Ultra-efficient DC-gated all-optical graphene switch

High-Performance All-Optical Modulator Based on Graphene-hBN Heterostructures, 2022

Graphene has emerged as an ultrafast photonic material for on-chip all-optical modulation. However, its atomic thickness limits its interaction with guided optical modes, which results in a high switching energy per bit or low modulation efficiencies. Nonetheless, it is possible to enhance the interaction of guided light with graphene by nanophotonic means. Herein, we present a practical design of an all-optical modulator that is based on graphene and hexagonal boron nitride (hBN) heterostructures that are hybrid integrated into silicon slot waveguides. Using this device, a high extinction ratio (ER) of 7.3 dB, an ultralow insertion loss (IL) of <0.6 dB, and energy-efficient switching (<0.33 pJ/bit) are attainable for a 20 µm long modulator with double layer graphene. In addition, the device performs ultrafast switching with a recovery time of <600 fs, and could potentially be employed as a high-performance all-optical modulator with an ultra-high bandwidth in the hundreds of GHz. Moreover, the modulation efficiency of the device is further enhanced by stacking additional layers of graphene-hBN heterostructures, while theoretically maintaining an ultrafast response. The proposed device exhibits highly promising performance metrics, which are expected to serve the needs of next-generation photonic computing systems.

Photonic Network Communications, 2019

A compact electro-optical programmable logic device (PLD) which can provide any of 16 possible minterms of four Boolean variables on an optical signal is demonstrated in this paper. The presented structure is based on electro-optical graphenesilicon switches that consist of a Mach-Zehnder interferometer in which a few-layer graphene is embedded in silicon slot waveguide to construct phase shifters. A large effective index variation can be achieved by embedding few-layer graphene inside the slot waveguide which enables us to have a compact footprint. Our analysis shows that the presented PLD has a small footprint of 1.86 × 1.28 mm 2 . Any combinational logic circuit can be implemented by programming the proposed PLD. Here, the presented structure is programmed to work under three different modes including logical operations, two-bit adder, and two-bit comparator with the advantage of very fast switching among operation modes. Comparison with previous works shows that our design has a compact footprint, high extinction ratio, and low insertion loss with broadband spectrum for wideband telecommunication.

Low Insertion Loss Plasmon-Enhanced Graphene All-Optical Modulator, 2021

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 plasmonenhanced 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 alloptical modulator.

ACS Nano, 2014

Graphene is well-known as a two-dimensional sheet of carbon atoms arrayed in a honeycomb structure. It has some unique and fascinating properties, which are useful for realizing many optoelectronic devices and applications, including transistors, photodetectors, solar cells, and modulators. To enhance light–graphene interactions and take advantage of its properties, a promising approach is to combine a graphene sheet with optical waveguides, such as silicon nanophotonic wires considered in this paper. Here we report local and nonlocal optically induced transparency (OIT) effects in graphene–silicon hybrid nanophotonic integrated circuits. A low-power, continuous-wave laser is used as the pump light, and the power required for producing the OIT effect is as low as ∼0.1 mW. The corresponding power density is several orders lower than that needed for the previously reported saturated absorption effect in graphene, which implies a mechanism involving light absorption by the silicon and photocarrier transport through the silicon–graphene junction. The present OIT effect enables low power, all-optical, broadband control and sensing, modulation and switching locally and nonlocally.

Graphene, with its high optical nonlinearity and unique dispersionless nonlinear optical response over a broad wavelength range, has been studied extensively to implement optical devices such as fiber lasers, broadband modulators, polarizers, and optical switches. Conventionally synthesized graphene relying on high temperature and vacuum equipment suffers from deleterious transfer steps that degrade the graphene quality, thereby affecting the efficiency of nonlinear optical operation and lacking the customized patterning with minimized footprint as well as missing the facilitated fabrication process. Here, a laser-aided in situ synthesis of multilayered graphene directly onto the flat surface of a side-polished optical fiber in ambient condition is demonstrated for absolute investigation of an as-grown graphene crystal in the optical domain. The evanescent field of an amplified continuous wave laser, propagating through an optical fiber, provides activation energy for carbon atoms t...

ACS Nano, 2021

Graphene and related materials can lead to disruptive advances in next-generation photonics and optoelectronics. The challenge is to devise growth, transfer and fabrication protocols providing high (≥5000 cm2 V–1 s–1) mobility devices with reliable performance at the wafer scale. Here, we present a flow for the integration of graphene in photonics circuits. This relies on chemical vapor deposition (CVD) of single layer graphene (SLG) matrices comprising up to ∼12000 individual single crystals, grown to match the geometrical configuration of the devices in the photonic circuit. This is followed by a transfer approach which guarantees coverage over ∼80% of the device area, and integrity for up to 150 mm wafers, with room temperature mobility ∼5000 cm2 V–1 s–1. We use this process flow to demonstrate double SLG electro-absorption modulators with modulation efficiency ∼0.25, 0.45, 0.75, 1 dB V–1 for device lengths ∼30, 60, 90, 120 μm. The data rate is up to 20 Gbps. Encapsulation with s...

2021

With the growing demand for massive amounts of data processing transmission and storage it is becoming more challenging to optimize the trade off between high speed and energy consumption in current optoelectronic devices. Heterogeneous material integration into Silicon and Nitride photonics has demonstrated high speed potential but with millimeter to centimeter large footprints. The search for an electro optic modulator that combines high speed with energy efficiency and compactness to enable high component density on chip is yet ongoing. Here we demonstrate a 60 GHz fast (3dB roll off) micrometer compact and 4 fJ per bit efficient Graphene based modulator integrated on Silicon photonics platform. Two dual Graphene layers are capacitively biased into modulating the waveguide modes optical effective index via Pauli blocking mechanism. The electro optic response which is further enhanced by a vertical distributed Bragg reflector cavity thus reducing the drive voltage by about 40 time...

Journal of Semiconductors, 2018

Silicon photonics has attracted much attention because of the advantages of CMOS (complementary-metal-oxide-semiconductor) compatibility, ultra-high integrated density, etc. Great progress has been achieved in the past decades. However, it is still not easy to realize active silicon photonic devices and circuits by utilizing the material system of pure silicon due to the limitation of the intrinsic properties of silicon. Graphene has been regarded as a promising material for optoelectronics due to its unique properties and thus provides a potential option for realizing active photonic integrated devices on silicon. In this paper, we present a review on recent progress of some silicon-graphene photonic devices for photodetection, all-optical modulation, as well as thermal-tuning.

2015 European Conference on Optical Communication (ECOC), 2015

We will review state-of-the-art of hybrid graphene silicon photonics devices, discussing electro-absorption modulators, detectors and controllable saturable absorption.

Superlattices and Microstructures, 2019

In this paper, all-optical switches using a novel combination of graphene and insulator-metal plasmonic waveguides are proposed. For the proposed switches the optical Kerr effect is used to change the chemical potential of graphene-based plasmonic waveguides which are located in arms of a Mach-Zehnder interferometer. The phase mismatch induced due to the chemical potential variation triggers the switching mechanism. Three dimensional finite difference time domain (FDTD) method has been used for numerical investigation of the designed graphene switches. Silver is the metal used for the design of the Mach-Zehnder interferometer and GaAs is chosen as the Kerr material. The proposed all-optical switches can be used for highly integrated optical circuits and for all-optical signal processing.