Direct measurement of the guided modes in LiNbO[sub 3] waveguides

Campillo, A. L.; Hsu, J. W. P.; White, C. A.; Jones, C. D. W.
April 2002
Applied Physics Letters;4/1/2002, Vol. 80 Issue 13, p2239
Academic Journal
Mode profiles of the light coming out of Ti diffused waveguides formed in LiNbO[sub 3] crystals were imaged using a near-field scanning optical microscope (NSOM). We find that the transverse magnetic mode has a smaller spatial dimension and is closer to the surface of the waveguide than the transverse electric mode. We also measured the phase and intensity distributions of the guided optical modes directly by incorporating the NSOM into an interferometer. The effective index (n[sub eff]) is determined from the spacings of phase fronts, which equals λ/n[sub eff]. The experimental results of mode profiles and n[sub eff] are in good agreement with theoretical simulations. However, an unexpected nonuniform intensity distribution was observed, which could be linked to defects in the waveguide.


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