Guide-Wave Optical Properties Of Energetic Ion Irradiated Silicon Carbide And Disordered Crystals

Integrated optics is a burgeoning discipline, which is based on microelectronics developed in the 20th century and optoelectronics. It utilizes integrated approach to investigate and develop optoelectronic devices and composite optoelectronic devices. As we all know, the traditional optical system cannot adapt to the development of modern photovoltaic technology owing to its bulky size, poor stability and beam collimation adjustment difficulties. In 1969, Dr. S. E. Miller presented the concept of integrated optics, and it focus and expands the inherent technological advantages of optical and microelectronics. Integrated optics changes the traditional optoelectronic system consisted of discrete device to integrated optical systems, and mainly researches integrating active devices (e.g., laser, modulators) on the same substrate material, and connects passive components (e.g., optical waveguide, couplers) to compose miniature optical system, which can effectively achieve miniaturization, integration and thin film optical system. Optical waveguide structure is a fundamental part of integrated optics, which is composed of high refractive index region wrapped by lower refractive index region. It relies on the principle of total reflection to limit the transmission of light waves. Right now a variety of techniques have been reported to produce optical waveguides with different structures in optical crystals, such as planar waveguide and channel waveguide.For practical purposes, it is essential to fabricate perfect and flexible optical waveguide structure. Up to now, there have been a variety of methods to be used in the preparation of an optical waveguide structure on crystalline materials. For instance, planar waveguide can be fabricated in various crystals with energetic ion beams irradiation. For energetic ion beams irradiation technique, charged ions with certain energy were injected into the surface of the crystal material. After charged ions go into the substrate material, it will collide with the nuclear or electrons of the target atoms in target material, thus losing energy to cause the lattice structure damage of substrate material and forming the optical waveguide structure with the refractive index change in substrate material. According to different relative numbers atoms of the incident ions, energetic ion beam irradiation technology has been divided into the ion implantation technique and swift heavy ion irradiation techniques. Ion implantation technique usually employs relative light ion, consisting of hydrogen (H) and helium (He) ions. Swift heavy ion irradiation uses so-called heavy ions, generally referring to the energetic no less than 1MeV/amu, e.g., carbon (C), nitrogen (N), and oxygen (O). The most significant advantage of this method is the wide applicability of materials. Meanwhile, this technique in combination with femtosecond laser etching technique or precision diamond blade dicing could be used to fabricate channel waveguides.In this dissertation, energetic ion beam irradiation was used to fabricated planar waveguides in 4H-SiC crystal and disordered crystals and then, femtosecond laser etching or precision diamond blade dicing was employed to micro-manufacture ridge waveguides. A series of experiments had been carried out to measuer and investigate guide-wave properties of optical waveguides structure, including near-field propagation modes, refractive index distribution, propagation losses, Raman spectrum and micro-luminescence properties. According to the different material the work and results of this dissertation are summarized as following:Planar waveguide structure is fabricated in 4H-SiC single crystal by swift heavy ion irradiation, and then ridge waveguides have been formed by femtosecond laser etching on the planar waveguide with different parameters. The near-field modal intensity distributions exhibit the well-confined light propagation in the waveguides, and the maximum transmittance wavelength is at～900 nm. The minimum propagation loss, as low as 5.1 dB/cm, has been achieved by using the single-scan fs ablation. The investigation of confocal micro-Raman spectra suggests partial transition of 4H-SiC to 6H-SiC in the irradiated region.Ridge waveguides have been produced in Nd.CNGG disorder laser crystal by using precise diamond blade dicing of carbon ion irradiated planar waveguide. The propagation loss of the ridge waveguide is measured to be～3.8 dB/cm at the wavelength of 632.8 nm. The micro-Raman spectrum indicates that the microstructure of the Nd:CNGG crystal has no significant change after carbon ion irradiation. The microphotoluminescence feature has been found well preserved in the waveguide structure. The thermal stability of the waveguide has been investigated, showing relatively stable feature below 260℃.Planar waveguides in Nd:BaLaGa3O7 and Nd:SrLaGa3O7 crystals are fabricated by carbon ions implantation, and then ridge waveguides have been formed by precision diamond blade dicing on the planar waveguide. The near-field intensity distributions in the visible and near-infrared bands are detected and single mode guiding is observed at the wavelength of 1550 nm. The propagation losses of the planar waveguide are measured to be as low as 1.6 and 2.5 dB/cm in Nd:BaLaGa3O7 and Nd:SrLaGa3O7 crystals at 632.8 nm. The micro-Raman property of the materials in the waveguide regions are discussed in detail, which are proved to be well preserved in the waveguides.