SPECTRAL AND TEMPORAL BEHAVIOR OF AN ERBIUM DOPED FIBER LASER

Abstract The dynamics of an erbium doped fiber laser are analysed under continuous and modulated pumping. It is found that the bondaries between different modes depend only on the pump parameter and the lifetime of the photon in the cavity. Spectral and temporal behaviors are analysed. Fiber lasers are potential laser sources for optical coherent communication (1) We believe that these lasers could also be used in spectroscopy with their wavelength region in the mid infra-red (2)(3) or in the visible range by up conversion (4). They have low threshold and can be pumped with diode lasers. Unfortunately fiber lasers exhibit high nonlinearity leading to spontaneous relaxation. Our aim is to use a fiber laser for intracavity laser absorption spectroscopy (ICLAS) (5). In this technique, the spectro-temporal dynamics play an important role. We present here the spectral and temporal behavior of such a laser. Fig.1 Schematic diagram of the experiment. Figure 1 shows the experimental arrangement of the erbium laser pumped by a krypton ionized laser. Throughout this work, the pump wavelength was fixed at 647 nm which corresponds to the transition 4 ~ g / 2 t 4~15/2. The pump beam passes through an acousto-optic modulator (AOM). In cw pumping, the AOM is used as a variable attenuator. The intensity of the first order beam can then be changed without any angular deviation, which usually happens when the krypton laser power is monitored electrically. Such procedur