title: Polarization-insensitive, shallow Ti-diffused near-stoichiometric LiTaO3strip waveguide for integrated optics.
abstract: We report on a Ti-diffused near-stoichiometric (NS) LiTaO3strip waveguide fabricated by diffusion of an 8 μm wide, 160 nm thick Ti-strip followed by Li-rich vapor transport equilibration. It is found that the waveguide surface caves in ∼60  nm below the crystal surface. X-ray single-crystal diffraction shows that the indentation is due to Ti-induced lattice contraction. Optical studies show that the waveguide is in an NS composition environment, supports TE and TM single-mode propagation at 1.5 μm wavelength, is polarization insensitive, and has a shallow mode field profile and a loss of 0.2/0.3 dB/cm for the TE/TM mode. Secondary ion mass spectrometry analysis shows that the Ti profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of the waveguide. With the optimized fabrication condition, the waveguide is promising for developing an optical-damage-resistant device that requires a shallow mode field profile.
authors.forename: Xiao-Fei
authors.initials: XF
authors.lastname: Yang
authors.forename: Zi-Bo
authors.initials: ZB
authors.lastname: Zhang
authors.forename: Wan-Ying
authors.initials: WY
authors.lastname: Du
authors.forename: Qun
authors.initials: Q
authors.lastname: Zhang
authors.forename: Wing-Han
authors.initials: WH
authors.lastname: Wong
authors.forename: Dao-Yin
authors.initials: DY
authors.lastname: Yu
authors.forename: Edwin Yue-Bun
authors.initials: EY
authors.lastname: Pun
authors.forename: De-Long
authors.initials: DL
authors.lastname: Zhang