This paper presents a method for the separation of excited-state absorption transitions from different initial levels by phase-sensitive detection by use of the double-modulation technique. This technique is also applicable for the distinction of spectrally overlapping transitions, and in connection with Judd-Ofelt calculations it allows the excited-state absorption cross sections to be determined. With this method, the 5I_7 --> (5S_2, 5F_4), 5I_6 --> (5G_6, 5F_1), 5I_6 --> 5F_2, and 5I_6 --> 5F_3 transitions in the spectral range between 720 and 860 nm in Ho3+-doped YLiF4 were measured and their cross sections determined. The method can be used for any similar system.
© 2005 Optical Society of America
Stefan Kück, Eugen Osiac, and Irena Sokólska, "Phase-sensitive detection of excited-state absorption transitions in Yb3+-codoped, Ho3+-doped YLiF4," J. Opt. Soc. Am. B 22, 323-327 (2005)