Evaluation of Laser Rate Parameters for Praseodymium Doped Yttrium-Aluminum

The radiative lifetimes, quantum efficiencies and transition rates for multiphonon decay of excited energy levels of Pr('+3) grown substitutionally in the host crystal YA O(,3) have been measured as a function of temperature so as to evaluate the feasibility of developing Pr('+3) as a four level laser operating in the visible. In addition the observed spectral intensities of radiative transitions and positions of some energy levels have been. compared to calculated values. The lifetime of the ('3)H(,6) level (13 (mu)s at 77(DEGREES)K) as a function of temperature was found using the infrared quantum counting technique. The lifetime of the ('3)P(,0) level (3 (mu)s at 77(DEGREES)K) and the lifetime of the ('3)P(,1) level (20.7 (mu)s at 77(DEGREES)K) as a function of temperature were also measured. The quantum efficiencies and transition rate as a function of. temperature were measured for the ('3)P(,1) ( --->) ('3)P(,0) non-radiative transition and the ('3)H(,6) (--->) ('3)H(,5) non-radiative transition. The transition rates were found to conform to earlier multiphonon theory and were found to depend only on the energy gap of the transition and the maximum Debye cutoff frequency of the YA O(,3). The process was determined to occur by lowest order. The. crystal field split levels for the ('3)H(,4), ('3)H(,5), ('3)H(,6), ('3)F(,2), ('3)F(,3) and ('3)F(,4) levels were. identified and found to be in reasonable agreement with values calculated elsewhere. Absorption of light for the ('3)P(,2), ('3)P(,1), ('3)P(,0) levels was found to be exceptionally strong for Pr('+3) in YA O(,3). Transition intensities for the ('3)P(,0) to. ('3)H(,4), ('3)H(,5), ('3)H(,6), ('3)F(,2), ('3)F(,3), ('3)F(,4) levels were measured and were found to be in poor agreement with the values calculated from he Judd -Ofelt theory using a set of crystal field parameters published elsewhere. The ('3)P(,0) to ('3)H(,6). transition was especially strong as was the ('3)P(,2), ('3)P(,1), ('3)P(,0) absorption and this combined with the ('3)H(,6), ('3)P(,0) and ('3)P(,1) lifetime suggest the possibility of at least a four level pulsed YA O(,3):Pr('+3) laser at (TURN) 6139 (ANGSTROM).