Abstract

Surface roughness is one of the important parameters affecting the optical scattering loss of dielectric waveguides. Despite extensive research interests in correlating optical losses with surface roughness, not much research focus has been dedicated to the study of an accurate metrology and measurement standard for the characterization of waveguide roughness. In this Letter, we report an effective metrology for the measurement of waveguide surface roughness, using confocal laser scanning microscopy (CLSM). We also provide the definition of surface roughness relevant to CLSM terminology based on the measured peak-to-valley (P-V) values, which can be correlated to the conventional root-mean-square roughness, by employing multi-dimensional statistical models. Finally, we demonstrate the use of CLSM metrology in measuring two-dimensional roughness of $10\mathrm{\mu m}\times 6\mathrm{\mu m}$ silica waveguides, showing an average top surface roughness of 0.151 μm and an average sidewall roughness of 0.203 μm. For comparison, the scanning electron microscopy (SEM) measurements are also carried out for the same waveguide samples, and then the measured sidewall roughness values are in the range of 0.08–0.12 μm. Since SEM measures only the amplitude of roughness profile, while CLSM measures the P-V value, after doubling the SEM value, these two methods can provide comparable results of roughness.

© 2019 Optical Society of America

Confocal laser scanning microscopy with spatiotemporal structured illumination

Peng Gao and G. Ulrich Nienhaus
Opt. Lett. 41(6) 1193-1196 (2016)

Confocal fluorescence microscopy for geometry parameter measurements of submerged micro-structures

Merlin Mikulewitsch, Axel von Freyberg, and Andreas Fischer
Opt. Lett. 44(5) 1237-1240 (2019)

Precise in vivo tissue micro-Raman spectroscopy with simultaneous reflectance confocal microscopy monitoring using a single laser

Zhenguo Wu, Liwei Jiang, Wenbo Wang, Jianhua Zhao, Harvey Lui, and Haishan Zeng
Opt. Lett. 44(6) 1383-1386 (2019)

Octave-spanning supercontinuum generation in nanoscale lithium niobate waveguides

Juanjuan Lu, Joshua B. Surya, Xianwen Liu, Yuntao Xu, and Hong X. Tang
Opt. Lett. 44(6) 1492-1495 (2019)

Deep learning enables confocal laser-scanning microscopy with enhanced resolution

Weibo Wang, Biwei Wu, Baoyuan Zhang, Jie Ma, and Jiubin Tan
Opt. Lett. 46(19) 4932-4935 (2021)