All-optical inverter operating with a 1.5 mu m laser in erbium-doped phosphate glass

The dependence of an all-optical inverter derived from the negative nonline ar absorption effect on both the modulation degree and frequency was invest igated in erbium-doped phosphate glass using a 1.5 mu m laser diode. With a decreasing degree of incident modulation, a reversed-phase waveform was ob tained in the transmitted laser at modulation degrees less than 86%. The re versed-phase transmitted waveforms were observed at modulation frequencies from 10 Hz to 250 MHz and at wavelengths from 1530.0 to 1545.0 nm. The wave length dependence of the negative nonlinear absorption effect agreed with t he transmitted spectra for the erbium-doped phosphate glass. The negative n onlinear absorption effect for 1.5 mu m can be explained by considering an enhanced absorption model for a four-level system of the Er3+ ion.