ECNU sets milestone in optical frequency divider research


A team led by Prof. Ma Longsheng from the State Key Lab of Precision Spectroscopy in ECNU has made a milestone achievement in realizing an optical frequency divider (OFD) with division uncertainty at the unprecedented 10-21 level after years of unremitting efforts.

The team led by Prof. Ma set milestone in optical frequency divider research.

Published recently in the National Science Review, China’s first comprehensive scholarly journal in English, the progress sets the stage for applying OFD to several frontiers of science and technology: from transfer of light coherence across the span of electromagnetic bands to comparison of optical clocks based on different atomic species at different frequencies.

The division uncertainty induced by the OFD, which can accurately divide an optical frequency with a preset arbitrary ratio to several other wavelengths, is therefore three orders of magnitude better than the most accurate optical clocks, promising optical frequency division without degrading the performance of optical clocks. The researchers hope this type of optical frequency divider will be also instrumental in precision measurement.

Prof. Ma attends 1994 Nobel Prize award ceremony with the invitation of John L. Hall (Right).

During division, the coherence and frequency accuracy of the input light is faithfully transferred to the output light. The demonstrated performance of the optical frequency divider supports frequency division of the most stable and the most accurate optical signals.

Every drop of sweat counts - more than 30 years of Ma’s hard work paid off.

Ma’s odyssey began in the 1980s when he obtained a chance to pursue advanced studies in precision and ultrasensitive spectroscopy in the United States in 1981. During the stay, he won a U.S. patent for an invention with him as the leading inventor. After finishing the study, he declined the U.S. side’s request to stay and returned to China, unswerving in his resolve to bring China’s lagged-behind laser spectrum research on par with that of the developed countries.

Prof. Ma and his team members

The hard times in the beginning years did not deter Ma and his colleagues, who managed to remodel the then lab in ECNU, predecessor of the State Key Lab of Precision Spectroscopy, by self-designing and building equipment and analytical instruments in spite of fund shortage.

Ma shifted his focus to the research of femtosecond optical frequency comb after 1999. In 2013, a team led by Ma and Bi Zhiyi partnered with US National Institute of Standards and Technology (NIST) and International Bureau of Weights and Measures (BIPM) to conduct international comparative research on four optical frequency combs, which accomplished record fractional frequency instability and uncertainty at the 10-19 level. The result was lauded by an internationally renowned institute to be “unprecedented” and “paved the way for development of next-generation optical atomic clocks”.

The data was cited in the announcement of 2005 Nobel Prize in Physics. John L. Hall and Theodor W. Hansch, co-winners of the Nobel Prize in Physics in 2005, praised Ma’s research in their speeches given at the award ceremony, which Ma and his wife attended at the invitation of Hall.

Prof. Ma wins the Rabi Award.

Ma won the second prize of China’s National Natural Science Award in 2006 and four years later, he received the Rabi Award from IEEE-UFFC-IFCS. Rabi Award, founded in 1983 and named after Isidor Isaac Rabi, Nobel Prize winner in 1944, is to recognize outstanding contributions related to the fields of atomic and molecular frequency standards, and time transfer and dissemination. So far, more than 30 scientists have won the award, four of whom are Nobel laureates.

Other achievements of Ma and his team included a low-noise optical frequency synthesizer, which facilitates the application of optical clocks and precise spectrum research. The finding was carried by the Applied Physics Letter in 2016, which was acclaimed by experts as a discovery “realizing a long-cherished dream of atomic and optical scientists”.


East China Normal University