Ultrasensitive and Broadband All‐Optically Controlled THz Modulator Based on MoTe₂/Si van der Waals Heterostructure

Abstract

Despite the impressive progresses in terahertz (THz) sources and detection, there is still a big challenge for high performance active optoelectronic THz devices such as THz modulators. All‐optically controlled THz modulators with large modulation depth (MD) and wide modulation bandwidth are of great importance for the THz technology. Herein, a MoTe2/Si van der Waals (vdWs) heterostructure is rationally designed as all‐optical THz modulator by taking advantage of their similar band alignment and easy integration with Si complementary metal‐oxide‐semiconductor (CMOS). The MoTe2/Si modulator presents an ultrasensitive THz modulation performance with a MD of 99.9% under a low illumination power of 300 mW at 1064 nm. This is a record MD for TMDCs‐based all‐optically controlled THz modulators to date. Moreover, the MoTe2/Si modulator exhibits broadband modulation performance with a wide frequency range from 0.3 to 2.0 THz. The high modulation performance under low illumination power is beneficial for practical application with low energy consumption and easy heat dissipation, which is advantageous to modulator chip. This work validates a facile protocol for fabricating high performance THz modulators and paves the way for their practical applications in THz technology.

Fabrication Technologies for the On‐Chip Integration of 2D Materials

“…[25,134,136,191,203] Integrated optical modulators have also been demonstrated, including electro-optic, [23,213,243] thermooptic, [232,283] and all-optical modulators. [22,284] By virtue of their low dispersion and large anisotropic light absorption, broadband polarization-selective devices based on graphene, [26] GO, [27] MoS 2 , [215] BP, [245] and MXenes [269] have been realized. 2D materials with superior NLO properties have been used for implementing high-performance all-optical signal processing devices based on four wave mixing (FWM), [193,205] self-phase modulation (SPM), [29,216] and second-harmonic generation.…”

Wafer-scale freestanding vanadium dioxide film

“…( B ) Transmittance of the CNT film, the f-VO 2 /CNT film, and the f-VO 2 /CNT film under electrical stimulation with a power density of 7.5 mW/mm 2 in the frequency range from 0.2 to 2 THz. ( C ) Comparison of the insertion loss and the modulation depth of the f-VO 2 /CNT THz modulator with other current-triggered or light-triggered THz modulators on substrates ( 26 , 42 – 51 ). ( D ) Transient response of the suspended f-VO 2 /CNT film under a square wave–modulated voltage with a frequency of 1 Hz.…”

Recent progress in terahertz modulation using photonic structures based on two‐dimensional materials

“…83 Another major strategy for enhancing the modulation performance of 2D-materials-based modulators is to increase carrier concentration by hybrid bulk semiconductors. 84 After years of effort, the modulation depth of 2D-based modulators has been greatly improved to nearly 100%. Nevertheless, the increase in the modulation depth is frequently associated with the higher insertion loss and slower speed of operation.…”

“…118,119 Recently, Qiao et al presented an ultrasensitive modulator using a MoTe 2 /Si hybrid structure, as shown in Figure 4(D). 84 The performance of the modulator was evaluated by THz time- D-H) Reproduced with permission from Qiao et al 84 Copyright 2020, Wiley-VCH domain spectroscopy (Figure 4(E)). With this device, a record modulation performance with a modulation depth of 99.9% was reached at the laser power of 300 mW (Figure 4(F)).…”