Photonic Crystal Waveguide And Microcavity Controling Light Properties And Sensing Mechanism Research

Since the physics concept of photonic crystals is proposed in the last late eighties, with the development of micro-nanofabrication technology, various photonic crystal devices in theoretical, experimental and applied aspect have made great progress. Among these devices, due to the special advantages of typical high-sensitivity, high resolution, fast response, anti-interference, reusable and easily to be miniaturized and integrated, photonic crystal as a new platform used for micro-nano sensors research are particularly interesting and have obtained great attentions all over the world. In particular, photonic crystals are considered as "optical semiconductor". Therefore, photonic crystals are also the first choice in the future photonic integrations and integrated optics applications, where the highly integrated, low-power, high-sensitivity micro-nano sensor networks is one of the important content to achieve everywhere perception in the future research.In this doctoral dissertation, to study photonic crystal waveguide and microcavity controlling light properties and sensing mechanisms, two dimensional (2D) silicon photonic crystals are used as study subjects. By using plane wave expansion (PWE) and finite-difference time-domain method (FDTD) methods, we calculate the photonic band diagram, transmission properties, and optical field distribution profile of photonic crystal waveguides and microcavities to study the controlling light properties. Then, based on the study of photonic crystal waveguide and microcavity controlling light properties, we investigate the sensing mechanisms, properties and applications of photonic crystal sensors. The contributions of this doctoral dissertation mainly can be summarized as follows.1) The theoretical research of the photonic crystal waveguide and microcavity controling light properties. To study photonic crystal microcavity controlling light properties, a novel ultra fast electro-optic slow light modulator based on2D coupled photonic crystal resonator arrays (CPCRAs) is demonstrated. The proposed structure consists of a triangular lattice with hexagonal Si dielectric rods filled polystyrene substrate. The simulation results demonstrated that in the vicinity of band edge, an ultra low group velocity of10-3c can be achieved (c is the group velocity of light in vacuum). The group delay approaches200ps. When modulating voltage is OV,0.3V and0.5V, the group delay is about3.1ps,4.3ps and7.6ps. The wavelength shift modulation sensitivity is about9.34nm/V. Then, in order to study photonic crystal waveguide controlling light properties, a novel compact and sensitive electro-optical sensor based on slotted photonic crystal waveguide (S-PhCW) is demonstrated. By applying three-dimensional finite difference time domain (3D-FDTD), the simulation results demonstrate that the sensitivity of W1-PhCW based electro-optical sensor and S-PhCW based electro-optical sensor is2.7nm/v and87.0nm/v, respectively. Compared with the W1-PhCW based electro-optical sensor, the sensitivity of the S-PhCW based electro-optical sensor is enhanced more than30times. The Q factor of the W1-PhCW based electro-optical sensor is66.73, while the Q factor of S-PhCW based electro-optical sensor is441.40, an enhancement of6.6times. As a result, it shows that the proposed electro-optical sensor based on S-PhCW did have improved the performance greatly compared to the reference one based on W1-PhCW.2) The theoretical research of sensing mechanism and sensing properties of photonic crystal based sensor and integrated sensor-array. Based on the study of photonic crystal waveguide and microcavity controlling light properties, in order to further investigate the controlling light properties of the integrated structure between photonic crystal waveguide and microcavity, a novel micro electro-optic sensor structure and its sensing technique based on photonic crystal waveguide and microcavity integrated structure are demonstrated. The properties of the sensor are analyzed and calculated using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method. The simulation results display that the resonant wavelength of the mode localized in the microcavity shifts its spectral drop position following a linear behavior when a driving voltage ranging between0.0V and3.2V is applied, and the sensitivity of31.90nm/V is observed. In order to further enhance sensors array integration density and multiplexed sensing properties, a novel Nanoscale Photonic Crystal Sensor Arrays (NPhCSAs) on monolithic substrates is proposed. The architecture consists of arrays of lattice-shifted resonant cavities side-coupled to a single PhC waveguide. Each resonant cavity has slightly different cavity spacing and is shown to independently shift its resonant peak in response to the changes in refractive index. The extinction ratio of well-defined single drop exceeds20dB. With three-dimensional finite-difference time-domain technique, the simulation results demonstrate that the refractive index sensitivity of～100nm/RIU is achieved and a refractive index detection limit is approximately of8.65X10"5. Then, to further reduce the crosstalk between adjacent sensor units and improve the performance of integrated sensors array, a flexible design of building nanoscale photonic crystal integrated sensors array with low crosstalk is theoretically investigated. Simulation results demonstrate that the proposed sensors array is desirable to perform monolithically integrated sensing and multiplexed detection. Particularly, the design method here makes it possible to effectively enhance sensors array integration density and simultaneously restrain crosstalk between each other adjacent sensors.3) The fabrication and measurement of nano-integrated photonic crystal sensor with high sensing properties. In order to further enhance the FOM of photonic crystal sensor, a novel nano-slotted parallel multibeam cavity possesses unexplored high S and high Q. The simulation results demonstrated that the refractive index sensitivity S～S10nm/RIU (refractive index unit) and Q>107in liquid at telecom wavelength range when absorption is neglected can be achieved. To the best of our knowledge, this is the first geometry that features both high S and Q factors. In addition, we experimentally demonstrate a label-free sensor based on nanoslotted parallel quadrabeam photonic crystal cavity (NPQC). The NPQC possesses both high sensitivity and high Q-factor. We achieved sensitivity of S=451nm/RIU and Q-factor>7000in water at telecom wavelength range, featuring a sensor FOM>2000, an order of magnitude improvement over previous photonic crystal sensors. Finally, we measured the streptavidin-biotin binding affinity and detected10ag/mL concentrated streptavidin in the phosphate buffered saline solution.4) Besides the contents mentioned above, we also investigate silicon photonic crystal used for micro displacement senor and torsion-free pressure sensor applications. A novel micro displacement sensor formed by a fixed and a mobile hole-array based slot photonic crystal (slot-PhC) components is demonstrated. By using FDTD, the simulation results display that with a proper operating frequency, a quasi-linear measurement of micro-displacement is achieved with sensitivity of1.Oa-1(a is the lattice constant). In addition, a novel nanoscale torsion-free photonic crystal pressure sensor is demonstrated. The simulated pressure sensitivity as high as0.50nm/nN is observed. The minimum detectable pressure variation is estimated to be as small as0.68nN.