Near-stoichiometric Ti:LiNbO3 strip waveguide with varied substrate refractive index in waveguide layer
Zhang De-Long(张德龙)a)b)† , Wu Chang(吴嫦)a), and Pun Edwin Yue-Bun(潘裕斌)b)
a School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China, and Key Laboratory of Optoelectronics Information Science and Technology, Ministry of Education, Tianjin 300072, China; b Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, China
Abstract We report the near-stoichiometric Ti:LiNbO3 strip waveguides fabricated by vapour transport equilibration (VTE) at 1060 C for 12 h and co-diffusion of 4--8 m wide, 115-nm thick Ti-strips. Optical studies show that these waveguides are monomode at 1.5 m and have losses of 1.3 and 1.1 dB/cm for the TM and TE modes, respectively. In the waveguide width/depth direction, the mode field follows a Gauss/Hermite--Gauss profile. A secondary ion mass spectrometry study reveals that the Ti profile follows a sum of two error functions along the width direction and a complementary error function in the depth direction. Micro-Raman analysis shows that the Li-composition in the depth direction also follows a complementary error function. The mean Li/Nb ratio in the waveguide layer is about 0.98. The inhomogeneous Li-composition profile results in a varied substrate index in the guiding layer, and the refractive index profile in the guiding layer is given.
Fund: Project supported by the National
Natural Science Foundation of China (Grant Nos. 50872089 and
60577012) and the Research Grants Council of the Hong Kong Special
Administrative Region, China (Grant No. CityU 1194/07).
Cite this article:
Zhang De-Long(张德龙), Wu Chang(吴嫦), and Pun Edwin Yue-Bun(潘裕斌) Near-stoichiometric Ti:LiNbO3 strip waveguide with varied substrate refractive index in waveguide layer 2010 Chin. Phys. B 19 024214
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