A single-mode waveguide is fabricated using ion exchange in a molten bath of KNO3 salt. The mode effective index is measured using a mode-lines (M-lines) experiment. The waveguide is then etched, and the M-lines experiment is performed again. The two measurements are sufficient for refractive index profile (RIP) reconstruction, which is assumed to be Gaussian. The reconstructed profile is checked using a numerical technique and is then compared to the inverse technique, showing the inverse technique limitations.
Michael Gad,
Hatem H. ElRefaei,
Diaa A. M. Khalil,
Omar A. Omar,
"Comparison of the N times mode-lines technique to the inverse technique in refractive index profile reconstruction," Optical Engineering 46(9), 094601 (1 September 2007). https://doi.org/10.1117/1.2785177
Michael Gad, Hatem H. ElRefaei, Diaa A. M. Khalil, Omar A. Omar, "Comparison of the N times mode-lines technique to the inverse technique in refractive index profile reconstruction," Opt. Eng. 46(9) 094601 (1 September 2007)