Abstract
We propose a U-shaped pn junction in a silicon-on-insulator microdisk resonator to effectively double the junction-mode overlap in the state-of-the-art, vertical pn junction microdisk electro-optical (EO) modulators. The U-shaped pn junction promotes the maximum overlap between the junction depletion zone and the whispering gallery optical mode in the microdisk. By fully depleting the p region of the npn-sequenced U-junction, the capacitance is reduced below 3 fF, which significantly improves the speed and power performance. In this work, we implement the high-efficiency, depleted U-junction design to maximize the operating bandwidth of EO modulators, EO logic elements, EO 2 × 2 switches for wavelength-division cross-connects, 2 × 2 reconfigurable optical add-drop multiplexers, optical-to-electrical-to-optical (OEO) repeaters-with-gain, OEO wavelength converters, and 2 × 2 optical-optical logic gates. These devices all operate in the 7.6-to-50 GHz bandwidth range with ultralow energy consumption between 0.4 and 9.8 fJ/bit. By using CMOS-compatible materials and fabrication-feasible design dimensions, our proposed high-performance devices offer a promising potential in next-generation, high-volume electro-optical communications and computing circuits.
Highlights
This theoretical, simulation-based study proposes a high-efficiency bus-coupled electro-optical microdisk modulator design for ultrahigh-speed and low-power communications and computing applications on the silicon-photonics integrated-chip platform
This 2 × 2 device can be utilized in important communications and computing applications, such as electro-optical logic (EOL) gates [11,13,14,15], wavelengthdivision multiplexed (WDM) NxNxMλ spatial routing switches [16,17], and reconfigurable optical add-drop multiplexers (ROADMs) [18,19]
We demonstrate the implementation of the proposed modulator in multifunctional optical-to-electrical-to-optical (OEO) devices for optical signal restoration-with-gain, wavelength conversion, and optical–optical logic (OOL)
Summary
This theoretical, simulation-based study proposes a high-efficiency bus-coupled electro-optical microdisk modulator design for ultrahigh-speed and low-power communications and computing applications on the silicon-photonics integrated-chip platform. We demonstrate the implementation of the proposed modulator in multifunctional optical-to-electrical-to-optical (OEO) devices for optical signal restoration-with-gain, wavelength conversion, and optical–optical logic (OOL). Given the high modulation efficiency of the depletion-mode U-junction modulator, the EOM, EOL, NxNxMλ cross-connect, ROADM, OEO repeater/converter, and OOL all operate, as optimized in this paper, between 7.6 and 50 GHz in bandwidth, with suitably low levels of energy consumption, between 0.4 and 9.8 fJ/bit, while maintaining more than 10 dB ER in an ultracompact, 2-μm-radius disk. The high bandwidth targeted in this paper for the device structures illustrated in Figs. 1 and 2 serves three purposes: it provides an extremely high (i) “information bandwidth” for analog or digital modulation of light in an optical interconnect or communications link, (ii) bit/sec rate for digital modulation—a rate that is about twice the optical bandwidth, and (iii) switching rate, or rate of “reconfiguration” for 2 × 2 switching elements
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