Stable optical frequency combs based on ultrafast lasers have revolutionized measurements of optical frequencies. These combs, when stabilized to the world's best microwave and optical standards, have been used for many elegant investigations of fundamental constants. In addition, they have been employed for the more practical applications of determining readily accessible wavelength standards. Ultimately, everyone may have a comb-based optical frequency synthesizer in his or her laboratory or factory. Indeed, this research will contribute to making that dream a reality. Portable combs will require low-cost, portable optical frequency references for many applications. Such references are also needed to calibrate other optical frequency measurement devices currently employed in industry.
The PI proposes to develop novel gas cells based on a hollow, low loss optical fiber, called photonic bandgap (PBG) fiber. PBG fiber cells will be much more robust than their glass vapor cell counter-parts. In addition, narrower absorption features can be observed in these cells, because light can be confined at high intensities with very low losses in the core of these fibers, facilitating saturated absorption spectroscopy on the molecules confined within. Narrower line widths will lead to higher accuracy. These portable, fiber-based standards have the potential for accuracies of 10 - 100 kHz. By stabilizing a comb to these references, we may potentially create radio frequencies more stable than those of a quartz oscillator.
Broader Impacts: The telecommunications industry currently relies on vapor cells with absorption features ~ 1 GHz wide to calibrate wavelength measuring devices. The robust nature of the PBG fiber cells proposed here will increase the range of devices into which these molecular references can be included. Furthermore, the higher accuracy of these standards will fill the increasing demands brought on by increasingly dense wavelength channel packing. Combs stabilized to these references may be incorporated in lidar, or as a stable, portable rf source. The educational impacts will also be significant. Two graduate students and an undergraduate would be employed in the research. The PI will incorporate aspects of this research in teaching at the introductory, advanced undergraduate, and graduate levels. The PI has already become involved in outreach programs at Kansas State University that target high school and 6th grade girls, and is working to recruit a talented minority college freshmen to the lab.
