Investigation of Semiconductor Quantum Dots for Waveguide Electroabsorption Modulator

• Published in: Nanoscale research letters Vol. 3; no. 12; pp. 486 - 490
• Main Authors: Ngo, C. Y, Yoon, S. F, Loke, W. K, Cao, Q, Lim, D. R, Wong, Vincent, Sim, Y. K, Chua, S. J
• Format: Journal Article
• Language: English
• Published: United States New York : Springer-Verlag 2008; BioMed Central Ltd; SpringerOpen
• Subjects: Electroabsorption modulator; InAs quantum dots; Optical transmission; Photocurrent; Ridge waveguide structure
• ISSN: 1931-7573; 1556-276X; 1556-276X
• DOI: 10.1186/1556-276X-3-486

In this work, we investigated the use of 10-layer InAs quantum dot (QD) as active region of an electroabsorption modulator (EAM). The QD-EAM is a p-i-n ridge waveguide structure with intrinsic layer thickness of 0.4 μm, width of 10 μm, and length of 1.0 mm. Photocurrent measurement reveals a Stark shift of ~5 meV (~7 nm) at reverse bias of 3 V (75 kV/cm) and broadening of the resonance peak due to field ionization of electrons and holes was observed for E-field larger than 25 kV/cm. Investigation at wavelength range of 1,300-1320 nm reveals that the largest absorption change occurs at 1317 nm. Optical transmission measurement at this wavelength shows insertion loss of ~8 dB, and extinction ratio of ~5 dB at reverse bias of 5 V. Consequently, methods to improve the performance of the QD-EAM are proposed. We believe that QDs are promising for EAM and the performance of QD-EAM will improve with increasing research efforts.