In this talk I will review advances in optical frequency comb implementations of so-called electro-optical (EO) frequency combs, based on phase and intensity modulation of a stable carrier. Stable frequency comb operation spanning over an octave and subsequent self-referencing was recently achieved by the NIST group (Beha et al., 2017). This inspires different implementations of EO frequency combs, including fiber based systems and photonic integrated circuit approaches. Electro-optical combs offer attractive possibilities compared to other approaches such as high tunability of repetition rate.
Our approach includes the use of a low-noise fiber laser as carrier that is stabilized to a molecular transition in an isotopically pure acetylene cell achieving an absolute stability with an uncertainty of 5 kHz. This inherent stability leads, among others, to simplification of the feedback needed to achieve a frequency comb locked with stable operation, limiting the need for advanced clock references.
These research efforts promise simplification and ultimate stability of frequency combs, important for applications where absolute frequency determination is necessary, such as metrology purposes and precise spectroscopy.
[Beha et. al, Optica Vol. 4, Issue 4, pp. 406-411 (2017)]Biography
Andreas Næsby Rasmussen is a scientist at the Danish National Metrology Institute (DFM A/S) in Hørsholm, Denmark, exploring novel optical frequency comb implementations and technologies for spectroscopy, calibrations and metrology purposes.
He obtained his Ph.D. degree in experimental quantum optomechanics from the Niels Bohr Institute, Copenhagen University in 2013. After his Ph.D. he joined the University of Queensland (Australia) as a postdoctoral fellow working on experiments towards plasmonically enhanced optomechanics using optical whispering gallery resonators. From 2016-2018 he worked on new laser spectroscopic methods for characterizing the impurity content of deep ice cores from Greenland and developed new electro-opto-mechanical systems at Aarhus University.