Dokument: Cryogenic silicon resonators as stable ultra-low-drift frequency references
| Titel: | Cryogenic silicon resonators as stable ultra-low-drift frequency references | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=59690 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20220620-092649-2 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Wiens, Eugen [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Schiller, Stephan [Betreuer/Doktorvater] Prof. Dr. Görlitz, Axel [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 530 Physik | |||||||
| Beschreibung: | This work describes all stages of the development of three silicon mono-crystal optical resonators and
their operation in the deep cryogenic regime at 1.5 K in a pulse-tube cryostat with an attached Joule- Thomson stage and active stabilization of tilt. The first system, consisting of a horizontally-oriented resonator with a length of 25 cm, was mounted inside a copper frame with a ten-point support configuration and operated uninterrupted for three years at the temperature of 1.5 K, except for short maintenance intervals of the cryostat. During this time the sensitivity of the resonator to temperature, vibrations, tilt, and optical power was characterized. The resonator possesses an extremely low coefficient of thermal expansion of 1.4×10^−13/K at the temperature of 1.5 K. Additionally, the thermal response was investigated in the temperature range from 1.5 K to 23.8 K, and a zero-crossing of sensitivity with a temperature derivative equal to −6×10^−10/K^2 was found at a temperature of 16.8 K. The mean sensitivity to vibrations along all three spatial directions was measured using the eigenvibrations of the pulse-tube in the frequency range up to 200 Hz. We found it to be on the order of 1×10^−8/g. The frequency stability of a 1.5 μm laser locked to the TEM00 mode was measured against a hydrogen maser corrected for frequency drift using a GNSS atomic reference. It is comparable to the stability of a hydrogen maser for the integration times between 1 s and 10 000 s. We also monitored the long-term drift of the resonator. The most stable half-year interval displayed the lowest drift ever measured with optical resonators, < 1.4×10^−20/s in fractional terms. After evaluation of all sensitivities, the system was shown to have the potential to reach instabilities of 1×10^−16 at median integration times with a short-term instability limited by vibrations inside the cryostat together with a high vibration sensitivity of the resonator. To minimize the influence of the pulse-tube-generated vibrations we designed a 5 cm long, vertically oriented silicon optical resonator installed inside a copper frame using three support points. Designed for low acceleration sensitivity, this system displayed a sensitivity of 133 kHz/g (6.9×10^−10/g). Besides a zero crossing of temperature sensitivity at 17 K, this resonator exhibits an additional zero crossing of thermal sensitivity at 3.5 K with a temperature derivative of 8.5×10^−12/K^2. Locking a 1.5 μm laser, prestabilized to a room-temperature ULE resonator to the silicon resonator, the latter was found to provide an optical frequency with instability comparable to that of a hydrogen maser and reached a minimum frequency instability of 2×10^−15 at 1000 s integration time. We estimate that in an optimized, low-vibration cryostat the resonator should reach an instability of 1×10^−15 at 100 s. The long-term frequency drift was found to be sensitive to the intensity of the laser wave used for the interrogation and the duty cycle. By minimizing the intensity to 100 nW and keeping the duty cycle at 30% we could reduce the drift rate to 49(4) μHz/s (< 3×10^−19/s). With further reduction of intensity, this feature could allow to null the frequency drift rate. Results obtained with the 5 cm long resonator allowed to build and install a 190 cm long resonator inside a Leiden Cryogenics cryostat equipped with a home-built two-stage vibration isolation system, which reduces vibrations at the experiment by a factor of 40. This system is still an ongoing project, that has already shown hydrogen-maser-matched performance, long-term frequency drift on the order of 1×10^−20/s, and vibration sensitivity of 1×10^−10/g. Using the frequency stability of the 25 cm long horizontal resonator we search for hypothetical violations of Lorentz Local Invariance (LLI) and Local Position Invariance (LPI) in the ratio of the frequency of a cryogenic silicon optical resonator and a hydrogen maser. The analysis of LLI was done within the Robertson-Mansouri-Sexl kinematic test theory, assuming the Cosmic Microwave Background (CMB) as the reference frame. The violation parameter is PKT = (0.9±1.1) ·10^−5. The analysis of LPI is done by a null redshift test, using the natural motion of the Earth in the sun’s gravitational potential. We obtain the violation parameter β = (1.0±1.1) ·10^−5. The 1 σ upper limit for |β| is better than the best previous result obtained with an electromagnetic resonator. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Physik » Experimentalphysik | |||||||
| Dokument erstellt am: | 20.06.2022 | |||||||
| Dateien geändert am: | 20.06.2022 | |||||||
| Promotionsantrag am: | 21.01.2021 | |||||||
| Datum der Promotion: | 24.06.2021 |
