伽瑪射線對光波導特性之研究

Characterization of Gamma-Ray Irradiated Optical Waveguides

賴政志(Cheng-Chih Lai)

指導教授 ： 王維新

國立臺灣大學/電機資訊學院/光電工程學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.02575

摘要

本論文主要探討伽瑪射線對光學材料特性的影響與應用，並有系統進行深入研究與分析。就光學材料部分，本論文選取高分子材料苯並環丁烯和鐵電材料鈮酸鋰作為主要研究的課題。
就鈮酸鋰而言，我們首先製作鈦擴散、鎳擴散、鋅鎳擴散、質子交換和退火形質子交換等五種不同的光波導，並使用633nm、1300nm和1550nm等三種不同的波長來研究伽瑪射線對鈮酸鋰導波特性之影響。就應用部分，我們也發現藉由伽瑪射線的照射，使得鈮酸鋰溼式蝕刻的深度較傳統溼式蝕刻的深度增加二至三倍，且脊形側壁所增加的光場橫向侷限性較傳統平面通道式波導大，元件之傳輸率因此明顯上升，在積體光學元件上有實用價值。
對高分子材料BCB而言，從研究過程中發現隨著伽瑪射線照射量的增加，其模態折射率也會隨之改變，同時我們也發現當高分子材料BCB覆蓋一層金屬薄膜，其模態折射率之改變量與有無覆蓋金屬不同，針對此一特性本研究製作一高分子波導，並量測其光學特性。此種新製造出之高分子光波導侷限性比用電子束直接寫方式佳，在未來積體光學元件的研究與製作上提供了另一種選擇。伽瑪射線對其他光學材料特性的影響及其應用也將成為未來有趣的研究題材。

關鍵字

伽瑪射線 ； 苯並環丁烯 ； 鈮酸鋰 ； 溼式蝕刻 ； 脊形結構 ； 高分子波導

並列摘要

In this dissertation, the characteristics and application of gamma-ray irradiated optical material are studied. In particular, polymer material benzocyclobutene (BCB) and the ferroelectric material lithium niobate (LiNbO3) are chosen for interest.
For LiNbO3, five waveguides fabricated by Ti-diffusion, Ni-diffusion, Zn and Ni co-diffusion, proton-exchange, and annealed proton-exchange are chosen. And lasers of wavelengths 633nm, 1300nm, and 1550nm are employed for the characterization of the waveguides. Experimental results show the height of wet etched ridge structure on the LiNbO3 substrate is 2-3 times higher with than without gamma-irradiation. As the lateral optical confinement provided by sidewalls of ridge structures is enhanced, the optical power transmission is increased, which is certainly useful for the improvement of integrated optical devices
For BCB samples, experimental results show that the modal refractive index change is increasing with the dosage of gamma irradiation before it is seriously damaged. Moreover, the modal refractive index changes with and without a metal mask are found slightly different. With the small difference in refractive indices, novel BCB waveguides and devices are successfully fabricated. The optical fields are better confined in the proposed BCB waveguides than those in e-beam direct written ones. That provides an alternative method of waveguide fabrication for integrated optical devices. Details of the characteristics and application of the proposed gamma irradiation on other optical materials will be of great interest for future study.

並列關鍵字

gamma-ray ； benzocyclobutene (BCB) ； lithium niobate (LiNbO3) ； wet etched ； ridge structure ； polymer waveguide

參考文獻

[1]R. G. Hunsperger, Integrated Optics: Theory and Technology, 5th ed., Springer, 2002.

[2]C. Y. Chang, C. C. Lai, and W. S. Wang, “Variable TE-TM mode splitter using nickel diffusion and annealed proton-exchange lithium niobate waveguide,” revised by Japan J. Appl. Phys.

[3]A. Holmes-Siedle, “Radiation effects in space, nuclear power and accelerators : impact on optics and light sensor,” SPIE Critical Review of Science and Technology on Advancement of Photonics for Space, vol. CR66, pp. 37-57, 1997.

[5]E. Voges and A. Neyer, “Integrated-optic devices on LiNbO3 for optical communication,” J. Lightwave Tech., vol. 5, pp. 1129-1238, 1987.

[6]G. J. Griffiths and R. J. Esdaile, “Analysis of titanium diffused planar optical waveguides in lithium niobate,” IEEE J. Quantum Electron., vol. 20, pp. 149-159, 1984.