Abstract
Nowadays there is much interest in compact fiber lasers and amplifiers operating in the visible spectral region because of their numerous applications, including optical data storage, medical diagnostics and laser material processing. Recently, as a candidate for laser and amplifiers at the 0.54 μm band, Tb3+-doped fiber has been investigated by the author. The 5D4→7F5 transition of Tb3+ acts as a four-level laser system by 5D4 level (20600 cm1) pumping at a wavelength of 488 mn and a signal gain of 5.5 dB has been confirmed in a Tb3+-doped fluoride fiber[l], Furthennore, it is known that co-doping of Yb3+ in Tb3+-doped materials leads to visible upconversion emission by the Yb3+-Tb3+ cooperative energy transfer process[2]. In this process two excited Yb3+ (sensitizer) ions simultaneously transfer their energy to a Tb3+ (activator), so that Tb3+ can be excited to the 5D4 level. Because Yb3+ ions have the strong absorption cross section in the region of 0.98 μm, we can take advantage of high-performance 0.98 pm laser diode to excite Tb3+ ions. The probability of cooperative energy transfer was speculated at most 1% by T. Kushida[3], But the study of the energy transfer efficiency from Yb3+ to Tb3+ has been superficial, so far. In this study, we investigate the possibilities of Yb3+-Tb3+ cooperative energy transfer process which enable the 0.98 μm pmnping for Tb3+ ions using various host glasses. The energy transfer efficiency as high as 60±11 % was observed for the first time in a borosilicate glass and it was found out that Tb3+-Yb3+-codoped borosilicate glass was a promising candidate for the 0.54 μm band laser medium pumped at 0.98 μm.
© 2007 IEEE
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