Excited-state absorption in Pr3+ : Y3 Al5 O12

Abstract

The optical-absorption transitions originating from the lowest 4f5d excited state of ${\mathrm{Pr}}^{3+}$ in ${\mathrm{Y}}_{3}$${\mathrm{Al}}_{5}$${\mathrm{O}}_{12}$ have been studied. The experimental arrangement uses a 7-ns 266-nm light pulse to populate the lowest 4f5d state, and a spatially overlapped, time-sequenced pulse from a frequency-tunable dye laser to induce transitions from that excited state. The excited-state-absorption (ESA) spectrum covering the 900--300-nm probe wavelength range is characterized by two broad peaks centered at 700 and 350 nm on a slowly rising background. The peak ESA cross section at 355 nm is (1\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}17}$ ${\mathrm{cm}}^{2}$. The position, shape, and strength of the spectrum suggest that the terminal states of the ESA transitions are the second 4f5d state of ${\mathrm{Pr}}^{3+}$ and the conduction band of the host lattice. The ESA measurements have been extended to transitions from the $^{3}$${\mathit{P}}_{0}$ and $^{1}$${\mathit{D}}_{2}$ excited states of the 4${\mathit{f}}^{2}$ configuration of ${\mathrm{Pr}}^{3+}$ as well. The ESA cross sections at a probe wavelength of 532 nm are (8\ifmmode\pm\else\textpm\fi{}1)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}19}$ ${\mathrm{cm}}^{2}$ and (5.7\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}19}$ ${\mathrm{cm}}^{2}$ for transitions from the $^{3}$${\mathit{P}}_{0}$ and $^{1}$${\mathit{D}}_{2}$ excited states, respectively. The terminal state of ESA transitions from these two levels is the lowest 4f5d state. The strong ESA completely inhibits the potential laser action based on emission from these states in this crystal.