| Photonic crystals(PhCs)based label-free sensing technology has great potential as a highly sensitive,high-throughput,and compact that has vast applications in biomedical research,healthcare,pharmaceuticals,and environmental security.The PhC refers to a heterogeneous structure composed of a periodic arrangement of low-loss dielectric materials with contrasting refractive index(RI),which constrains the light propagation in certain ways such that the optical properties of the PhC are particularly sensitive to changes in RI.Since the interaction of target analytes with light causes the change of local RI,which in turn makes PhC suitable for investigating sensing properties.In this doctoral dissertation,PhC slabs are used as study subjects,by using plane wave expansion(PWE)method,we calculate photonic band gap(PBG)of PhCs with different dimensions and defects.Meanwhile,by using finite-difference time-domain(FDTD)method,localized properties,optical field distribution profile and transmission properties are also investigated for different PhC microcavities.In addition,the sensing properties of different PhC structures are analyzed.According to above research strategy,firstly,various microcavities based on one-dimensional(1D)and two-dimensional(2D)PhC slabs are analyzed and investigated.And sensing properties of each microcavity are explored and measured,we obtain a variety of high-performace PhC microcavities sensors.Secondly,in order to realize sensor array,different bend structures based on 2D-PhC slabs are analyzed and studied,high-performance PhC splitters are obtained.Eventually,based on the parallel integration of PhC splitter and PhC microcavities,high-performance PhC sensor array is realized.The contributions of this doctoral dissertation mainly can be summarized as follows:(1)The high-quality-factor and high-sensitivity PhC microcavities sensors and remote sensing based on microring resonance laser were proposed.Firstly,the H2 microcavity was designed based on 2D-PhC slab.High-extection-ratio and high-tranmission resonant peak were obtained through shifting the air holes around the microcavity.The number and position of air holes around H2 cavity were functionalized to study sensing properties,such that a high sensitivity was obtained.Secondly,an extra air hole was added to the center of the optimized H2 microcavity,and the high quality factor(Q)was obtained though change the radius of hole.The geometry of PhC microcavity will be defonnated through applied pressure,the pressure sensor was also realized.Combined with simulation results,the ultra-low detectable limit(DL)will be obtained.Additionally,a higher Q of mcrocavity will be reached by shifting the neighboring holes around the L3 microcavity.Finally,in order to obtain simultaneously high sensitivity(S)and high Q,two design methods of nanoslotted nanobeam cavities were proposed based on 1D-PhC slab.The first method(trial-and-error)was appled to repeatly simulate and analyze PBG,field distribution and transmission such that a high Q was obtained.In order to improve the coupled efficiency of light and microcavity,the ridge waveguides were applied to couple with the input and output of nanoslotted nanobeam cavities.A high S was obtained by changing the refractive index around the cavities.The second method(deterministic)was only applied to analyze and calculate the PBG and quadratic tapered air holes were designed to obtain high Q of 107.The S of 415 nm/RIU was achieved by putting the sensor immersed into liquids with different RI.Furthermore,ultra-compact sensor size of only 11.2?m×0.8?m was obtained.In addition,the micro-ring laser consisted of a fused-silica micro-ring with a channel profile as a cladding layer and a cured R6G-doped SU-8 or TZ-001 gain material deposited on it as a core layer.The characterization of lasing spectra of both micro-ring lasers within the different time intervals verified their good photostability.The microring laser-based refractive index sensing was performed based on a free-space optics measurement setup.By repeatedly alternated water and lemon juice,the S and detection limit(DL)of R6G-doped polymer SU-8 laser-based refractive index sensor were estimated.(2)The large-bandwidth and high-transmission PhC bend waveguides and splitters were demonstrated.Firstly,the 60° bend waveguide based on PhC slab was optimized by changing the size and displacement of air holes around the bend region.The high transmission was realized in the broadband region.Based on the above-optimized 60°bend waveguide,the 1×4 broadband high transmission splitter was obtained by the parallel integration of four bend waveguides.In order to further reduce the complexity of splitter design,only adding triangular air holes into the bend region such that the 1×3 broadband splitter was realized.(3)The low-crosstalk,high-extinction-ratio and high-sensitivity parallel multiplexing sensor were proposed based on the integration of PhC splitter and PhC microcavities.Firstly,based on the integration of the optimized 1×4 beam-splitter and the optimized L3 microcavities with four independently different peaks,parallel-integrated sensor array was proposed.Each microcavity was filled with liquids involving different refractive index,thus,each PhC sensor's S that S1=60.5nm/RIU,2=59.6nm/RIU,S3=62.5nm/RIU,and S4=51.1nm/RIU were calculated,respectively.In addition,the DL was estimated to be as small as 1×10-4 by further simulations and calculations.Secondly,in order to further increase single sensor's S in the sensor array,the optimized 1×3 beam-splitter,three bandpass filters composed by three W1 waveguides,and three coupled nanobeam cavities with three independent peaks were parallel-integrated on the monolithic chip.Through changing the RI around each sensor unit,the sensitivities of 492nm/RIU,244nm/RIU and 552nm/RIU were obtained,respectively. |
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