Examination regarding wavelength characteristics of the wide band optical amplifier operating in the 1μm region

摘要

An amplifier for laser light sources of the 1 μm region such as the Nd-YLF (1047,1053 urn) and the Nd-YAG (1064 nm) used in industrial and optical measuring fields is required. Though characteristics of the amplifier operating in the 1 μm region using Nd-doped fibers have been studied, wavelength characteristics of the gain and the noise figure regarding Yb-doped fibers which also have an amplification range in the 1 μm region have not been studied yet. By optimizing the YDF parameters such as cutoff wavelength and the Th concentration, we succeeded in developing a highly efficient Th-doped fiber amplifier (YDFA) that has a conversion efficiency of 66%. Furthermore, we developed a tunable fiber laser operating in the 1 μm region using YDFs as the amplification medium and used this laser as a signal light source for the YDFA. As a result of evaluating the wavelength characteristics of the gain and the noise figure of the YDFs, we found that the peak wavelength of the Yb gain exists at around 1030 nm. Small signal gain is over 42 dB, and noise figure is under 5.0dB. In addition, YDFAs are maintenance free, constructed entirely of fibers assuring high quality and stability. They can be used not only as an amplifier for lasers of the 1 μm region but also as an oscillator for pulse light sources.