Computer modelling of thorium doping in LiCaAlF6 and LiSrAlF6: application to the development of solid state optical frequency devices
This paper describes computer modelling of thorium doping in crystalline LiCaAlF6 and LiSrAlF6. The study has been motivated by the interest in using these materials as hosts for 229Th nuclei, which are being investigated for use as frequency standards. The dopant sites and form of charge compensation are obtained; this information is essential for the further development and optimization of these devices.
Optical spectroscopy of an atomic nucleus: Progress toward direct observation of the 229Th isomer transition
Abstract The nucleus of the thorium-229 isotope possesses a first excited nuclear state ( 229m Th) at an exceptionally low energy of 7.8±0.5 eV above the nuclear ground state ( 229g Th), as determined by earlier indirect measurements. This is the only nuclear excited state known that is within the range of optical spectroscopy. This paper reports progress toward detecting the 229m Th state directly by luminescence spectroscopy in the vacuum ultraviolet spectral region. The estimated natural linewidth of the 229g Th↔ 229m Th isomer transition of 2 π ×0.1 to 2 π ×10 mHz is expected to broaden to ∼10 kHz for 229 Th 4+ doped into a suitable crystal. The factors governing the choice of crystal system and the substantial challenges in acquiring a sufficiently large quantity of 229 Th are discussed. We show that the 229g Th↔ 229m Th transition energy can be identified to within 0.1 nm by luminescence excitation and luminescence spectroscopy using the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. This would open the door for subsequent laser-based measurements of the isomer transition and future applications of 229 Th in nuclear clocks. We also show that 233 U-doped materials should produce an intrinsic, continuous, and sufficiently high rate of 229m Th→ 229g Th luminescence and could be a useful aid in the initial direct search of the isomer transition.
Blue-lines pumped Kerr-lens mode-locked Cr:LiSGaF laser
Abstract We report a blue-lines pumped femtosecond Kerr-lens mode-locked Cr:LiSGaF laser based on a tight-focusing geometry. With a combination of 488, 476 and 458 nm lines as a pump source, 58 fs pulses centered at 845 nm were generated. The average output power is 30 mW, and time–band product is 0.331, assuming a sec h2 pulse shape. Neither acousto-modulator nor physical aperture or slit were used in this cavity.