Nanogroove control of intersubband absorption in AlGaAs/GaAs step quantum wells

In this work, the intersubband absorption between the ground and the top subbands is numerically studied in a three-level AlGaAs/GaAs step quantum well (SQW) structure with an InGaAs nanogroove layer. The calculations show that the intersubband optical absorptions can be tuned easily by varying the parameters of the nanogroove layer, such as the position, thickness and indium concentration. Of these, the indium concentration of the InGaAs nanogroove layer is found to be the best parameter because the tunable range is easy to control and the corresponding peak values are kept with relatively small difference. Compared with conventional SQWs, a SQW with a nanogroove layer has the advantage of improving absorption strength. This study is focused on the intersubband absorptions in the energy range of 0.112 similar to 0.133 eV, therefore the corresponding results are useful to the optimization of optically pumped terahertz lasers with CO2 lasers as the pumping sources.