Fabrication of traveling wave type electro-optic quantum dot modulator

Abstract

Requirements for suitable communication systems with large capacity and high speed processing of information are rapidly on increase. Fiber-optic communication systems are presented for these requirements today. Modulation is one of the most important part in these system. Although many optical modulators already has been existed, for more high speed and performance we are interested in design of traveling-wave type electro-optic modulator which can be used for wide-band applications. Quantum dots(QDs) have long been expected to improve the performance of optical devices. Since their density of states due to the three-dimensional (3-D) carrier confinement behave as delta function, thus, QDs have the characteristics such as enhanced differential gain, suppressed thermal distribution of carriers, and a nearly zero alpha parameter at the peak gain. In this paper, we fabricated electro optic modulator using InAs/InGaAs columnar QD. The height of one QD is 4 nm and 10 periods of QDs are stacked including InGaAs capping layer. The peak wavelength of photoluminescence is 1260 nm at room temperature. The electrode of QD modulator is designed as Traveling-wave Mach-Zehnder type for high speed operation. And the microwave characteristics are simulated to design Traveling-wave QD modulator using Finite Difference-Time Domain method. Using simulation results, we fabricated Traveling-wave type quantum dot electro-optic modulator with varying the length of modulation region.