|| Self-assembly semiconductor quantum dot (QD) has been widely used as optoelectronic applications due to its delta-function-like density of state, insensitive to photon scattering, the capability of mass production, greatly enhancing quantum confined and exciton effect.Therefore, device applications, such as, electroabsorption modulator(EAM) and semiconductor optical amplifier (SOA) can have benefits over the conventional types through such active region. In this work, a monolithic integration of cascaded EAM and SOA based on QD material is proposed and demonstrated. Through high-speed cascaded electrode design to eliminate electrical parasitics, high-speed of QD carrier escaping processing and thus electroabsorption modulation can thus be observed.|
In the device characterization, electro luminescence (EL) is first used to examine the optical transition of QD, showing 1200-1220 nm for ground state. Using the EL spectrum measurement, the red shift of 20 nm in photocurrent peaks from 0V to 10V is observed. Also, the peaks exhibit a quadratic relation against with bias, confirming QCSE effect of QD. In the optical transmission measurement, 1260 nm light excites on a 580 μm long device, obtaining 1.6dB extinction(QD’s inhomogeneous) by voltage swing of 10V. By the high-speed electronic cascaded circuit(CI) such that the bandwidth response bias is very sensitive and the use of multi-stage to increase E-O response, leading to 3dB bandwidth of higher than 30GHz.