Applied Physics Seminar
Scott Diddams is an experimental physicist working in the fields of precision spectroscopy and metrology, nonlinear optics and ultrafast lasers. He received the Ph.D. degree from the University of New Mexico in 1996. From 1996 through 2000, he did postdoctroral work at JILA, University of Colorado. In 1998, Diddams was awarded a National Research Council fellowship to work with Dr. John Hall on the development and use of optical frequency combs. Together with colleagues at JILA, he built the first self-referenced, octave-spanning optical frequency comb and used it to demonstrate carrier-envelope phase stabilized pulses, as well as carry out direct optical to microwave measurements. Since 2000, Dr. Diddams has been a staff member and project leader at the National Institute of Standards and Technology (NIST). With his group and colleagues at NIST, he has continued the development of optical frequency combs and pioneered their use in optical clocks, tests of fundamental physics, novel spectroscopy in the visible and mid-infrared, precision metrology, and ultralow noise frequency synthesis. In recent years, special attention has been given to high repetition rate laser-based and microresonator frequency combs, which are being explored for applications in microwave photonics and astronomy. Dr. Diddams was a recipient of the Department of Commerce gold and silver medals for "revolutionizing the way frequency is measured" as well as the Presidential Early Career Award in Science and Engineering (PECASE) for his work on optical frequency combs. He is a Fellow of the Optical Society of America and the American Physical Society.
The use and manipulation of optical fields allows one to address challenging problems that have traditionally been approached with microwave electronics. Some examples that benefit from the low transmission loss, agile modulation and large bandwidths accessible with coherent optical systems include signal distribution, coherent communications and arbitrary waveform generation. We have recently extended these advantages to demonstrate a microwave generator based on a high-quality factor (Q) optical resonator and a frequency comb functioning as an optical-to-microwave divider. We call this approach optical frequency division (OFD), and it provides a 10 GHz electrical signal with absolute phase noise below -100 dBc/Hz at 1 Hz offset, and a corresponding fractional frequency instability ≤8x10-16 at 1 s. When integrated from 1 Hz to 5 GHz, the timing jitter of such a 10 GHz signal is only a few femtoseconds. By this metric, our photonic microwave generator is 100x more stable than the best electronic microwave oscillators. Beyond a description of the architecture and properties of the photonic microwave generator, I will also discuss fundamental limitations to this approach as well as initial efforts aimed at implementing the OFD technique in a micro-resonator platform.