Broadband absorption bleaching in chirped InGaAs quantum dot semiconductor optical amplifier operating at 1211–1285 nm

•We see potential of chirped InGaAs QD structure in broadband semiconductor optical amplifier application.•We show spectral correspondence of absorption bleaching and time resolved absorption recovery for chirped QD structure.•Complexity of chirped structure causes impact on suppressing absorption bleaching from QD surrounding area.

We report on photoinduced absorption bleaching of InAs/InGaAs chirped quantum dot semiconductor optical amplifier (QD SOA) waveguide devices investigated by the traditional femtosecond pump–probe technique applied for a waveguide configuration. To gain broader spectra for the device a chirped QD structure including three groups of quantum dots each dedicated to a ground state transition at wavelength 1285, 1243 and 1211 nm was designed. Photoinduced transmission spectra consisting of ground state transition for the groups of QD’s involved showed coincidence with the electroluminescence spectra and even more exceeded to longer wavelength. From photoinduced transmission kinetics absorption recovery in the range of picoseconds was considered. For comparison a device with typical high photoinduced absorption demonstrating large suppression of absorption bleaching was shown and interpreted.