Optical amplification in Er 3+-doped fluoroindate glass at 840 nm and 1550 nm

Abstract

Er 3+-doped transparent fluoroindate glasses have been measured in a pump and probe setup in order to get optical amplification. High power laser pulses at 532 nm have been used as the pump source to strongly populate the 4S 3/2 ( 2H 11/2) levels of Er 3+ ions due to ground state absorption. Low signal beam cw laser radiation at 850 nm was used to stimulate the emission associated with the 4S 3/2 ( 2H 11/2) → 4I 13/2 electronic transition. The high power pump pulses allowed achieving population inversion between the Er 3+ levels of the transition 4S 3/2 ( 2H 11/2) → 4I 13/2. Under these conditions, positive optical gain around 1.33 cm −1 (5.7 dB/cm) has been measured in Er 3+-doped fluoroindate during the first 200 μs. Using a similar setup experiments of gain have been carried out for the 4I 13/2 → 4I 15/2 transition of the Er 3+ ions (at 1.5 μm). The obtained values are greater than 1.2 cm −1 (5.2 dB/cm) during the first 200 μs. Under these conditions and using the net cross-section simulation, the inversion population of the 4I 13/2 ↔ 4I 15/2 transitions could be estimated as 60% in order to obtain optical gain.