| Photonic microstructure is one of the most focused points in modern optics, which can modulate the propagation mode of the light in photonic microstructure by changing artificially the refractive index of optical materials. Photonic microstructure, which can realize the transmission, amplification, detection, sensing of optical signal and so on, can be applied in optical communication, calculation and ultra-fast information processing. In the optical material, the fabrication of integrated photonic chip with various fuctions can promote the miniaturization and integration of optical device. So the fabrication of high-performance photonic microstructure is the basis of integrated photonic chip.The main fabrication methods of photonic microstructure contain ion implantation, femtosecond laser inscription, focused ion beam milling and ion exchange. The structure of photonic microstructure, including multilayer dielectric film, phase grid, optical waveguide, optical microcavity and photonic crystal, has been realized in many optical materials. Thereinto, ion implantation is a mature modification method in the material surface. In the process of ion implantation, the ion beam interacts with the target material, resulting in energe loss of ions and the structural changes of optical material. And in the surface layer of target material, the refractive index changes. By the method of ion implantation, the waveguide structures have been fabricated successfully in more than100optical materials, involving optical crystal, glasses, single crystals, poly-crystalline ceramics, semiconductors and organic materials. Moreover, the focused ion beam can induce the refractive index change of localized area. Femtosecond laser inscription technology employs near-infrared femtosecond laser pulse with high light density to scan optical transparent materials, effecting nonlinear absorption of energe. And then, in the focal volume of the laser pulse, some controlled micro-modifications occur. Concerning the optical properties, in some optical materials, there is an increase of the refractive index in the focal volume. However, in most of the crystals, the femtosecond laser induces a reduction of the refractive index in the focal volume. The focused ion beam milling is a widely used processing method, which can drive the surface atoms out of sample by the charged ions with high energy. The technology is capable of cutting away or building the photonic microstructure (optical microcavity and photonic crystal, etc). By combination of focused ion beam milling and other modification method, the versatile photonic microstructures can be achieved. The technology of ion exchange is based on the ions exchange of sample and solution, to form waveguide area with a high refractive index.The photonic microstructure modulates the transmission mode with the help of refractive index change, so precise control of refractive index is very vital. The select of fabrication method directly affects the optical properties of photonic microstructure. Therefore, the research for fabrication method and waveguiding properties of photonic microstructure is of great significance.In this dissertation, we report on:the fabrication of channel or cladding waveguide structure by femtosecond laser inscription in ZnS, Nd:YAG, KTP crystals; the fabrication of ridge waveguide structure by combination of ion implantation and precise diamond dicing in ZnS crystal; the fabrication of channel waveguide structure by focused proton beam writing in GLS glass; the fabrication of photonic crystal fibre-like with the hole hexagonal array in Nd:YAG crystal by ion implantation and focused ion beam milling. The prism coupling arrangement is used for analysis of waveguide dark-mode. The end-face coupling arrangement is ultilized to measure near-field intensity distributions and propagation losses, and numerical aperture of waveguide structure. By means of the N.A., we can obtain the maximum refractive index change between waveguide region and bulk. And then the reconstructed refractive index profiles can be achieved. The near-field intensity distribution can ben calculated by the Finite Difference Beam Propagation Method (FD-BPM). The BandSLOVE1.3of RSoft software is emolyed to compute the band gap of photonic microstructure in Nd:YAG crystal. With the help of the scanning near-field optical microscope (SNOM) and confocal microscopy, the near-field intensity distribution and luminescent property in the Nd:YAG photonic microstructure can ben obtained. Main results are as follows:Zinc sulfide (ZnS) crystal is an excellent mid-infrared optical crystal. We report on the fabrication of the double-line channel waveguides by femtosecond laser inscription in ZnS crystal. In the wavelength of632.8nm, we analysed transmission properties of the waveguides with different parameters and then find the approach of improving wave-guiding properties.The cladding waveguide structure was fabricated in ZnS crystal by femtosecond laser inscription. We measured the near-filed intensity distribution at the wavelength of4μm by end-face coupling arrangement. Thereinto, the mode in the cladding waveguide structure with diameter of50μm is single-mode. According the reconstructed refractive index profiles, the calculated near-field intensity distributions were achieved by FD-BPM. The experimental results are in good accordance with the calculated ones. The measured minimum transmission loss is～1.1dB/cm.The planar waveguide was fabricarted by ion implantation in ZnS crystal. In order to get ridge waveguide we incised the planar waveguide layer by precise diamond dicing. The end-face coupling arrangement was ultilized to research the transmission properties of ridge waveguides with the width of～30and45μm in the wavelength of632.8nm.Yttrium aluminium garnet (Y3AI5O12or YAG) is a crystalline material with good mechanical property and high transparency (0.4-5.5μm). We report on the fabrication of cladding waveguide structure by femtosecond laser inscription in YAG crystal. The end-face coupling arrangement was employed to measure near-field intensity distribution at the wavelength of～4μm, in good agreement with the calculated results by FD-BPM. The minimum propagation loss for the cladding waveguide structure was measured,～0.7dB/cm.Nd3+doped YAG crystal is one of the best laser gain medium. We report on the fabrication of photonic crystal microcavity with the hole hexagonal array in Nd:YAG crystal by ion implantation and focused ion beam milling. The light intensity enhancement (-30%) at532nm observed at an artificial photonic defect of the structure have been achieved. The result demonstate the wavelength of532nm and 1064nm in the band gap could be confined in the photonic crystal microcavity. The μ-PL intensity enhancement (～5%) at938nm also has been detected. The photonic microstructure can be applied to reduce the threshold, increase the output power and improve the efficiency of waveguide laser.Potassium titanium oxide phosphate (KTiOPO4or KTP) is a low-cost efficient nonlinear optical crystal in the visible to infrared spectral region. We report on the fabrication of cladding waveguides with the shape of semicircle in KTP crystal by femtosecond laser inscription. We employ the end-face coupling arrangement to measure near-field intensity distributions of cladding waveguides with the width of50,120,160μm at the wavelength of～4μm. The guiding properties show very good performance, with single mode or multi-mode behavior for both TE and TM polarizations. The minimum propagation loss of KTP semicircle cladding waveguides is～0.4dB/cm.Sulfide gallium lanthanum (GaLaS or GLS) is a novel chalcogenide glass with excellent optical properties. We report on the fabrication of channel waveguide by focused proton beam writing in GLS glass. The propagation properties have been measured by the end-face coupling arrangement at the wavelength of635,1064,1310and1550nm. The measured near-field intensity distributions are in good agreement with the calculated ones. The minimum propagation loss of GLS channel waveguide is～2.0dB/cm. |
PDF Full Text Request