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Broadband polarization-insensitive amplitude and phase modulators based on graphene-covered buried and ridge silicon waveguides
摘要： In this paper, four easy-to-fabricate graphene-based Si waveguide modulators are presented to overcome the strong polarization dependency of graphene-based modulators. The modulation features of two newly proposed structures, i.e. two graphene-based buried silicon waveguides in addition to two standard ridge silicon waveguides at the telecommunication wavelength of are studied. The results show that for certain widths of each waveguide (the height is constant), the amplitude and phase modulations clearly become polarization-insensitive. The amplitude modulation depths for both the TE and TM modes are equal for these optimized waveguides with the precision of . Moreover, in the proposed modulators, the maximum variations of the real parts of the effective mode indices (EMI) for both the TE and TM modes coincide with each other with an excellent precision ( . This precision value is much smaller than the standard criterion value for confirming a polarization-insensitive phase modulation. For proposed structures, the average modulation depth (MD) and maximum variation of the real parts of EMI are about and respectively. Thus, it means to clearly imply small footprints for both amplitude and phase modulations. Furthermore, the performances of all the structures are studied for all optical telecommunication wavelengths. Even without making any changes to the structures designed at at appropriate wavelength intervals, the structures exhibit polarization-insensitive behaviors.
关键词： Graphene,Polarization-insensitive,Optical modulator,Buried waveguide,Ridge waveguide
更新于2025-09-23 15:21:01
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Low-Loss Buried-Heterostructure Optical Waveguide Based on Impurity-Free-Vacancy-Diffusion Quantum Well Intermixing
摘要： A new method for fabricating a high-quality buried-heterostructure optical waveguide using quantum well intermixing (QWI) has been demonstrated. By patterning a SiO2 thin ?lm on top of a multiple quantum well (MQW) heterostructure, rapid thermal annealing (RTA) could induce laterally local QWI, resulting in a bandgap blueshift and a simultaneous decrease in the refractive index. Both lateral bandgap and index engineering could be attained along the MQW plane, which could be used for a buried-heterostructure optical waveguide. Two SiO2 strips with 3, 5 and 7 μm windows were fabricated for waveguide on a 1540 nm InGaAsP MQW sample. A 120 nm blueshift under the SiO2 area was observed, leading to the index contrast of 0.07. Far-?eld optical diffraction measurements were also performed to yield angles of 13.9°, 12.8° and 10.6°. A narrower window resulted in a narrower optical waveguide width and exhibited a larger diffraction angle, suggesting that QWI de?ned the buried optical waveguide. In addition, an electroabsorption modulator was also made by buried waveguide. A ?10 dB low optical insertion loss and a 15 dB high extinction ratio in a 500 μm long waveguide were obtained, indicating that a buried heterostructure could be used for photonic devices and integration applications.
关键词： Quantum well intermixing,buried waveguide,electroabsorption modulator (EAM).,low loss waveguide
更新于2025-09-19 17:13:59