| Photonic crystal nanobeam cavity is a one-dimensional photonic crystal resonant cavity formed by introducing point defects into ideal photonic crystals.Because of its ultra-compact size,high Q-factor,low mode volume,easy waveguide integration and high compatibility with CMOS technology,it is considered as an ideal platform for realizing silicon photonic integrated devices.Nowadays,it has been widely used to realize various functional photonic integrated devices,such as light sources,optical modulator,optical switches,optical sensors and so on.With the development of modern information technology,photonic integrated devices are developing towards higher speed,lower power consumption and smaller size.In this paper,photonic crystal nanobeam cavity is taken as the research object,the realization andapplication in high-efficiency electro-optic modulation and high-sensitivity dual-parameter sensing are emphatically studied.The specific research work includes the following three parts:Firstly,this paper designs the ultra-low index-contrast electro-optic polymeric photonic crystal nanobeam cavities.In order to overcome the design difficulty caused by the ultra-low index-contrast between cavity and substrate material,based on the deterministic design method of nanobeam cavity,the photonic band structure,optical field distribution and transmission characteristics are studied in detail by using finite difference time domain method(FDTD)and finite element method(FEM),and the structural parameters are optimized,and finally a specific structural parameters of the subsequent electro-optic modulation research are determined.Secondly,based on the proposed nanobeam cavities,a novel high efficiency polymeric nanobeam cavities electro-optic modulator is proposed in this paper.Aiming at the structure model of ultra-low index-contrast nanobeam cavity,electro-optic overlap between the corresponding optical modes and in-plane DC electric fields is calculated.By optimizing electrode thickness and electrode gap,the relationship between metal absorption loss and electro-optic effect intensity is balanced,and the electro-optic response of the modulator is analyzed.The electro-optic modulation efficiency is up to 16 pm/V,and the device length is only 80?m,leading to a voltage-length product as low as 0.05 V·cm.Therefore,the ultra-compact and high-efficiency electro-optic modulator can provide a design idea for future electric-field sensing and tunable photonic devices.Thirdly,based on the design of the exsiting nanobeam cavity,a cascaded silicon-on-insulator photonic crystal nanobeam cavities for simultaneous detection of relative humidity and temperature is proposed.The proposed sensor consists of two independent PCNCs,one of which is covered by SU-8 cladding,and the other is coated with a water-absorbing PVA layer as the sensing cladding.We use a Y-junction power splitter to cascade the two nanobeam cavities.The RH sensitivities are 0 pm/%RH and-387 pm/%RH,and temperature sensitivities are-41.5 pm/K and 58 pm/K,respectively.In addition,considering the inaccuracy of detection results caused by external interference such as system errors and non-detected parameters in the actual detection process,?RH and ?T are defined to evaluate the anti-external interference ability.The ?RH and ?T of the proposed dual-parameter sensor are 0.006 and 0.024,respectively,indicating that the maximum RH and temperature detection errors caused by the deviation of resonant wavelength 1 pm are only 0.006%RH and 0.024 K.Therefore,the proposed sensor is expected to have an excellent anti-interference ability and good stability.Therefore,the proposed dual-parameter sensor in this section may provide a certain reference value for the future design of silicon-based optical sensor chip. |
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