Past Research
High-Stability Frequency Distribution over Optical Fiber Network
With the higher frequency stability ~1x10^(-15) at 1 s now offered by optical atomic clocks (due in part to contributions from FFCs), standard methods of time/frequency transfer (GPS, two-way satellite transfer) that have higher instabilities [~1x10^(-12) at 24 hours] are no longer adequate to maintain this high stability. Moreover, new requirements for a distributed timing signals with ultra-low timing jitter have emerged for applicationsf ranging from long baseline antennae arrays for astronometric observations to linear accelerator facilities. We developed a set of techniques to transfer both optical and RF frequency standards down installed optical fiber networks over ~5km length scales Instabilities for transferring optical frequency standards were lowered to ~6x10^(-18) at 1 s and microwave frequency standards to ~7x10^(-15) at 1s with a total jitter of 16 fs in the latter. This level of performance is now suitable for comparing optical frequency standards in remote locations. Here at UBC, we developed a new all-optical detection technique that lowered the jitter to 40 attoseconds. Since we started this research program, its importance in national and international metrology programs has been recognized as similar research efforts have now been initiated worldwide in the UK (National Physical Laboratory) France (BIPM), Germany (PTB), and Japan (AIST).
Fiber laser Femtosecond Frequency combs
The early demonstrations of femtosecond frequency combs (FFC) relied primarily on Ti:sapphire lasers, it was of high interest to develop a comparable system using optical fiber technology. Following my arrival at UBC, I continued my work in FFCs by developing such fiber-based systems. In collaboration with Dr. Pierre Dube, Dr. John Bernard, and Dr. Alan Madej of the Frequency and Time group at Institute for National Measurement Standards (INMS) NRC-CNRC (Ottawa), my lab sent two such FL-FFCs to the IMNS in Ottawa. After verifying their capabilities by comparing them to the NRC’s traditional laser-based comb system, we completed an extensive series of new measurements on acetylene-d absorption lines to provide an frequency reference atlas in the 1550 nm region for telecom wavelengths. In addition, a key characteristic of our newly developed FL-FFC systems is their capability to run continuously for several days. Using this feature, we used these FL-FFCs as a clockwork to perform long term (7+ days) evalutions of NRC's Sr+ ion frequency standard against a Cs fountain clock to study hitherto unresolved systematic errors.
