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Open Access Nano Express

Investigation of Semiconductor Quantum Dots for Waveguide Electroabsorption Modulator

CY Ngo1*, SF Yoon1, WK Loke1, Q Cao1, DR Lim1, Vincent Wong2, YK Sim2 and SJ Chua3

Author Affiliations

1 School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore

2 Temasek Laboratories @ NTU, Nanyang Technological University, 50 Nanyang Drive, Singapore, 639798, Singapore

3 Institute of Materials Research and Engineering, 3 Research Link, Singapore, 117602, Singapore

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Nanoscale Research Letters 2008, 3:486-490  doi:10.1007/s11671-008-9184-7

Published: 21 October 2008

Abstract

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.

Keywords:
InAs quantum dots; Electroabsorption modulator; Ridge waveguide structure; Photocurrent; Optical transmission