The Design And Research Of Visible Wave Combiner Based On Photonic Crystal

Laser display technology is the fourth generation display technology after black and white display, color display and digital high-definition display technology. To use three-color laser light source, a multiplexer is needed which can make different wavelengths through the multiplexer output from the same port. Photonic crystals in the visible light wave combiner has the advantages of compact structure and high integrated, which is conducive to the laser light of miniaturization and low cost.What’s more, it also has alluring application prospect and important scientific research significance and application value in the laser display, laser imaging, laser lighting and other fields.This thesis presents two kinds of visible light combiner based on the photonic crystal, which are all realizes the efficient transmission of three basic colors. The first kind of combiner is based on the photonic crystals line defects. For example, we choose the combining light waves of 635 nm, 532 nm and 488 nm, which are commonly used as three primary colors in laser display systems. We use the theory of photonic crystal coupling model and calculate the coupling length corresponding to different light through theoretical analysis. But in the process of designing of the device, if using the traditional line defect structure, we can see the 635 nm wave only support one mode by observing dispersion curves. In this thesis, we change the dispersion curves by changing the width of the line defects of the photonic crystal. In this way, the 635 nm wave can support two modes. And it also can be a new idea for designing photonic crystal combiner. Using the two photonic crystal directional couplers cascaded mode to realize the three wavelengths of visible light combine. We use finite-difference time-domain(FDTD) method to simulate the wave propagation in the three-wavelength wave combiner, and the size of photonic crystal waveguide also be optimized. The simulation results show that the transmittance of each wavelength can reach above 90%, and the device size is several micrometers.The second kind of combiner is based on the photonic crystals line defects and point defects. The combiner is mainly use of different point defects correspond to different light waves to achieve. Point defect can be a microcavity in photonic crystal,which can make light waves localized in it. By changing the radius size, shape and dielectric constant of the point defect can change the center frequency of microcavity corresponding to the local mode. This thesis mainly uses the line defects and point defects, and set up a microcavity structure, which can improve the transmission efficiency. We use finite-difference time-domain method to simulate the photonic crystal microcavity and waveguide structure. The simulation results for the transmission efficiency can be above 86%, and the size of the device is several micrometers.