Graphene based All-Optical Spatial Terahertz Modulator

Wen, Qiye; Tian, Wei; Mao, Qi; Chen, Zhi; Liu, Weiwei; Yang, Qinghui; Sanderson, Matthew R.; Zhang, Huaiwu

doi:10.1038/srep07409

Cited by 180 publications

(67 citation statements)

References 29 publications

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“…Modulation techniques attempted hitherto include the following: metasurface structures based on split ring resonance effects, [1][2][3][4] liquid crystal, 5,6 and conductive thin film transmission attenuation. [7][8][9][10][11][12][13][14][15][16][17] However, these devices can have limited bandwidth, slow switching speeds, and remain challenging to scale up to large areas. Conductive thin film attenuation where the conductive layer is generated by either photo-exciting free carriers on the surface of semiconductor wafers or by electrically gated 2D materials represents a promising avenue for the realization of such a device.…”

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confidence: 99%

“…7 However, the ion-gel gated graphene devices, like the liquid crystal devices, 5,6 have slow operational speeds. Optical methods could achieve broadband MD up to 99% with much faster speeds [12][13][14][15][16][17] but very high optical pump intensity is required. Even with the assistance of p-n junction structures based on 2D [12][13][14] or organic materials 15,16 to increase the carrier density and mobility, the required pumping power is still very high (as shown in Table I), and this is likely to reduce the lifetime of the material.…”

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confidence: 99%

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Exploiting total internal reflection geometry for efficient optical modulation of terahertz light

Parrott

Ung

et al. 2016

APL Photonics

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Efficient methods to modulate terahertz (THz) light are essential for realizing rapid THz imaging and communication applications. Here we report a novel THz modulator which utilizes the evanescent wave in a total internal reflection setup coupled with a conductive interface to enhance the attenuation efficiency of THz light. This approach makes it possible to achieve close to 100% modulation with a small interface conductivity of 12 mS. The frequency dependence of this technique is linked to the optical properties of the materials: a material with close to frequency independent conductivity that is also controllable will result in an achromatic modulation response, and the device performance can be optimized further by tuning the internal reflection angle. In this work, we focus on applying the technique in the terahertz frequency range. Using an LED array with a pump intensity of 475 mW/cm2 to produce carriers in a silicon wafer, we have achieved a modulation depth of up to 99.9% in a broad frequency range of 0.1 THz–0.8 THz. The required pumping power for the generation of the required free carriers is low because the sheet conductivity needed is far less than required for traditional transmission techniques. Consequently, the device can be modulated by an LED making it a very practical, low cost, and scalable solution for THz modulation.

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confidence: 99%

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confidence: 99%

Exploiting total internal reflection geometry for efficient optical modulation of terahertz light

Parrott

Ung

et al. 2016

APL Photonics

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“…10 Since then, Wen et al proposed optically active modulators based on the graphene on the germanium substrate. 11 In 2015, an active graphene-Si hybrid diode for THz waves was proposed by Li et THz waves effectively. 12 These studies demonstrate that 2D materials have a huge potential in THz modulations.…”

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confidence: 99%

Optically pumped terahertz wave modulation in MoS2-Si heterostructure metasurface

et al. 2016

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An optically pumped terahertz (THz) modulator based on a MoS2-Si heterostructure metasurface are fabricated and investigated in this paper. The THz wave modulation in MoS2 metasurface has been demonstrated by THz time domain spectroscopy experiment and numerical simulation, which can reach over 90% under the continuous wave laser pumping of 4W/cm2 power density. Importantly, the catalysis of photocarrier generation in MoS2-Si heterostructure has been proved by the comparsion between the modulation depth of metasurface with and without MoS2 nanosheet under the same pumping power, and we found that the strcuture of metasurface and polariztion direction can also influence the photocarrier density in MoS2 metasurface. This novel THz modulator based on 2D material has a high effective modulation on THz waves under a low pumping power, which has a bright potential in THz applications.

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“…By using 0.8 W pump power from a 1550 nm cw laser, the authors in Ref. [45] managed to achieve a modulation depth of 94% for graphene on germanium, significantly higher than the 64% reported for germanium alone. By implementing narrow-bandwidth, frequency-selective InSb gratings instead, a modulation depth of 46.7% for TM polarization at 1.5 THz has been reported in Ref.…”

Section: All-optical Devicesmentioning

confidence: 99%

“…This effect was attributed to the trapping of photo-generated holes in MoS 2 , which led to an increase of electron concentrations and conductivity in silicon. Germanium has also been proposed as a possible host material for the graphene transfer [45] in all-optical THz modulators reporting the remarkable performance of a maximum ~94% modulation depth and ~200 kHz modulation speed over a broadband 0.25-1 THz region. In contrast to the case of silicon, the increase in the modulation depth achieved by transferring graphene on top of germanium was attributed to nonlinear effects in the optical conductivity of graphene.…”

Section: All-optical Devicesmentioning

confidence: 99%

All-integrated terahertz modulators

et al. 2017

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Terahertz (0.1-10 THz corresponding to vacuum wavelengths between 30 μm and 3 mm) research has experienced impressive progress in the last few decades. The importance of this frequency range stems from unique applications in several fields, including spectroscopy, communications, and imaging. THz emitters have experienced great development recently with the advent of the quantum cascade laser, the improvement in the frequency range covered by electronic-based sources, and the increased performance and versatility of time domain spectroscopic systems based on full-spectrum lasers. However, the lack of suitable active optoelectronic devices has hindered the ability of THz technologies to fulfill their potential. The high demand for fast, efficient integrated optical components, such as amplitude, frequency, and polarization modulators, is driving one of the most challenging research areas in photonics. This is partly due to the inherent difficulties in using conventional integrated modulation techniques. This article aims to provide an overview of the different approaches and techniques recently employed in order to overcome this bottleneck.

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Graphene based All-Optical Spatial Terahertz Modulator

Cited by 180 publications

References 29 publications

Exploiting total internal reflection geometry for efficient optical modulation of terahertz light

Exploiting total internal reflection geometry for efficient optical modulation of terahertz light

Optically pumped terahertz wave modulation in MoS2-Si heterostructure metasurface

All-integrated terahertz modulators

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