The Investigation On Optimization Of Ion-Implanted Planar And Channel Waveguides

The optical communication technology has become a swiftly developing and synthetized technical domain. As the most fundamental intergral part of the integrated optics circuits, the optical waveguide structure is of great importance in the field of modern optical communication. The researchers are always looking for the effective methods to fabricate waveguides possess excellent performances. At present, the most popular methods include diffusion, exchange, film deposition and ion implantation etc. The ion implantation method is not sensitive to the structure of the substrate materials. Up to now, people have formed optical waveguide structures in masses of optical materials such as optical crystals, glass, semiconductors etc. The ion implantation has become an effective method to fabricate optical waveguide.The ion implantated waveguide technology is sorted to two different strategies named light-ion implantation and heavy-ion implantation, according to the mass of the implanted ions. The ions used in the light-ion implantation are proton or the Helium ions, however, the ions used in the heavy one are C, O and Cu etc. The light-ion implantation requires higher dose than the heavy-ion implantation to form the waveguide structure. In some materials, dose of only 10¹³ions/cm² magnitude is sufficient for the heavy-ion implanted waveguide formation.Due to the different mass of the injected ions used in two methods, the light-ion implantated waveguides and heavy ones formed in optical crystals are distinct. When the light-ions implanted into the crystal substrate, an optical barrier with a lower refractive index compared to the substrate will be formed by the deposition of the implanted ions, leaving a nearly undisturbed region between the optical barrier and the surface. So this type of waveguide is comprised by the air, the optical barrier and the undisturbed region. When the heavy ions implanted into the crystal, the electronic energy loss (ususlly small in light-ion implantation) is strong enough to change the optical properties of the surface. This change surely weaks the birefringence of the implanted region, resulting in the increase of the lower refractive index. The light confinement ability of this type of waveguides relies on the enhanced refractive index layer so that they are sensitive to the polarization direction of the light.The ion implantation can also form waveguides in some optical glasses. The glass substrates will suffer compaction under the influence of both nuclear damage and electronic effects. So the implantation produces enhaced index optical wells to form the waveguide in these materials.In this dissertation we report the waveguide formation and characterization on stoichiometric LiNbO₃, congruent LiNbO₃, BiBO, Nd³⁺ doped silicate glass, Nd:YVO₄ and fused silica. The prism coupling method is used to measure the dark mode spectra of the implanted waveguides. The end-fire coupling method is used to get the near-field profile and the propagation loss of the waveguides. The refractive index profile is obtained by the simulation of the effective refractive indices of the waveguides. The RBS/Channeling measurements are performed to investigate the SLN waveguide formed by MeV Si ion implantation. The channel waveguide is fabricated by ion implantations plus the photolithography process in stoichiometric LiNbO₃, congruent LiNbO₃, Nd³⁺ doped silicate glass and Nd:YVO₄.LiNbO₃ is an important and promising waveguide material because of its outstanding nonlinear optical and electronic-optic properties. We usually called the congruent LiNbO₃ LN crystal. The ratio of Li/Nb in congruent LiNbO₃ is smaller than 1:1 and so there are a lot of defects in congruent LiNbO₃ crystal. As a result, the optical performances of congruent LiNbO₃ are reduced. Nevertheless, the ratio of Li/Nb in stoichiometric LiNbO₃ is upgraded. Stoichiometric LiNbO₃ shows a very improved performance because of the much fewer defects in the crystal compared to congruent LiNbO₃. By using the 2.8 MeV Si ion implantations, we have fabricated waveguides in SLN with an extraordinary refractive index enhanced layer. The damage induced by implantation has been analyzed by RBS/Channeling measurements. The RBS results show that Si ion implantation caused a little damage to the structure of SLN and the damage will be almost elimated by the post-annealing treatment. By using O ions with different energies, the waveguides were fabricated in CLN samples. The annealing treatments are performed to reduce the propagation loss of the waveguide. The mode polarization properties in two different waveguides formed by 6 MeV C ions ans 3.6 MeV O ions, respectively, were analyzed. The near field profiles of these waveguides were measured by end-fire coupling method. The refractive index