Metal-clad-suspended self-biasing graphene modulator with tunable figure of merit
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RESEARCH ARTICLE
Metal-clad-suspended self-biasing graphene modulator with tunable figure of merit Jiamin Liu1
•
Zia Ullah Khan1 • Siamak Sarjoghian1
Received: 8 November 2019 / Accepted: 2 July 2020 Ó The Author(s) 2020
Abstract In this letter, a research on the metal-clad-suspended self-biasing graphene modulator is conducted theoretically. The results reveal a higher light–graphene interaction for the more compact modulator. In addition, when the light–graphene interaction is enhanced, the light–metal interaction is also higher, which causes larger insertion loss and makes the figure of merit (FOM) lower. The length of pphase shift is reduced to 6.35 lm for the Mach–Zehnder modulator, which is the smallest size achieved up to date. The modulator’s FOM can be tuned by changing the air gap (d) between the moveable metal plates and the suspended structure. In the case when this air gap increases, the configuration represents closer fundamental limits design. Moreover, the cut-off mode is discussed, and it has potential to be used in the tunable filter application. This tunable configuration of modulator is believed to have potential that can pave the way to design tunable light–matter interaction device and has evaluated for the near fundamental limits design. Keywords Graphene modulators Figure of merit Suspended Filter
Introduction Graphene modulators show greater application prospect than traditional silicon modulators since it was firstly demonstrated and reported in 2011 [1]. This is because the fundamental limits [2] of graphene modulator are much & Jiamin Liu [email protected] 1
School of Electronic Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK
further than that of the modulator made by traditional materials such as silicon. Graphene has much broader and deeper tunable absorption [3] and ultrahigh mobility [4, 5] in the wide band wavelength from visible light to THz band for the interested electro-modulation and absorption. Till now, all the figure of merits (FOMs) of modulator made by graphene, such as modulation depth, modulation speed, operation bandwidth, footprint, and modulation efficiency are much better and far beyond than that of traditional modulators. In this field, in order to realize near fundamental limits designing, different modulator structures are put forward [6–10]. The main purpose is to enhance the light–graphene interaction. Researchers have found that the symmetrical structure [6, 7] can make the mode with lower insertion loss and higher modulation depth, so the light–graphene interaction is enhanced further. The figure of merit (FOM) of graphene modulator is defined as the ratio of modulation depth to insertion loss. And the FOM can be an index of how the design is approaching the fundamental limits (it’s a relation between insertion loss and modulation depth, as described in Ref. [2]) of graphene modulator. In our recently work [11–13], we have reported the suspended graphene modulators which are already much near the fundament
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