Abstract
The terahertz (THz) modulator, which will be applied in next-generation wireless communication, is a key device in a THz communication system. Current THz modulators based on traditional semiconductors and metamaterials have limited modulation depth or modulation range. Therefore, a THz modulator based on annealed tungsten disulfide (WS2, p-type) and high-resistivity silicon (n-type) is demonstrated. Pumped by a laser, the modulator presents a laser power-dependent modulation effect. Ranging from 0.25 to 2 THz, the modulation depth reaches 99% when the pumping laser is 2.59 W/cm2. The modulator works because the p-n heterojunction can separate and limit carriers to change the conductivity of the device, which results in a modulation of the THz wave. The wide band gap of WS2 can promote the separation and limitation of carriers to obtain a larger modulation depth, which provides a new direction for choosing new materials and new structures to fabricate a better THz modulator.
Highlights
With the devolvement of two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides (TMDs), some researchers have begun to combine 2D materials with metamaterials to fabricate THz modulators
The results of the experiment demonstrate that the THz modulator based on annealed WS2 and silicon has a rather large modulation depth when pumping by a Continuous wave (CW) source
THz modulators work by changing the conductivity of a device, which is primarily determined by the concentration of free carriers in the device
Summary
With the devolvement of two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides (TMDs), some researchers have begun to combine 2D materials with metamaterials to fabricate THz modulators. Weis et al first formed a THz modulator based on graphene pumping by a femtosecond laser pulse source[11]. WS2 has superior thermal and oxidative stability compared to MoS216,17 It only has a weak impurity band, which brings it much higher on/off ratios and much larger current in transistors and optoelectronic devices[18,19]. These excellent properties indicate that WS2 could be used as a new material to fabricate various electronic and optoelectronic devices. The results of the experiment demonstrate that the THz modulator based on annealed WS2 and silicon has a rather large modulation depth when pumping by a CW source. Based on our analytical model and experiment results, a clear direction for designing more effective THz modulators is noted
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