Festkörper Interface kohärent zwischen Mikrowellen und Telecom-C Licht
Optik, Quantenoptik und Physik der Atome, Moleküle und Plasmen
Zusammenfassung der Projektergebnisse
In this proposal we investigated possible approaches to bidirectional conversion of coherent fields at optical and microwave frequencies. To this end, we studied spectroscopic properties of rare-earth-doped crystals at sub-Kelvin temperatures, with the aim of finding coherent response to optical and microwave excitation, manifested by normal mode splitting, spin echo, or electromagnetically induced transparency (EIT). Rare-earth-doped crystals are promising for different applications such as (a) optical quantum memories, due to the presence of optical transitions inside telecommunication bands; (b) efficient microwave quantum memories, because of long coherence time of electronic and nuclear spins; (c) circuit QED, due to a large g-factor; (e) microwave-to-optical frequency converters, due to the addressable transitions in optical, microwave and RF frequencies. We needed a special crystal in which the dopant Erbium spin ensemble features a large and uniform gfactor and experiences small inhomogeneous broadening of its optical and spin transitions. As the best candidate we chose isotopically purified LiYF4 for its narrowest optical inhomogeneous broadening. The sub-Kelvin temperature range is very challenging to work at, yet it is very attractive because of the possible applications mentioned above, which are hardly accessible at conventional temperatures above 1.5 K. While not all aims could be reached, our group has succeeded to accomplish some goals and to be pioneers in the field. In particular, we observed coupling of spins to the TE011 mode of a cavity, and we pioneered the OVNA method for spectroscopy of narrow lines in the doped crystals. As a main accomplishment, we observed narrowband EIT in 167Er:LYF. We identified and characterized sources of spectral broadening that inhibited some of the other coherent phenomena. For example, by measuring the temperature and magnetic field dependence of the optical dephasing time we have studied the electronic and nuclear spin dynamics of Er:LYF system at sub-Kelvin temperatures. Nevertheless, it was not possible to diminish the spin linewidth even with crystals having low concentration of 0.001% of Er3+ ions. Apparently, such large inhomogeneous broadening is mainly due to the nuclear spin bath of fluorine ions. In order to attain the super-hyperfine limit of local field fluctuations at weak (∼10 mT) fields, the crystal would have to be cooled down to ∼10 mK. Technically, such deep cooling of the sample may require fabrication of a crystal in the form of a single mode fiber. This is one of the possible future continuations of our work. We also suggested that the presented OVNA method can be used for the on-chip high resolution testing of biomedical and organic substances.
Projektbezogene Publikationen (Auswahl)
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“All-optical control of the silicon-vacancy spin in diamond at millikelvin temperatures”, Phys. Rev. Lett. 120, 053603 (2018)
J. Becker et al.
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“Optical Coherence of 166Er:LYF below 1K”. New J. Phys. 20, 023044 (2018)
N. Kukharchyk et al.
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“Optical vector network analysis of ultranarrow transitions in 166Er3+ : 7LiYF4 crystal”, Opt. Lett. 43, 935 (2018)
N. Kukharchyk et al.
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“Electromagnetically induced transparency in a mono-isotopic 167Er:7LiYF4 crystal below 1 Kelvin: microwave photonics approach”, Opt. Express 28, 29166 (2020)
N. Kukharchyk et al.
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Enhancement of optical coherence in 167Er:Y2SiO5 crystal at sub-Kelvin temperatures
N. Kukharchyk et al.