profiles of these waveguides were calculated by the RCM code. The channel waveguide and planar waveguide were fabricated in SLN crystal by using 6 MeV O ion implantation at dose of 5×10¹⁴ions/cm² plus the photolithography process. The near-field profiles of different modes in channel waveguide were obtained by using end-fire coupling method. The refractive index profiles of no and ne indices of the planar waveguide were reconstructed by the simulation of the effective refractive indices by using RCM code. The planar waveguide was formed in SLN by using 500 keV proton at a dose of 1×1017 ions/cm2. Additionally, the selective etching in the positive z face of LiNbO₃ crystal was performed after the MeV O and Si ion implantations.BiBO crystal is an outstanding nonlinear crystal. BiBO has large effective nonlinear coefficient, high threshold of optical damage. BiBO can be easily grown into big and well-proportioned crystal. Additionally, it's non-deliquescent. Due to its excellent chemical and nonlinear optical performances, BIBO has a great potential in nonlinear optical field. In this dissertation, we report the waveguide formation by using 3.6 MeV O ions at doses from 5×10¹² ions/cm² to 5×10¹³ ions/cm² and 3.0 MeV O ions at doses from 5×10¹² ions/cm² to 5×10¹³ ions/cm², respectively. The index enhance layer can be found in n_x and n_y directions within these waveguides. By using RCM code, the refractive index profiles of these waveguides were reconstructed.Silicate glass based on SiO₂ is one of important optical materials. It has good mechanical performance, high chemical stability and very high transparency in infrared wavelength. Since its high solubility for rear earth ions such as Nd³⁺ and Er³⁺ ions, it has been extensively used as host of waveguide amplifier and waveguide laser. Nd³⁺-doped silicate glass can provide gain near 1.3μm. We report on the fabrication and characterization of low-loss planar and stripe waveguides in Nd³⁺-doped glass by 6MeV oxygen ion implantation at a dose of 1×10¹⁵ ions/cm². The dark mode spectroscopy of the planar waveguide was measured using a prism coupling arrangement. The refractive index profile of the planar waveguide was reconstructed from a code based on the reflectivity calculation method. The results indicate that a refractive index enhanced region as well as an optical barrier have been created after the ion beam processing. The near-field mode profiles of the stripe waveguide were obtained by an end-fire coupling arrangement, by which three quasi-transverse electric modes were observed. After annealing, the propagation losses of the planar and stripe waveguide were reduced to be～0.5 dB/cm and～1.8 dB/cm, respectively. Channel waveguides were also fabricated by 6 MeV C ions implantation as dose of 5×10¹⁴ ions/cm². We report on the fabrication of optical channel waveguides in Nd:YVO₄ crystal produced by photographic masking and following direct O ion implantation at 3.0 MeV. Annealing treatments of the samples are performed to improve the waveguide stability and to reduce propagation losses. An increase of the ordinary retractive index induced by the implantation is believed to be responsible for waveguide formation. Quasi-TM guided modes are observed while no quasi-TE ones are detected. The optical damping coefficients are of 0.43, 0.63, and 0.54 cm^-1 for channel waveguides with widths of 4, 5, 6μm, respectively. The results of modal analysis are in agreement with the experimental data.Fused silica is widely used in the manufacture of optoelectronics devices because ofits low thermal conductivity, high electrical receptivity and excellent properties optics and mechanics. The coupling between fused silica and optical fiber is much easier because of the small difference between their refractive indices. Therefore the fused silicate has been frequently employed as substrate for many integrated optical devices. The planar waveguides have been produced in fused silica by 2.4 MeV C⁺ ion implantation at a dose of 1×10¹⁵ ions/cm² at room temperature. The effective refractive indices of the guided modes are measured by the prism-coupling method at wavelength of 632.8nm and 1539nm, respectively. The index profile is reconstructed by reflection calculation method. The mode propagation of the waveguides is solved with a code based on beam propagation method. To make a contrast to the carbon implantation, we report the fused silicate waveguide formed by much lighter ion- 500 keV proton implantation at a dose of 1×10¹⁷ ions/cm². We measure the thermal stability by anneal the sample at different temperatures and times. The propagation losses were measured by Back-reflection method. The results show that the planar waveguide in fused silicate formed by 500 keV proton implantation at a dose of 1×10¹⁷ ions/cm² has an excellent thermal stability. The propagation loss can be reduced by annealing treatment.