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Laser Transmitters: Coherent and Direct Detections
Published in Hamid Hemmati, Near-Earth Laser Communications, 2018
The electro-absorption modulator is a semiconductor device, wherein an applied electric field is used to change the absorption spectrum. Usually, carriers are not injected into the active region, but are generated due to light absorption. Waveguide type electro-absorption type modulators result in a higher extinction ratio relative to transmission type modulators.
Laser Transmitters: Coherent and Direct Detection
Published in Hamid Hemmati, Near-Earth Laser Communications, 2020
The electro-absorption modulator is a semiconductor device, wherein an applied electric field is used to change the absorption spectrum. Usually, carriers are not injected into the active region but are generated due to light absorption. Waveguide type electro-absorption type modulators result in a higher extinction ratio relative to transmission type modulators.
The enhanced phase modulation ability of optical modulator based on bi-layer graphene-silicon waveguide
Published in Journal of Modern Optics, 2018
Feng Zhou, Wei Du, Jiefang Zhang
According to different modulation mechanisms, modulators can be classified into phase, absorption and polarized modulators (3) which are usually made of silicon materials. However, since the electro-optic effect is too weak in silicon, conventional modulators are usually limited by narrow operation bandwidth, relatively low transmission speed and large footprint. Especially, the size of conventional silicon modulators could even reach the level of millimetre (4–7), which makes it impossible to be integrated on chip. To overcome those limitations, graphene-based modulators have attracted great interest due to its unprecedented properties such as enhanced interaction with light (8–10), high carrier mobility (11,12) and gate-controllable conductivity (13–15). For example, Liu has reported a 25 μm long electro-absorption modulator by placing a monolayer graphene on the top of silicon waveguide (8), and Jacek has reported a plasmonic electro-absorption modulator by embedding graphene in the centre of silicon waveguide with the length of only 1 μm (3). However, electro-absorption modulators are still limited by high energy consumption and low modulation depth.