Implementing an electronic sideband offset lock for isotope shift spectroscopy in radium

• Published in: Optics express 2023-12, Vol.31 (25), p.41326-41338
• Main Authors: Rabga, T, Bailey, K G, Bishof, M, Booth, D W, Dietrich, M R, Greene, J P, Mueller, P, O'Connor, T P, Singh, J T
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.500578

We demonstrate laser frequency stabilization with at least 6 GHz of offset tunability using an in-phase/quadrature (IQ) modulator to generate electronic sidebands (ESB) on a titanium sapphire laser at 714 nm and we apply this technique to perform isotope shift spectroscopy of Ra and Ra. By locking the laser to a single resonance of a high finesse optical cavity and adjusting the lock offset, we determine the frequency difference between the magneto-optical trap (MOT) transitions in the two isotopes to be 2630.0 ± 0.3 MHz, a factor of 29 more precise than the previously available data. Using the known value of the hyperfine splitting of the P level, we calculate the isotope shift for the S to P transition to be 2267.0 ± 2.2 MHz, a factor of 8 more precise than the best available value. Our technique could be applied to countless other atomic systems to provide unprecedented precision in isotope shift spectroscopy and other relative frequency comparisons.