Graphene based plasmonic terahertz amplitude modulator operating above 100 MHz

Abstract

Articles you may be interested inFrequency and amplitude stabilized terahertz quantum cascade laser as local oscillator

All-integrated terahertz modulators

“…The advantages of an external modulation scheme lie in the possibility of modulating different frequencies separately, paving the way for independent frequency and phase modulation in quadrature with a single source. This approach yielded a lower modulation depth, ~20-30%, but a similar performance in modulation speed >110 MHz with a QCL emitting at 2 THz [68]. The design of any efficient optical modulator based on plasmonic/metamaterial requires a precise knowledge of the graphene electrical conductivity range, which can be tuned.…”

“…The miniaturization of the device was key in order to reduce all the capacitances and impedances in the circuit, which otherwise would limit the modulation speed. Interestingly, in this work, an indirect measurement of the frequency roll-off was proposed, which was developed in parallel by the group in Cambridge [67,68], working on the realization of graphene/plasmonic amplitude modulators operating external to the cryostat based on antenna and interdigitated bow-tie arrays. The advantages of an external modulation scheme lie in the possibility of modulating different frequencies separately, paving the way for independent frequency and phase modulation in quadrature with a single source.…”

“…In the architecture reported in Ref. [68], the graphene regions were reduced to arrays of a few μm 2 areas shunting the bow-tie arms, thus achieving the >110 MHz modulation speed, which was still limited by the parasitic capacitance introduced by the metallic contact pads. A schematic of the device is reported together with scanning electron microscope (SEM) images of the graphene/bow ties in Figure 7; the graphene regions are clearly distinguishable in the inset.…”

“…[70], the authors demonstrated more than 1-GHz modulation speed (even though significant degradation was observed already above 200 MHz) and 86% modulation depth. In this work, InAlN/AlN/GaN/AlN/GaN double-channel heterostructures supported a 2DEG channel [68] and as a detector [13]. Reprinted from Jessop et al [68], with the permission of AIP Publishing.…”

Active Frequency Modulation of Metamaterial/Graphene Optoelectronic Device Using Coupled Resonators

“…By fabricating metamaterial structures from basic sub-wavelength resonator antennas, the permittivity and permeability of the structure can be lithographically tuned to display optical features not normally observed in nature. In previous works [1,2] metamaterial resonant structures with strong optical reflection at THz frequencies have been reported which can be variably dampened by the electrostatic gating of monolayer graphene, resulting in amplitude modulator devices as fast as 100 MHz. Here, a similar electrical tuning mechanism has been used to demonstrate continuous frequency tuning of a metamaterial resonance whilst maintaining the Q factor of the resonance, with no detriment to the reconfiguration speed.…”