Large aspect ratio (ratio of diameter to length) Ti- sapphire crystals, used in amplifiers of high-power lasers , suffer from amplified spontaneous emission and parasitic generation inside the crystal [2,3] that causes decay of population inversion and limits achievable gain. Parasitics can be suppressed by cladding the edge surface of a crystal [2,3], but only below certain transverse gain. And any way, it is difficult to use this method for high average power and/or cryogenically cooled laser systems  because cladding generally reduces thermal conductivity. In some cases, however, it is possible to avoid parasitics and reduce ASE by changing method of pumping and amplification in Ti-sapphire amplifiers. In the multi-pass amplifiers the high gain causing ASE and parasitics could be reduced by partial-extraction of the stored energy by the amplified pulse during pumping process.
© 2003 Optical Society of AmericaPDF Article