Tailoring Properties of Microcavity In-Line Mach-Zehnder Interferometer by the Microcavity Enlargement Using Femtosecond Laser

• Published in: Journal of lightwave technology Vol. 37; no. 18; pp. 4501 - 4506
• Main Authors: Janik, Monika, Eftimov, Tinko, Koba, Marcin, Smietana, Mateusz, Bock, Wojtek J.
• Format: Journal Article
• Language: English
• Published: New York IEEE 15-09-2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Cavity resonators; Couplings; Enlargement; Expansion; Fiber lasers; Fiber optics sensors; Holes; interferometry; Laser machining; laser materials processing; Lasers; Mach-Zehnder interferometers; Microcavities; Micromachining; microstructure fabrication; Optical fiber sensors; Optical fibers; Refractivity; Sensitivity; Spectral sensitivity
• DOI: 10.1109/JLT.2019.2907661
• EISSN: 1558-2213
• ISSN: 0733-8724

This paper presents a theoretical analysis and experimental verification of fine-tuning of the spectral response and refractive index sensitivity of microcavity in-line Mach-Zehnder interferometer (µIMZI). The µIMZIs were fabricated using femtosecond (fs) laser micromachining in standard single-mode fibers as circular cavities with a diameter of 60 μ m. Next, the structures underwent fs laser postprocessing, which included fabrication of an additional cavity with the same diameter but shifted by 15 μ m or 30 μ m against the center of the initial microcavity. Different depths of the additional structures were investigated. The enlargement of the microcavity allows for tailoring the spectral response, i.e., it shifts the interference pattern by more than 200 nm, with no introduction of any additional losses and distortions in the spectrum. As the additional effect, regardless of the size of the extension, the sensitivity of the enlarged µIMZI was improved by 32%.