GaAs/AlAs Multilayer Cavity with Er-Doped InAs Quantum Dots Embedded in Strain-Relaxed InGaAs Barriers for Ultrafast All-Optical Switches

Abstract

Er-doped InAs quantum dots (QDs) embedded in strain-relaxed InGaAs barriers, which exhibit an extremely short carrier decay time of 3 ps due to the nonradiative process, are superior materials for ultrafast all-optical switches using a GaAs/AlAs multilayer cavity. The intensity of the nonlinear signal due to the absorption saturation in the 20-layer stack of the Er-doped QDs was increased by increasing the In composition in the strain-relaxed InGaAs barriers while keeping the extremely short decay time. The QD cavity structure, which consisted of GaAs/AlAs distributed Bragg reflector (DBR) multilayers and a half-wavelength cavity layer containing two layers of the Er-doped QDs was grown by molecular beam epitaxy. The transmission change signal was clearly observed in the time-resolved measurements at the cavity mode wavelength of 1.55 µm. The response time of 4 ps was observed for the Er-doped QD cavity, which was much shorter than that (12 ps) for the undoped QD cavity.

GaAs/AlAs multilayer cavity with Er-doped InAs quantum dots embedded in extremely thin strain-relaxed InGaAs barriers for ultrafast all-optical switches

“…Time-resolved measurement for the thick strain-relaxed barrier sample was performed using the same structure but top DBR multilayer grown at high T s of 570ºC instead [6], because the sample with the top DBR multilayer grown at low T s of 480ºC had the poor quality of DBR multilayer, as mentioned before. Figure 4 shows the temporal profiles of normalized transmission change measured for the Er-doped QD cavities with thin (T s = 480ºC) and thick (T s = 570ºC) strain-relaxed InGaAs barriers.…”

“…Furthermore, the decay time can be further shortened (~ 3 ps) by Er-doping during the molecular beam epitaxy (MBE) of the InAs QDs with strain-relaxed InGaAs barriers [5]. Recently, we have grown the GaAs/AlAs multilayer cavity with the Er-doped InAs QDs embedded in the strain-relaxed InGaAs barriers for the ultrafast all optical switches [6]. However, a growth temperature of a top DBR multilayer was needed to increase to maintain the good structural quality of the sample.…”

Photonic switching devices based on semiconductor nano-structures

“…This allows the vertical-cavity switch to exhibit higher differential reflectivity and in the meantime to keep the fJ level operation power. Besides the low power consumption, several approaches have been proposed to accelerate the absorption dynamics of QD switches down to a few picoseconds using physical mechanisms such as the carrier tunneling to an additional QW [83], or the introduction of non-radiative recombination using various impurity dopants [84,85].…”

GaAs/AlAs Multilayer Cavity with Er-Doped InAs Quantum Dots Embedded in Thin Strain-Relaxed In0.45Ga0.55As Barriers for Ultrafast All-Optical Switches

“…20) Recently, we have grown a GaA/AlAs multilayer cavity with Er-doped InAs QDs embedded in a high In concentration strain-relaxed In 0:45 Ga 0:55 As barrier for ultrafast alloptical switches. 21) In this structure with a high refractive index =2 cavity layer, the optical field is enhanced at the sides of the cavity layer. Thus, two separated Er-doped InAs QDs layers were embedded in the sides of the cavity layer to enhance the optical nonlinearity.…”