Mev Heavy Ion Implanted Lithium Niobate <sub> 3 </ Sub> And Ktp Waveguide Preparation And Research

Lithium niobate is one of the most widely used materials for integrated optics due to its excellent optical, piezoelectric, electro-optic, elastic, photoelastic and photorefractive properties. Waveguide devices based on LN have been widely used especially in the fields of optoelectronics and telecommunication. Comparing to the conventional waveguides fabrication techniques such as diffusion and ion exchange, implantation exhibits its unique advantages.In all the implanted LN waveguides, MeV He and H ions are most frequently used. The dose of ion beam is in the range of a few times 10¹⁶ ions/cm². In the case of light ion implantation, a reduced-index layer (barrier) is formed at the end of the ion track and the layer between barrier and surface works as a light guiding region. Light ion implanted LN waveguides have been demonstrated to be typical barrier-confined multimode ones.However, the situation is different when heavy ion implantation is performed. In 2002, Hu et al. reported that a single mode waveguide in LN was formed with a low Si beam dose implantation. The single mode is confined by raised extraordinary index in the surface layer, which is regarded as a guiding region. Because of the similar characteristic of raised extraordinary index in guiding layer, such a waveguide is comparable with the waveguide formed by exchange or diffusion.Waveguide formation by the heavy ion implantation shows two advantages: (1) the beam dose is extremely low, usually in the range of a few times 10¹³-10¹⁴ ions/cm², which makes the implantation process much shorter than that of light ion implantation; (2) MeV heavy ion implantation forms the barrier located only 1-1.5 μm beneath the surface, and a single mode waveguide is achieved more easily.In order to understand how the beam dose dominates the formation of waveguides, we performed the following experiments given both ion and energy are definite.We formed waveguides on LN substrate by 3.0 MeV nickel ions implantation withdifferent beam doses from lxlO13 to 9xlO14 ions/cm2. Single mode waveguide from raised extraordinary index layer was formed and the loss of such waveguide was about 3 dB/cm. A "mode missing" in a certain range of implanted beam dose was observed. Below this range of beam dose, the waveguide with raised extraordinary index in the surface layer or barrier-confined waveguide with low ordinary index in damaged layer may be formed. If the dose is higher than this range, only barrier-confined waveguide can be formed. The possible surface waveguide devices may be fabricated based on the low dose and single energy implantation technique. The loss of the barrier-confined waveguide mode with a dose of 8xlO14 ions/cm2 was reduced from 1.65dB/cm to 1.19dB/cm after annealing at 300°C for 30min.And then we formed waveguides on LN substrate using other heavy ions with different energy and dose to find the optimal conditions achieving LN single-mode waveguides.We formed a single-mode waveguide in LN crystal by 2.0 * 1.5 and 1 .OMev O ions implantation with flounces from 1.5xlO14 to 4xlO14 ions/cm2. A bright line in the wavelength of 632.8nm was observed only when moderate postimplant annealing was performed. The possible index profile of the waveguide was constructed according to the damage profile of the lattice structure caused by the implantation. Although dark-mode measurement showed that the effective extraordinary index of LN was raised in the waveguide layer, results of the analysis indicated that the single guiding mode could be supported by a synergetic effect from both the raised index layer and the low-index barrier. The reduced loss of the waveguide can be attributed to the widened low-index barrier from multienergy implantation. We also formed waveguides by 4.5 ^ 3.6 and 3Mev O ions implantation with flounces from 0.9xl014 to 7.2xlO14 ions/cm2 and analyzed waveguides mode and the annealing behavior.