Molecular beam epitaxy of AlAsSb/AlAs/InGaAs coupled double quantum wells with extremely thin AlAs center barrier

Cross Phase Modulation Efficiency Enhancement in In0.8Ga0.2As/Al0.5Ga0.5As/AlAs0.56Sb0.44Coupled Double Quantum Wells by Tailoring Interband Transition Wavelength

“…6 and showed a greater increase in the coupling strength as compared to that the structures studied in ref. 8. Optical absorption measurements revealed that the IBT-EW of the new CDQWs was successfully red-shifted to over 1450 nm.…”

“…In order to red-shift the IBT-EW of the CDQWs, the following lattice matched and mismatched CDQWs were studied: (1) CDQWs consisting of In 0:53 Ga 0:42 As wells and In 0:52 Al 0:48 As center barriers 6) and (2) In 0:8 Ga 0:2 As wells and extremely thin AlAs center barriers. 8) The reason for examining both structures was to study the effect of an increase in the coupling strength between two wells. This aim leads lowering the 1st quantized energy level.…”

“…Due to the strong coupling between the two wells, the width of the In 0:8 Ga 0:2 As well was designed to be wider than the wells used in previous studies. 6,8) The large width was required to adjust the wavelength of the optical absorption due to the ISBT between the 1st and 4th subbands to around 1550 nm. An increase in the coupling strength caused a decrease in the 1st quantized energy level and an increase in the 4th quantized energy level.…”

“…This feature provides a significant advantage in comparison to CDQWs presented in previous studies. 6,8) In series (1), the CDQWs were stacked 60 times to obtain sufficient optical absorption strength due to IBT and ISBT. Series (2) consisted of 65 periods of CDQWs that was followed by 1 m Al 0:9 Ga 0:1 As 0:56 Sb 0: 44 10) for the upper cladding layer.…”

“…This observation indicates that the crystal quality of the CDQWs was good. 8) Optical absorption due to the IBT and ISBT was measured by a Fourier transform infrared (FTIR) spectrometer. For the investigation of the IBT, light was radiated on samples in a direction normal to the surface.…”