Characterizations and Applications of Improved Lithium Niobate Ridge Waveguides
Date Issued
2006
Date
2006
Author(s)
Ting, Tien-Lun
DOI
zh-TW
Abstract
In this dissertation, by mixing benzoic and adipic acid as the source of proton exchange, wet etched ridge waveguides are successfully fabricated in LiNbO3. Systematic investigations are put on the fabrication characteristics, etching results, H+ diffusion behaviors, and advantages of relative applications.
In Z-cut LiNbO3, the fabrication process with proposed joint proton source is almost identical to that with pure benzoic acid. In X-cut LiNbO3, however, there exists differentiation. To equally reduce the acidity of both acids, traditional lithium benzoate is no longer suitable for diluting joint proton source, and lithium carbonate is used instead. The etching results show that with certain mole percentages of adipic acid and other things being equal, the etched ridge structures possess larger ridge depths and more vertical ridge sidewalls. Besides, the etched surfaces are still smooth with respect to operating wavelengths, and suitable for producing optical ridge waveguide.
To study diffusion behaviors, secondary ion mass spectrometer (SIMS) along with the Boltzmann-Matano inverse method is used to derive concentration-dependent diffusivity of H+ in Z-cut LiNbO3. With the derived diffusivity, FDTD-based diffusion simulator successfully solves the nonlinear diffusion equation numerically. The etching depths of the experimental results meet well with the simulations. The diffusion model of hydrogen ion in Z-cut LiNbO3 is built and applicable for future use.
For realistic applications, the optical ridge waveguides can be used to fabricate S-bend structure. The experimental results reveal that the lateral confinement of optical field provided by sidewalls of ridge structures is much larger than that of traditional channel waveguides. Thus, the transmission of the S-bend structure can be enhanced. In addition, the sidewalls of samples made by join proton source are more vertical, transmission can therefore further improved. The proposed wet etching method gives an opportunity to shorten the device. In the realm of integrated optics, the practical use is possible.
Subjects
鈮酸鋰
脊形光波導
積體光學
質子交換
溼式蝕刻
氫離子
擴散模型
lithium niobate
optical ridge waveguide
integrated optics
proton exchange
wet etching
hydrogen ion
diffusion model
Type
thesis
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