Optically tuned terahertz modulator based on annealed multilayer MoS2

Abstract

Controlling the propagation properties of terahertz waves is very important in terahertz technologies applied in high-speed communication. Therefore a new-type optically tuned terahertz modulator based on multilayer-MoS2 and silicon is experimentally demonstrated. The terahertz transmission could be significantly modulated by changing the power of the pumping laser. With an annealing treatment as a p-doping method, MoS2 on silicon demonstrates a triple enhancement of terahertz modulation depth compared with the bare silicon. This MoS2-based device even exhibited much higher modulation efficiency than the graphene-based device. We also analyzed the mechanism of the modulation enhancement originated from annealed MoS2, and found that it is different from that of graphene-based device. The unique optical modulating properties of the device exhibit tremendous promise for applications in terahertz switch.

Optically pumped terahertz wave modulation in MoS2-Si heterostructure metasurface

“…17 The unique band structure of MoS 2 -Si heterostructure and the high mobility of MoS 2 make more carriers are generated on the Si surface. Shortly afterwards, a similar experiment result has also been confirmed by Cao et al, 18 and they have explained the enhancement mechanism in more details.…”

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

“…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.…”

“…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.…”

All-integrated terahertz modulators

“…A similar approach has also been reported with another bidimensional material, MoS 2 , on silicon in Ref. [20]. The effect of annealed MoS 2 on silicon yielded, at a pump power of 1 W from a 808 nm cw laser, an improved modulation depth as high as 64.9% at 0.9 THz, three times higher than bare silicon.…”

“…Accordingly, for sufficient high fluences and frequencies lower than the scattering rate γ, the semiconductor can exhibit a "metallic" behaviour and a negative dielectric constant. Interestingly, even complex 2D materials such as graphene or MoS 2 , whose bandgap depends on the number of layers [19,20], can be described by the Drude model at THz frequencies in the first approximation. Graphene is a bidimensional material which derives much of its remarkable properties from its zero bandgap and conical energy dispersion.…”