the stars that are thousands of light year away from us, can be measured down to 30 cm/s accuracy. The system was tested in NASA IRTF telescope and W.M. Keck Observatory, Hawaii.
Electro-optic frequency divider.
Using a breadboard-sized frequency comb system, we stabilize microwave signals in the range of gigahertz, or billions of cycles per second—using a pair of laser beams as the reference on a chip. This new technology was referred as electro-optical frequency division. (photo credit: Dr. Jiang Li)