Nano Photonic Sensors Based On Leaky Modes Resonance Effect

Leaky modes resonance (LMR) effect occurs when the illuminating wave is phasematched to a leaky waveguide mode by an appropriate periodic grating layer. For such adevice, a nearly100%diffraction efficiency peak in the reflection or transmissionspectrum occurs at a particular angle and wavelength, when the incidentelectromagnetic wave couples to the leaky mode. LMR filters are new class of filtersdue to the character. Compared with a conventional optical thin-film filter, the LMRfilters have fewer layers and looser thickness tolerances. Based on the thin film theory(TFT), effective media theory (EMT), rigorous coupled-wave analysis (RCWA), theresonance action and diffraction characteristics of LMR effect; narrowband, widebandand edge filter characteristics of LMR filter were analyzed in this thesis. And thefabrication process of LMR filter, the design and manufacture of sandwich widebandfilter were discussed. Effects of the structural errors on LMR filters were analyzed, onecompensation method was propounded. The sensitivity of LMR filter biosensors wereanalyzed in this thesis.The LMR filter was analyzed and designed. The spectral width and sidebandreflection was analyzed for narrowband filter. One wideband filter can be achieved byusing one sandwich grating structure, the broad reflection band results was fromcoexistence and interaction of the two leaky modes. Each peak in the reflection curvescorresponds to a modal resonance. The numerical results showed one rectangular andflattop spectral was obtained under normal incidence for TE polarization with flatteningbandwidth7nm. One edge filer was designed by asymmetric grating profiles structure,the numerical results showed the average transmission at1550nm wavelength exceeds99%was achieved, the reflection at1310nm97%is achieved.The samples of narrow LMR filters were made through electron beam deposition,laser holographic and ion beam etching processes. One double-layer LMR filterconsisting of a grating layer, a waveguide layer, and a substrate was constructed. Thesurface-relief grating layer was ZrO2, same to the waveguide layer. The samples weretested and analyzed. One set of process was initially established in LMR filtersmanufacture. The narrow LMR filters were obtained at first with17nm line width,72%zero order diffraction efficiency, less than7%sideband reflection. One sandwichwideband filter was obtained through two grating bonding face to face; both the sides of bonding were surface-relief grating. The new sandwich LMR filter broadened thansingle LMR filters in reflectance spectrum, results of the test showed broadenedbandwidth about30nm.The effects of the construction parameter errors on a typical LMR filter wereanalyzed. The simulated results indicated that the fabrication errors of the waveguidelayer, grating layer, period, and groove depth had a linear or partially linear relationshipwith the peak wavelength shift and the change of line width. The grating period errorand waveguide layer thickness error had a key influence on the peak wavelength ofLMR filter. The period needs to be controlled accurately in fabrication. The gratinglayer thickness error and the groove depth error had a little influence on spectrumproperties of LMR filter. A step-by-step compensation method was illustrated toeliminate fabrication errors during the fabrication process. The early fabrication errorsmay be compensated in the succeeding fabrication steps; only the error of the last stepcannot be eliminated.The sensitivity of the LMR biosensors to the sample refractive index and thicknesswas analyzed using rigorous coupled wave analysis method. The dependency was firstlybuilt between the sensitivity of LMR biosensors and resonance peak wavelength.Numerical Results indicated that for a certain resonance peak wavelength, thesensitivity of the LMR biosensors did not change when the sample refractive indexvaried, but drastically decreased and achieved constant sensitivity with increasedsample thickness. When the resonance peak wavelength increased, the sensitivityimproved in relation to both sample refractive index and sample thickness. Furthermore,the capability of sample thickness improved with longer resonance peak wavelength.These results are helpful in obtaining optimal LMR biosensors.In this thesis, a study of Nano photonic sensors based on leaky modes resonanceeffect, some existing problems and their solutions were discussed for LMR filters, sometheoretical basis was provided for the design of LMR filters, and the design was verifiedthrough experiments. The results of this study can promote the development of LMRfilters, it can make LMR filters technique utilized and industrialized.