Low Insertion Loss Plasmon-Enhanced Graphene All-Optical Modulator

Abstract

Graphene has emerged as an ultrafast optoelectronic material for all-optical modulators. However, because of its atomic thickness, it absorbs a limited amount of light. For that reason, graphene-based all-optical modulators suffer from either low modulation efficiencies or high switching energies. Through plasmonic means, these modulators can overcome the aforementioned challenges, yet the insertion loss (IL) of plasmon-enhanced modulators can be a major drawback. Herein, we propose a plasmon-enhanced graphene all-optical modulator that can be integrated into the silicon-on-insulator platform. The device performance is quantified by investigating its switching energy, extinction ratio (ER), IL, and operation speed. Theoretically, it achieves ultrafast (<120 fs) and energy-efficient (<0.6 pJ) switching. In addition, it can operate with an ultra-high bandwidth beyond 100 GHz. Simulation results reveal that a high ER of 3.5 dB can be realized for a 12 μm long modulator, yielding a modulation efficiency of ∼0.28 dB/μm. Moreover, it is characterized by a 6.2 dB IL, which is the lowest IL reported for a plasmon-enhanced graphene all-optical modulator.

High-Performance All-Optical Modulator Based on Graphene-hBN Heterostructures

“…The absorption of graphene can be tuned based on the principle of Pauli-blocking [40]- [42], which occurs when photoexited electrons fill the conduction band states of graphene following a sufficiently intense pump excitation, thereby blocking the interband transition of other electrons [14]. Figure 4a illustrates the interband absorption of a pump photon with an energy ω pump > 2|µ|, where µ is the chemical potential of graphene.…”

“…Similarly, a probe photon with an energy ω probe ≤ ω pump is also transmitted because ω probe < 2|µ |. By utilizing this phenomenon, all-optical modulation is realized: the probe signal is transmitted when the pump signal is HIGH, or absorbed when the pump signal is LOW [14]. Hence, the modulation mechanism is based on the saturable absorption of graphene [40]- [42].…”

“…Other plasmon-enhanced all-optical graphene modulators have been reported in refs. [13], [14]. Nonetheless, incorporating plasmonic metals into these devices introduces an excessive insertion loss (IL), mainly due to the inherent ohmic losses that are induced by these metals [15].…”

Plasmonic Photovoltaic Double-Graphene Detector Integrated Into TiN Slot Waveguides

“…The work function values of graphene and TiN are taken as 4.6 eV [40], [41] and 4.3 eV [42], respectively. Graphene is unintentionally doped when placed on a substrate, yielding a chemical potential (μ) in the range of 0.1-0.2 eV [4], [43], [44]. Within this range, Φ B < 0 as shown in Fig.…”

“…It exhibits unique optoelectronic properties that are of interest from a technological perspective such as ultra-high mobility and broadband absorption [2]. In addition, its 2D nature enables its facile with silicon photonics (SiPh) and microelectronics using complementary metal oxide semiconductor (CMOS) processes [3], [4]. In recent years, onchip graphene photodetectors have been demonstrated with a bandwidth exceeding 110 GHz [5]- [7].…”