Thermal effects on the excited state absorption and upconversion process of erbium ions in germanosilicate optical fiber

The effects of temperature on the excited state absorption of erbium ions a round 800 nm in germanosilicate optical fiber were studied at 300 and 77 K. Backward amplified spontaneous emission and upconversion fluorescence were monitored tuning the pump wavelength in the absorption band I-4(15/2) --> I-4(9/2). Optimal pump wavelength for backward amplified spontaneous emissi on was experimentally obtained, which was temperature dependent. Thermal po pulation in the Stark levels was found to affect the excited state absorpti on of the erbium ions resulting in shift of optimal pump wavelength and cha nge in conversion efficiency. (C) 1999 Elsevier Science B.V. All rights res erved.