Richard Jarman - Spectroscopic Properties of CaF2:U4+ as a Saturable Absorber

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    Spectroscopic Properties of CaF2:U4+ as a   Saturable Absorber, J.B.   Gruber, D.K. Sardar, L.D. Merkle, B. Zandi, R.H. Jarman   and J.A. Hutchinson,   J. Appl. Phys., 90, 3965   (2001).


  The spectroscopic properties of crystals of CaF2:U4+ have been   examined in light of recent interest

  expressed for this material as a saturable absorber in the   passive Q switching of near infrared solid

  state lasers. The detailed crystal-field splitting of the energy   levels of U4+(5 f 2 ) is analyzed for the

  ion in different charge-compensated sites. Identification of the   site is based on laser excited

  site-selective spectroscopic studies reported earlier.   Experimental Stark levels are compared with

  calculated levels based on lattice-sum models that include charge   compensation in the lattice

  structure. The final set of atomic parameters for U4+ is in good   agreement with values reported for

  the ion in UF4. The predicted non-Kramers’ doublet as the   ground-state Stark level for U4+ in C3V

  sites is in agreement with the spectroscopic analysis and with   results reported earlier from electron

  spin-resonance studies of CaF2:U4+. Using pump–probe methods, we   have investigated excited

  state absorption (ESA) at 1.54 um. Consistent with the   interpretation of the absorption spectra, we

  find that the measured ESA is quite small in these crystals. In   turn, we use this conclusion to model

  CaF2:U4+ as a passive Q switch, with good results.

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