Hannover 2020 – scientific programme

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K: Fachverband Kurzzeit- und angewandte Laserphysik

K 5: Laser Systems and Laser Applications

K 5.2: Talk

Wednesday, March 11, 2020, 11:15–11:30, f428

Femtosecond laser generated Mach-Zehnder interferometers based on integrated optical waveguides — •Boldizsar Kassai^{1, 2}, Sabine Tiedeken¹, Volker Braun¹, Ulrich Teubner^{1, 2}, and Hans Brückner¹ — ¹Institut für Laser und Optik, Hochschule Emden/Leer - University of Applied Sciences, Constantiaplatz 4, D-26723 Emden — ²Institut für Physik, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg

Direct writing of optical waveguides in glass by laser exposure deals with at least two unknown parameters: The amount of index modification and the geometry of the waveguide. To solve these problems for guiding structures in Herasil glass, Mach-Zehnder interferometers (MZI) and straight waveguides were generated by direct femtosecond laser radiation (pulse duration 275fs, pulse energy 600nJ, repetition rate 1kHz). All structures are buried 0.1mm deep below the surface. The straight optical waveguides exhibit single mode guiding behavior at 650 nm with nearly circular mode fields and diameters between 5 and 8 microns. The interference signals of asymmetric MZI with short sections of unmodified glass in one path were evaluated at several wavelengths. Thus an effective index increase in the guides of about 0.01 due to laser irradiation was determined. Based on these values, the comparison of the measured mode fields with results from numerical simulations leads to the conclusion of a graded index profile with a maximum of 0.012 and a full 1/e-width of about 0.015 mm. The current results show that MZIs can be used to determine the influences of various laser exposure parameters on index modifications in glass.