We describe a systematic, rigorous procedure for the determination of the optical absorption saturation parameters for Cr<sup>4+</sup>:YAG and Cr<sup>4+</sup>:forsterite crystals at 1064 nm. A rate-equation approach was used to analyze the cw and pulsed transmission data of several crystals by accounting for the transverse as well as longitudinal variation of the beam intensity, saturation effects, and excited-state absorption. Use of an iterative procedure whereby the cw and pulsed data were simultaneously analyzed led to a considerable reduction in the error for the determination of cross sections. The average value of the absorption cross section sigmaa and the normalized excited-state absorption cross section fp=sigma<sub>esa</sub>/sigma<sub>a</sub> were determined to be 6.13×10<sup>−19</sup> cm<sup>2</sup> and 0.45, respectively, for Cr<sup>4+</sup>:forsterite and 19.6×10<sup>−19</sup> cm<sup>2</sup> and 0.06, respectively, for Cr<sup>4+</sup>:YAG. Detailed comparison was also made with previous saturation measurements in the literature. Our results further show that lumped models based on the thin-length approximation should be used with caution in the determination of cross sections, especially when the pump beam is tightly focused inside the absorber.
© 2006 Optical Society of America
Lasers and Laser Optics
Original Manuscript: March 4, 2005
Revised Manuscript: July 31, 2005
Manuscript Accepted: September 7, 2005
Alphan Sennaroglu, Umit Demirbas, Sarper Ozharar, and Fatih Yaman, "Accurate determination of saturation parameters for Cr4+-doped solid-state saturable absorbers," J. Opt. Soc. Am. B 23, 241-249 (2006)