An octave spanning chip-based optical ruler
More than a decade ago, the frequency comb technique was developed at the Max Planck In-stitute of Quantum Optics by Professor Theodor W. Hänsch. The new tool has stimulated fun-damental research as well as laser development and its applications because it gave rise to a major increase in the accuracy of measuring optical frequencies. Already a couple of years ago, a team of scientists around Dr. Tobias Kippenberg, formerly Leader of the Max Planck Research Group Laboratory of Photonics and Quantum Measurements at MPQ, who has since then become Associate Professor at the Ecole Polytechnique Fédérale de Lausanne (EPFL), succeeded for the first time in generating optical frequency combs using chip-based quartz glass toroids with diameters on the micrometer scale. Now the scientists made a big step further: their new microresonators produce light over a range of more than an octave and are at the same time precisely tunable (PRL...