M-line spectroscopic, spectroscopic ellipsometric and microscopic measurements of optical waveguides fabricated by MeV-energy N+ ion irradiation for telecom applications

Abstract

Irradiation with N+ ions of the 1.5 -3.5 MeV energy range was applied to optical waveguide formation. Planar and channel waveguides have been fabricated in an Er-doped tungsten-tellurite glass, and in both types of bismuth germanate (BGO) crystals: Bi4Ge3O12 (eulytine) and Bi12GeO20 (sillenite). Multi-wavelength m-line spectroscopy and spectroscopic ellipsometry were used for the characterisation of the ion beam irradiated waveguides. Planar waveguides fabricated in the Er-doped tungsten-tellurite glass using irradiation with N+ ions at 3.5 MeV worked even at the 1550 nm telecommunication wavelength. 3.5 MeV N+ ion irradiated planar waveguides in eulytine-type BGO worked up to 1550 nm and those in sillenite-type BGO worked up to 1330 nm. According to our previous investigations [7], MeV energy N + irradiations at high fluences resulted in the formation of a barrier layer around the stopping range of the ions. The fluences indicated in Table 1 were appropriate to obtain sufficiently large refractive index difference between the well and the barrier for guiding. The Guest Editor 3) The waveguide losses can be measured by using back-reflection method even for short samples. Any method for ion implanted waveguide has its own advantages and shortcomings. The authors should not expect too much from longer samples. For high-loss waveguides, the surface scattering method reflects sometimes very wrong results.We have made the following modifications to comply with the above request:We added the following sentence to Chapter 6. Conclusion, on page 18 line 5:Besides of the double prism method, propagation losses will be measured by the backreflection method, too. 4) Only showing the modal lines is a not a direct proof for a real waveguide. For some ion implanted waveguides, one can detect beautiful modes, but the light cannot go through the waveguides with a simple end-face coupling system. So what I suggest for the future work is not to make more samples but to first test the propagation (transmission) of light in the waveguide. This can be stated in the Conclusion section.We have made the following modifications to comply with the above request:We added the following sentence before the last sentence of the 6. Conclusion Chapter: 2.Issues raised by Reviewer #2: Firstly the paper is not particularly well written. The introduction does not critically review past studies and as a result it is not clear how this present study is novel or different.Since this article is not a review, detailed discussion of previous art is outside its scope. This article is based on an oral presentation given at Symposium W-Current Trends in Optical and X-Ray Metrology of Advanced Materials for Nanoscale Devices III of the 2012 Spring meeting of the EMRS Society, our aim was to present the following novelties of our results:1. Application of spectroscopic ellipsometry to the quantitative study of (ion beam irradiated) planar optical waveguides 2. Comparison of the spectroscopic ellipsometric results with the predictions of SRIM simu...