The Investigation On Waveguide In Yttrium Vanadate By Ion Implantation Adn Its Photonic Crystal Slab Structure

The main contents of Wave Guiding Optics are transmission characteristics and propagation phenomenon of light in waveguides, in addition, designing, fabrication and connection of optical waveguide devices. The key object of Wave Guiding Optics is planar optical waveguide, which is the basic struture of many passive components, such as optical couplers, light modulator, photo-detector, and so on. Optical waveguides consist of a square or rectangular core surrounded by a cladding with lower refractive index than that of the core. There were several methods to fabricate waveguide, such as, deposition of thin film, ion exchange, ion diffusion, ion implantation, femoto-second laser writing, and so on. We used ion implantation in our experiment. Ion implantation includes light ion implantation with large fluence (such as H and He ion) and heavy ion implantation with low fluence (such as O, Si, and Cu ion, etc). Generally speaking, the formation mechanisms of two types of wavegudes are different. In the waveguide formed by light ion implantation, a damage area with lower refractive index (optical barrier) generated by nulear energy deposition at the end of ion range, and a waveguide structure formed between air and the optical barrier. In the waveguide formed by hearvy ion implantation, not only an optical barrier forms at the end of ion range, but also an increase of refractive index occurs in the near-surface region.Photonic crystal is structure with periodic dielectric arrangement. Photonic crystal is optical analogue of crystal. Crystal is a periodic arrangement of atoms or molecules, which presents a periodic potential to electrons propataing through it. In some case, the periodic potential prohibits the propagation of certain electron waves. In photonic crystal, the atoms or molecules are replaced by macroscopic media with diffrent dielectric constans, and the periodic potential is replaced by a periodic dielectric function. We can design and construct photonic crystal with photonic band gaps, which prevent light propagating in certain directions with specified frequencies. If, for some frequency, a photonic crystal prohibits the propagation of light of any polarization from any direction, we say that the photonic crystal has a full photonic band gap. Within the photonic band gap, no modes are allowed; the density of states is zero. By perturbing the arrangement of the photonic crystal, we can create localized mode that have frequencies within the gap. Considering the inhibited spontaneous emission of the photonic band gap, we can fabricate photonic crystal emitting diode with good monochromaticity; Photonic crystal can be used to design ideal photonic crystal fibers, photonic crystal waveguide, photonic crystal laser, photonic crystal filter, photonic crystal splitter, photonic crystal superprism, and solar cells, etc.There are several methods to fabricate photonic crystal, such as the mechanical drilling method, accumulating of dielectric medium, electron beam lithography, self-assembly method, and laser holographic lithography. Although the fabrication of three dimensional photonic crystals has gained great achievements, there are still many problems, such as accuracy, the high cost, and application etc. Fabrication of three dimensional photonic crystals is very difficult. However, photonic crystal slab is much easier to made, which combines the two dimension photonic crystal structure with planar waveguide. Photonic crystal slab has only two dimensional periodic dielectric arrangements and using index guiding in the third direction.Yttrim orthovanadate (YVO4) is a good artificial crystal, with wide transparency (0.4μm to5μm), good temperature stability, excellent physical performance and mechanical properties, large birefringence (Δn=0.222at0.633nm). It can be used to produce ideal optical components such as fiber optical isolators, circulators, beam displacers and other polarizing optical devices. Nd:YVO4is an excellent material for laser application because of its advantageous spectral characteristics, such as greater laser emission cross section, lower laser threshold, and higher efficiency.There have been YVO4and Nd:YVO4waveguides formed by ion implantation previously, however, multimode optical waveguides exhibit modal dispersion resulting from multiple spatial modes, while, single mode waveguides have narrower modal dispersion. Therefore, single mode waveguides are better at retaining the fidelity of each light