A novel InGaAs/AlAs/AlAsSb quantum well structures for ultrafast and low-power all-optical switches using intersubband transitions

This paper reports the effects of the AlAs interface layer on the quantum wells (QW) and intersubband transitions (ISBT) properties. High quality QWs were obtained by having 4-6 multilayers of AlAs interface layer and increasing In composition in InGaAs to accommodate strain. The X-ray diffraction spectra of typical InGaAs/AlAs/AlAsSb QWs clearly demonstrate the high quality. Using coupled double quantum wells with 2.8 nm In/sub 0.82/Ga/sub 0.18/As, ultra low saturation intensity (Is) of 34 fJ//spl mu/m/sup 2/ was obtained from the multipass waveguide geometry sample. These results open the door for realization of ultra-first all-optical ISBT switch.