Abstract
Abstract We design and demonstrate an asymmetric Ge/SiGe coupled quantum well (CQW) waveguide modulator for both intensity and phase modulation with a low bias voltage in silicon photonic integration. The asymmetric CQWs consisting of two quantum wells with different widths are employed as the active region to enhance the electro-optical characteristics of the device by controlling the coupling of the wave functions. The fabricated device can realize 5 dB extinction ratio at 1446 nm and 1.4 × 10−3 electrorefractive index variation at 1530 nm with the associated modulation efficiency V π L π of 0.055 V cm under 1 V reverse bias. The 3 dB bandwidth for high frequency response is 27 GHz under 1 V bias and the energy consumption per bit is less than 100 fJ/bit. The proposed device offers a pathway towards a low voltage, low energy consumption, high speed and compact modulator for silicon photonic integrated devices, as well as opens possibilities for achieving advanced modulation format in a more compact and simple frame.
Highlights
With the rapid development of optical communication and interconnection, the photonic integrated circuits (PICs)For Ge-based modulators, the Ge/SiGe multiple quantum well electroabsorption modulators based on quantum confinement Stark effect (QCSE) have been demonstrated to implement small footprint and low energy dissipation [15, 16], but the applied bias voltage is still a little high to obtain a high extinction ratio
A preliminary demonstration of the electrorefractive index variation in Ge/SiGe multiple quantum wells [18] has been reported with an effective refractive index variation of 1.3 × 10−3 but the associated bias voltage is as high as 8 V, which limits its practical applications
The electro-optical characteristics can be further improved by coupled quantum wells structures and the CQWs structure has been widely investigated in III–V group material for various applications [19,20,21]
Summary
With the rapid development of optical communication and interconnection, the photonic integrated circuits (PICs). A preliminary demonstration of the electrorefractive index variation in Ge/SiGe multiple quantum wells [18] has been reported with an effective refractive index variation of 1.3 × 10−3 but the associated bias voltage is as high as 8 V, which limits its practical applications. The electro-optical characteristics can be further improved by coupled quantum wells structures and the CQWs structure has been widely investigated in III–V group material for various applications [19,20,21]. It has been theoretically and experimentally demonstrated that the symmetric Ge/SiGe coupled quantum wells can strongly enhance the electrorefractive index variation. The proposed device paves the way to realizing a compact, low voltage, low energy consumption and high speed modulator in silicon photonic integration for both intensity and phase modulation
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