For some optical atomic clocks, such as a clock based on aluminium ions, the crucial transitions are in the UV spectrum. To generate frequency-stable UV light, the frequency of an infrared laser is first stabilised to a reference cavity. Then the frequency of the IR laser is doubled twice so that UV light is generated.
A key challenge is to transfer the frequency stability from the infrared to the ultraviolet. In their construction of a transportable aluminium ion clock, the researchers of the Cluster of Excellence QuantumFrontiers use non-linear crystals for the twofold frequency doubling. In their setup, the to-be-doubled light passes through each of the crystals only once. Unlike traditional setups, this configuration enables uninterrupted interferometric phase stabilisation of the IR pump laser and thus also of the generated UV light.
"With our setup, we have managed to build a compact, transportable and very phase-stable UV laser for the clock transition of the aluminium ion. In the future, this will allow us to interrogate the clock transition for a longer period of time and to operate the aluminium ion clock at different locations," says doctoral student Benjamin Kraus, responsible for the construction and commissioning of the laser system.
Original publication:
B. Kraus, F. Dawel, s. Hannig et al.
Phase-stabilized UV light at 267 nm through twofold second harmonic generation.
Optics Express 30, 44992-45007 (2022).
https://doi.org/10.1364/OE.471450