pulse and single mode waveguides have larger bandwidth than multimode waveguides. In this work, we made single mode planar waveguide in YVO4and Nd:YVO4by He and oxygen ion implantation. We fabricated the ridge waveguide on the planar waveguide by photolithographic technique and Ar ion beam etching. On the planar and ridge waveguide, we made photonic crystal structure by focus on ion beam (FIB) technique. We tried bonding YVO4on SiO2substrate by smart cut method. We simulated the band diagram of photonic crytal slab structure of "YVO4on SiO2" using the plane wave expansion method and the finite difference time domain method. The main results of this thesis are shown as following:1. The single mode planar waveguide in YVO4formed by He ion implantationWe fabricated single mode planar waveguide in z-cut YVO4by400keV,500keV He ion implantation in fluence of3×1016ions/cm2at room temperature or at liquid nitrogen temperature (77K). We investigated annealing behavior of the guiding mode and near-field image in the waveguide by prism-coupling method and end-face coupling method respectively. The Rutherford Backscattering/Channeling (RBS/C) technique was used to investigate the damage reduction after annealing treatments. We reconstructed the refractive index profiles in the waveguide under different condition by applying intensity calculation method (ICM).2. Planar waveguide formed by muli-energy light ion (He and H) implantationWe fabricated single mode planar waveguide in z-cut Nd:YVO4by multi-energy (450,500,550keV) He ion implantation to total fluence of4.5×1016ions/cm2at room temperature. We aslo fabricated planar waveguides in Nd:YVO4by multi-energy (480,490,500keV) proton implantation to a total fluence of4.5×1016ions/cm2at room temperature. Damage behaviors of Nd:YVO4waveguides after implantation were investigated by the RBS/C technique. We investigated optical properties of Nd:YVO4before and after ion implantation by measuring transmission, confocal micro-luminescence,and confocal Raman spectra. Absorption bands and the photoluminescence features of the bulk Nd:YVO4crystal have been preserved after ion implantation. In Raman spectra, most of peak positions and peak widths had no obvious change before and after ion implantation.3. Single planar waveguide in YVO4(Nd:YVO4) formed by oxygen ion plantationIn order to investigate the effect of ion fluence, we made single planar waveguide by1MeV oxygen ion implantation in fluence of0.5×1015ions/cm2.1.0×1015ions/cm2, and1.5×1015ions/cm2, respectively. To investigate the effect of ion energy, we fabricated single planar waveguide by2MeV and3MeV oxygen ion implantation, respectively. We also compared the transmission spectra of Nd:YVO4waveguides formed by different energy. We found that the absorption band edge has some red shift after oxygen ion implantation, and the red shift is more obvious for higher energy. The transimission coefficient decrease with the increase of energy. The reason was that more color centers form for higher energy when the oxygen ion range is deeper.4. Photonic crystal structure fabricated on YVO4waveguide by FIBWe fabricated photonic crystal structure in cubic and hexagon unit on YVO4waveguide by focused ion beam (FIB) technique. We investigated effects of ion beam condition, depth, gas, and structure size. We found that collapse is more prone to happen in the hexagon unit photonic crystal sturcure; the etching rate increase along with the increase of the beam; Because of the redeposition effect, the actual etching depth is always less than the default etching depth; the auxiliary gas can not significantly improve etching shape; the etching time grow with the increase of the photonic crystal structure size; the redeposition makes the hole bottom tend to be flat for larger size photonic crystal structure, and the redeposiont make the expected cylindrical holes to be conical for smaller size photonic crystal structure; collapse tend to happen for larger filling fraction, and conical holes prone to happen in smllaer filling fraction. 5. Fabrication of "YVO4on SiO2" by smart cut methodWe tried bonding YVO4on SiO2substrate by smart cut method, and then, we observed the surface morphology of YVO4on SiO2by optical microscope, we measured the depth of the YVO4film by AFM (Atomic Force Microscopy). In addition, we analysed the composition of film on SiO2by the Rutherford Backscattering technique. We simulated the band diagram of photonic crystal slab structure of "YVO4on SiO2" using the plane wave expansion method (PWE) and the finite difference time domain method (FDTD).