Fig. 1. Fabrication methods of LN waveguides: (a) channel guide; (b) ridge guide.

Fig. 2. (a) Dpa profile of 500 keV He ions with the fluence of 1.5 × 10¹⁶ ions/cm² implanted into LN crystal by SRIM 2013; (b) reconstructed RIP of the LN waveguide after annealing at 260°C for 30 min at 633 nm.

Fig. 3. (a) Profile of the TM₀ guided mode simulated by BPM [one-dimensional (1D)]; (b) the modal intensity profile of TM₀ mode computed by the BPM (2D); (c) near-field image of the TM₀ mode by use of the end-face coupling method.

Fig. 4. Optical microscope image (×500) of the end face of waveguides after polishing: (a) WG10; (b) WG15; (c) WG25.

Fig. 5. Reconstructed RIP of the waveguide: (a) WG10; (b) WG15.

Fig. 6. (a)–(c) Near-field image of WG10 quasi-TM modes from the end face of the sample captured by a CCD camera; (d)–(f) modal intensity profile computed by finite difference (FD)-BPM: quasi-TM₀₀, TM₁₀, TM₂₀ modes. The color scale, which represents the relative light intensity, is shown also.

Fig. 7. (a)–(c) Near-field image of WG15 quasi-TM modes from the end face of the sample captured by a CCD camera; (d)–(f) modal intensity profile computed by FD-BPM. The color scale, which represents the relative light intensity, is shown also.

Fig. 8. Experimental setup used with the end-face coupling method. Obj, microscope objective lens; location 1, the first position where the light power was measured; location 2, the second position where the light power was measured.