A Model of Lasing Action in a Quasi-Four-Level Thin Active Media Toroghi, S. ; Jafari, A. K. ; Golpayegani, A. H. Abstract Publication: IEEE Journal of Quantum Electronics Pub Date: June 2010 DOI: 10.1109/JQE.2010.2040368 Bibcode: 2010IJQE...46..871T