Pulse stretching utilizing two-photon-induced light absorption

Author(s): A. Hordvik
Sponsor(s): IEEE Lasers and Electro-Optics Society
Publisher: IEEE - Institute of Electrical and Electronics Engineers, Inc.
Publication Date: 1 April 1970
Volume: 6
Page(s): 199 - 203
ISSN (Paper): 0018-9197
ISSN (Online): 1558-1713
DOI: 10.1109/JQE.1970.1076438



The effect of inserting an element exhibiting induced absorption into aQ-switched laser cavity is investigated theoretically and experimentally. The rate equations are solved assuming two types of nonlinear loss, one being proportional to the square of the laser intensity and the other being proportional to the product of laser intensity and density of excited electrons in the nonlinear absorber. Experiments are performed with a rotating-prism ruby laser with a CdS crystal in its cavity. It is established that two-photon absorption takes place, and as predicted by the theory that the output intensity and output energy both decrease and pulse length increases as compared with the normalQ-switched case. In addition, the output pulse has an oscillatory behavior, and it is suggested that this is caused by loss due to the excited electrons, which are found to have a lifetime of approximately 24 ns.