We have investigated parametric seeding of a microresonator frequency comb (microcomb) by way of a pump laser with two electrooptic-modulation sidebands. We show that the pump-sideband spacing is precisely replicated throughout the microcomb's optical spectrum, and we demonstrate a record absolute line-spacing stability for microcombs of 1.6 x 10(-13) at 1 s. The spectrum of a microcomb is complex, and often non-equidistant subcombs are observed. Our results demonstrate that parametric seeding can not only control the subcombs, but can lead to the generation of a strictly equidistant microcomb spectrum. (C) 2013 Optical Society of America
Mechanical Control of a Microrod-Resonator Optical Frequency Comb
We report on the stabilization of a microresonator-based optical frequency comb (microcomb) by way of mechanical actuation. These experiments use novel CO2-laser-machined microrod resonators, which are introduced here and feature optical Q >= 5 x 10(8), less than 1 minute processing time, and tunable geometry. Residual fluctuations of our 32.6 GHz microcomb line spacing reach a stability level of 5 x 10(-15) for 1 s averaging, thereby highlighting the potential of microcombs to support modern optical-frequency standards. Furthermore, measurements of the line spacing with respect to an independent frequency reference reveal stabilization of different spectral slices of the comb with a <0.5-mHz variation among 140 comb lines spanning 4.5 THz. Together, these results demonstrate an important step in the development of microcombs, namely, that they can be fabricated and precisely controlled with simple and accessible techniques.
Laser-machined ultra-high-Q microrod resonators for nonlinear optics
Optical whispering-gallery microresonators are useful tools in microphotonics and non-linear optics at very low threshold powers. Here, we present details about the fabrication of ultra-high-Q whispering-gallery-mode resonators made by CO2-laser lathe machining of fused-quartz rods. The resonators can be fabricated in less than 1 min and the obtained optical quality factors exceed Q = 1 x 10(9). Demonstrated resonator diameters are in the range between 170 mu m and 8mm (free spectral ranges between 390 GHz and 8 GHz). Using these microresonators, a variety of optical nonlinearities are observed, including Raman scattering, Brillouin scattering, and four-wave mixing.
Mid-infrared optical frequency combs at 2.5 µm based on crystalline microresonators
Christine Y. Wang,
Tobias Herr,
Pascal Del'Haye,
Albert Schliesser,
Johannes Hofer,
Ronald Holzwarth,
T. W. Hänsch,
Nathalie Picqué,
Tobias J. Kippenberg
Nature Communications
4
1345
(2013)
| Journal
| PDF
Mid-infrared optical frequency combs at 2.5 µm based on crystalline microresonators
Christine Y. Wang,
Tobias Herr,
Pascal Del'Haye,
Albert Schliesser,
Johannes Hofer,
Ronald Holzwarth,
T. W. Hänsch,
Nathalie Picqué,
Tobias J. Kippenberg
The mid-infrared spectral range (λ~2–20 μm) is of particular importance as many molecules exhibit strong vibrational fingerprints in this region. Optical frequency combs—broadband optical sources consisting of equally spaced and mutually coherent sharp lines—are creating new opportunities for advanced spectroscopy. Here we demonstrate a novel approach to create mid-infrared optical frequency combs via four-wave mixing in a continuous-wave pumped ultra-high Q crystalline microresonator made of magnesium fluoride. Careful choice of the resonator material and design made it possible to generate a broadband, low-phase noise Kerr comb at λ=2.5 μm spanning 200 nm (≈10 THz) with a line spacing of 100 GHz. With its distinguishing features of compactness, efficient conversion, large mode spacing and high power per comb line, this novel frequency comb source holds promise for new approaches to molecular spectroscopy and is suitable to be extended further into the mid-infrared.
Kontakt
Forschungsgruppe Pascal Del'Haye
Max-Planck-Institut für die Physik des Lichts Staudtstr. 2 91058 Erlangen
