Applied Physics Letters
Optical signal inversion phenomenon for 1.53 μm laser in an erbium-doped lithium niobate
Yoshinobu Maeda, Hirotoshi Nagata, Taizou Nakashima, Junichiro Ichikawa, Kaoru Higuma
Abstract
Modulation characteristics of a negative nonlinear absorption effect were investigated in 3 wt % erbium-doped lithium niobate using a 1530 nm laser diode. With a decreasing incident modulation degree, a reversed-phase waveform was obtained in the transmitted laser at modulation degrees smaller than 85% for a sample length of 14 mm. The reversed-phase transmitted waveforms were observed at modulation frequencies from 1 kHz to 10 GHz. The negative nonlinear absorption effect for 1.5 μm can be explained by considering an enhanced absorption model for a four-level system of the Er3+ ion.