1. A.S. Pine: J. Opt. Soc. Am. 64, 1683 (1974)
2. F.K. Tittel, D. Richter, A. Fried: In Solid-State Mid-Infrared Laser Sources, Topics in Appl. Phys. 89, I.T. Sorokina, K.L. Vodopyanov (eds.) (Spinger-Verlag, Berlin 2003), p. 445
3. R.G. Smith, J.E. Geusic, H.J. Levinstein, J.J. Rubin, S. Singh, L.G. van Uitert: Appl. Phys. Lett. 12, 308 (1968)
4. M. Ebrahimzadeh: In Solid-State Mid-Infrared Laser Sources, Topics in Appl. Phys. 89, I.T. Sorokina, K.L. Vodopyanov (eds.) (Spinger-Verlag, Berlin 2003) p. 179
5. J. Faist, F. Capasso, D.L. Sivco, C. Sirtori, A.L. Hutchinson, A.Y. Cho: Science 264, 553 (1994)