Abstract

Conventional band of the cladding-pumped ytterbium-doped fiber (YDF) lasers in which high efficiency can be easily achieved is about 1060–1130 nm [1]. Efficient high-power lasers at shorter wavelengths are of great importance in some applications, e.g., in optical pumping of upconversion thulium-doped fiber amplifiers in which optimum pump wavelength of about 1020 nm was found [2]. The shorter is the lasing wavelength the higher has to be the average population inversion along the fiber. The effect of strong amplified spontaneous emission (ASE) in YDF significantly lowers the inversion. Therefore, bandstop filter for blocking strong ASE in YDF would increase the inversion. Recently, long-period fiber gratings (LPFGs) were used to suppress ASE of the Nd-doped fiber Fabry-Perot laser at ~1060 nm and therefore allowing lasing at emission peak ~1088 nm [3].

© 2009 IEEE