Investigation of Semiconductor Quantum Dots for Waveguide Electroabsorption Modulator

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.

InGaAs self-assembly quantum dot for high-speed 1300nm electroabsorption modulator

“…On comparing the work of Refs. [4,[8][9][10], our work shows clear QCSE and thus optical modulation with relatively short waveguide length (300 mm), suggesting that the strong exciton effect of QD covers inhomogenous broadening effect in dot size distribution. Therefore, further growth techniques to increase the dot density and uniformity of dot size, are still aspired to enhance the performance of extinction ratio.…”

“…Different results of the linear redshift have been mentioned in [9,10], which attribute the nonquadratic relation to the strong charge screening through power dependent excitation and also the small dot height. In this work, low incident power below 1 mW was used in the experiment.…”

“…Based on the self-assembled InGaAs QD formation, the development of 3-dimensional quantum structure has been successfully and widely used in gain-related optoelectronic devices such as laser and optical amplifiers [5][6][7]. By such QD development, several groups have also worked on the QD application based on QCSE, such as electroabsorption properties, high-power excitation, high-speed carrier dynamics, and modulator performance [4,[8][9][10]. From the view, point of device application, EAM using well-developed quantum well (QW) material have been demonstrated with high-speed high-efficient performance by broadband microwave design and engineering [11,12].…”

Characteristics of 1.3 μm InAs/InGaAs/GaAs quantum dot electroabsorption modulator

“…Reverse bias of up to 10 V, controlled by a dc voltage supply, was applied through the electrical probe and the experimental setup was described elsewhere. 16 Recognizing that the absorption edge occurs at ϳ1325 nm, 16 the transmitted power versus reverse bias curves ͑i.e., transfer curves͒ were extracted from 1300 to 1350 nm, in steps of 1 nm. This gives a total of 51 curves and the wavelength that gives the largest extinction ratio ͑ϳ10 dB͒ was determined, i.e., ϳ1328 nm in our work.…”

“…1, where a value of 1.0 is defined as the transmission across the InAs/InGaAs/GaAs QD-EAM when the reverse bias is zero. In addition, the full width at half maximum ͑FWHM͒ of the fundamental absorption peak was extracted 16 and presented in the inset of Fig. 1.…”