Research On Electro-optical Modulation Devices On Silicon Substrates

In recent years,with the development of communication systems,the range of information exchange has exploded exponentially,and the demand for signal transmission capacity is increasing.With the advent of quantum computers,people no longer only pursue the exchange speed while taking into account the stability.In order to meet the demand for information processing improvement,people’s demand for chip integration has also gradually increased.Due to the continuous reduction of transistor size,Moore’s law has gradually become invalid.In the post-Moore era,integrated optical path is an important development direction.Traditional electronic chips are inevitably affected by quantum effects,and with the high degree of integration and ohmic heat dissipation,it is difficult for chips to break the limit of Moore’s Law.Compared with traditional electronic chips,optical chips have faster signal transmission speed and lower power consumption,and can become the primary solution of "overtaking in corners".For photonic chips,electro-optic modulators are essential if they want to achieve high-integration on-chip interconnection.Due to its excellent electro-optical characteristics,low cost and compatibility with CMOS technology,silicon material has become the preferred material for basic devices for on-chip interconnection.Electro-optical modulator devices usually include electro-optic modulator and optical switch.With the gradual improvement of on-chip integration,due to the limited chip size,the research of electro-optic modulator devices that take into account power consumption,polarization and mode is very important.At the same time,with the progress of basic scientific research,the excellent electro-optical properties of some low-dimensional materials have also been gradually discovered and applied in the research and development of silicon-based photonic chips.In this paper,starting with the device structure and materials,we have carried out research on the common polarization,power consumption and mode problems,and completed the following specific work:1.The research of silicon-based photonics is introduced,and the advantages and disadvantages of silicon-based photonic chips and electronic chips are compared.This paper summarizes the research significance of the interconnection of electro-optic modulators on silicon substrates,and summarizes the research progress of electro-optic modulators and electro-optic switches at home and abroad.Then the optical waveguide transmission characteristic equation and principle are deduced in detail,and the physical principle of electro-optical modulation is analyzed.At the same time,the numerical analysis and research methods of mode transmission are discussed,and the electro-optical effect of silicon materials and the working principle of auxiliary materials are introduced.2.On the basis of theoretical analysis,a polarization-insensitive graphene-assisted electro-optic modulator is designed to solve the polarization problem in on-chip electrooptic modulation.Orthogonal "inverted T" shaped metal slot waveguide structure provides polarization insensitivity.The double-layer graphene plate capacitor is introduced to modulate the electric absorption of graphene by changing its Fermi energy level.The proposed double-layer graphene structure can enhance the optical interaction and reduce the effective width of graphene.The two-dimensional material hexagonal boron nitride is used as the isolation layer to reduce power consumption and increase the working bandwidth,which is beneficial to increase the bandwidth and reduce power consumption.The simulation using finite element algorithm shows that the polarization insensitive modulation of TE mode and TE-TM complex mode supported by the proposed modulator has a modulation depth of 0.502 d B/μm and 0.511 d B/μm respectively.When the modulation length is at 20 μm,the 3 d B bandwidth is about 127 GHz,the power consumption can be limited to 72 f J/bit.3.Based on the SOI platform and COMS technology,a multimode asymmetric electro-optical switch is proposed.Through the design and optimization of the MMI and the size of the modulation arm,the switching effect of low loss and low crosstalk of the base mode/first mode switch is achieved.At the same time,a mode conversion switch is designed to meet the interconnection effect of the multimode switch.On this basis,an asymmetric switch structure is designed to achieve the pre-modulation effect by optimizing the length difference of the bent waveguide of the two modulation arms.In the pre-modulation state,its switching voltage can be reduced by 20%-25%compared with the traditional symmetrical optical switch,and the power consumption can be greatly saved in the integrated optical chip to improve the integration degree.At the same time,the proposed multimode asymmetric electro-optical switch has a lower insertion loss of about 1.3 d B and 1.4 d B in both the fundamental mode and the first mode,and its crosstalk performance also meets the switching requirements of about-29 d B and-30 d B.On this basis,use the switch unit to complete 4×4 Benes architecture switch array,the loss of the switch array built is less than 5 d B,the crosstalk is less than-30 d B under "All Bar",and the crosstalk is about-15 d B under "All Cross".