Nanooptics and photonics

An effective method of nano-polishing of quartz substrates
Vasylenko D.O., Kravchuk P.O., Grygoruk V.I.
Faculty of Radio Physics, Electronics and Computer Systems of Taras Shevchenko National University of Kyiv
Volodymyrska Str., 64/13, Kyiv-01601, Ukraine
E-mail: vda7@ukr.net

We applied a drop of NaClO to the quartz substrate. Then the substrate was irradiated by a laser (λ = 532 nm) from below at an angle of total internal reflection, because of which an evanescent wave formed on its surface. The evanescent wave causes the decomposition of the hypochlorite anion ClO–. As a result, formed an atomic chlorine, which is able to react with quartz. The SiO2 particles and the formed atomic chlorine Cl are polarized by an evanescent wave. The resulting dipoles generate all three components (namely ~1/r3, ~1/r2 and ~1/r) of the electric field [1]. The vector of the electric field of the evanescent wave is always directed orthogonally to the surface plane. The dipoles of Cl and SiO2 are oriented along the same straight line and unlike poles to each other. In this case, the interaction of Cl and SiO2 dipoles is due to the strongest in the near zone component of ~1/r3, unlike the previous experiments of photochemical nano-polishing [2-4], where the substrate was irradiated from above, orthogonally to the surface plane, and the dipoles of Cl and SiO2 were oriented in parallel, equatorial regions to each other. With such a mutual arrangement of dipoles, their interaction was due to the much weaker in the near zone component of ~1/r2.
The surface roughness of the quartz substrate was markedly reduced with the use of the nano-polishing method proposed by us. During 20 minutes of nano-polishing, the values of roughness parameters decreased as follows: Ra from 56.33 nm to 27.33 nm (by 2.1 times), Rz from 247.51 nm to 138.51 nm (by 1.8 times) and Rmax from 317.22 nm to 156.22 nm (by 2 times).

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