Abstract
We present a systematical comparative research on the modulation performance and the optimization of the multi-slot waveguide modulator at the telecom wavelength of 1.55 μm. It is found that the existence of epsilon-near-zero indium tin oxide slots in modulators can enhance the optical confinement, thus yielding a high extinction ratio (ER) and low insertion loss. Among the designed four types of slot modulators, the single-slot modulator exhibits the widest modulation bandwidth of 78.75 GHz and lowest energy consumption of 1.15 pJ/bit, while the dual-slot one shows the moderate performance. For the more-slot designs, the tri-slot has the advantages of a maximum figure of merit of ~106, and the quadri-slot one has the highest ER of 1.38 dB/μm. By integrating the multi-slot modulator on the silicon waveguide, the quadri-slot modulator waveguide exhibits broad optical bandwidth of 83 nm from 1479 to 1560 nm and large modulation depth (~18.3 dB). The performance of four types of slot modulators can be further improved from different aspects by the optimization of their geometric parameters. The results of this work could be useful in the design and selection of high performance on-chip modulators for optical communications and ultrafast data processing.
Highlights
IntroductionElectro-optical modulators are the key drivers for optical communication and signal processing in short-reach interconnects in photonic integrated circuits on silicon [1], which demands higher modulation efficiency, broad optical bandwidth, small device footprint, low power consumption, and CMOS-compatibility [2], [3]
Electro-optical modulators are the key drivers for optical communication and signal processing in short-reach interconnects in photonic integrated circuits on silicon [1], which demands higher modulation efficiency, broad optical bandwidth, small device footprint, low power consumption, and CMOS-compatibility [2], [3].Significant development has been carried out in the conventional Si-based modulators with plasma dispersion effect where the free carrier concentration induces a change in the refractive index and absorption coefficient over a wide range of wavelengths [1]
We propose high-efficiency electro-optical epsilon-near-zero multi-slot waveguide modulator designs, which can be controlled by applying a voltage bias
Summary
Electro-optical modulators are the key drivers for optical communication and signal processing in short-reach interconnects in photonic integrated circuits on silicon [1], which demands higher modulation efficiency, broad optical bandwidth, small device footprint, low power consumption, and CMOS-compatibility [2], [3]. By adjusting the free carrier concentration, the real part of ITO’s permittivity can reach a close-tozero value at the telecommunication wavelength This effect is so-called epsilon-near-zero (ENZ) effect, which has exhibited many fantastic optical properties, such as enhancing light-material interaction, large nonlinear responses and strong coupling phenomena, etc [17]–[20]. The performance of slot electric-optical modulator can be further improved by sandwiching a thin ENZ film waveguide, yielding a small footprint, low insertion loss and ultrahigh modulation speed [16]. We propose high-efficiency electro-optical epsilon-near-zero multi-slot waveguide modulator designs, which can be controlled by applying a voltage bias. To explore the modulation performance of the modulator with different slot numbers, we perform a comparative study on the single-, dual-, tri-, and quadri-slot modulator of the multi-slot waveguide through systematic electrical and optical analyses.
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