Strongly Enhanced Four-Wave Mixing Signal from GaAs/AlAs Cavity with InAs Quantnm Dots Embedded in Strain-Relaxed Barriers

Strong ultrafast four-wave mixing signals at ${\sim}1.5$ μm were demonstrated in a GaAs/AlAs multilayer cavity containing self-assembled InAs quantum dots (QDs) embedded in strain-relaxed In0.35Ga0.65As barriers. Time-resolved optical measurements using 100 fs pulses with 100 kHz repetition rate were carried out in the various excitation powers at room temperature. Strongly enhanced four-wave-mixing signals were observed for a cavity with two InAs QDs layers inserted in a half-wavelength ($\lambda/2$) cavity layer compared with that of a GaAs $\lambda/2$ cavity that had no QDs, in the whole range of excitation power (0.3--2 mW). For a low excitation power below 0.6 mW, the four-wave-mixing signals were about two orders of magnitude larger than that of the GaAs $\lambda/2$ cavity owing to the large nonlinearity of the InAs QDs.