Abstract

The field of frequency metrology was revolutionized by the invention of the optical frequency comb (OFC) [1] in part because it has enabled counting the cycles of light. This opened up many new applications in a wide array of fields from optical clocks, absolute frequency synthesis, tests of fundamental physics, and improved spectroscopy. This technology is based on ultrafast pulses of light which creates an optical frequency comb. Every comb component (f_n) can be characterized by the expression f_n = f₀ + n · f_rep where n is an integer. The two free parameters are the distance between the lines, which are equal to the pulse repetition rate (frep), and the overall offset (f0). Self-referencing of an OFC requires knowing both parameters. Determining f0 is difficult and requires generating a broadband coherent optical spectrum spanning typically at least two-thirds of an octave [2. In 2007 it was discovered that OFCs can be generated in optical microresonators [3, which typically have large spacing between comb lines (10 GHz to 1THz), high power per comb line, and spectrum in the near-infrared or the mid-infrared. Self-referencing a microresonator based frequency comb would enable a phase coherent link from the optical directly to the microwave domain and the ability to count cycles of light. Many new applications [4 could directly benefit from this ranging from astronomical spectrometer calibration, dual comb coherent spectroscopy, Raman imaging, high speed optical sampling and coherent telecommunications. Here we demonstrate for the first time a self-referenced micro resonator based frequency comb [5 using temporal cavity soliton pulses [6.

© 2015 IEEE