Tuning refractive index sensing properties of micro-cavity in-line Mach-Zehnder interferometer with plasma etching

This work presents an application of reactive ion etching (RIE) for an effective tuning of the spectral response and the refractive-index (RI) sensitivity of the micro-cavity in-line Mach-Zehnder interferometer (μIMZI). The μIMZIs were fabricated using femtosecond laser micromachining in a standard single-mode fiber as a form circular holes with a diameter of 54 μm. The application of RIE with SF6 and O2 used as reactive gas allows for an efficient and well-controlled etching of the fabricated structure. The process resulted in cleaning the bottom of the micro-cavity and smoothening of its sidewalls. In transmission measurements, the effect of the plasma processing was observed as an increase in both spectral depths of the minima and RI sensitivity of the structure, as well as improved wettability of the micro-cavity surface, which made the measurements faster and easier.

[1]  Y. Tzeng,et al.  Dry Etching of Silicon Materials in SF6 Based Plasmas. Roles of N2O and O2 Gas Additives. , 1987 .

[2]  W. J. Bock,et al.  Refractive-Index Sensing With Inline Core-Cladding Intermodal Interferometer Based on Silicon Nitride Nano-Coated Photonic Crystal Fiber , 2012, Journal of Lightwave Technology.

[3]  J M Baptista,et al.  All Fiber Mach–Zehnder Interferometer Based on Suspended Twin-Core Fiber , 2010, IEEE Photonics Technology Letters.

[4]  Wojtek J. Bock,et al.  Effect of Wet Etching of Arc-Induced Long-Period Gratings on Their Refractive Index Sensitivity , 2013 .

[5]  Wojtek J. Bock,et al.  Combined Plasma-Based Fiber Etching and Diamond-Like Carbon Nanooverlay Deposition for Enhancing Sensitivity of Long-Period Gratings , 2016, Journal of Lightwave Technology.

[6]  Wojtek J. Bock,et al.  Enhancing sensitivity of long-period gratings by combined fiber etching and diamond-like carbon nano-overlay deposition , 2015, International Conference on Optical Fibre Sensors.

[7]  Sumei Wang,et al.  Femtosecond laser fabricated all-optical fiber sensors with ultrahigh refractive index sensitivity: modeling and experiment. , 2011, Optics express.

[8]  Xiaoyan Sun,et al.  Highly sensitive refractive index fiber inline Mach–Zehnder interferometer fabricated by femtosecond laser micromachining and chemical etching , 2016 .

[9]  Wojtek J. Bock,et al.  Increased sensitivity of femtosecond laser micro-machined in-fiber Mach-Zehnder interferometer for small-scale refractive index sensing , 2016, European Workshop on Optical Fibre Sensors.

[10]  Predrag Mikulic,et al.  Measurements of reactive ion etching process effect using long-period fiber gratings. , 2014, Optics express.

[11]  Wojtek J. Bock,et al.  Tuning properties of long-period gratings by plasma post-processing of their diamond-like carbon nano-overlays , 2014 .

[12]  Youngjoo Chung,et al.  High temperature fiber sensor with high sensitivity based on core diameter mismatch. , 2008, Optics express.

[13]  C. Liao,et al.  Miniaturized fiber in-line Mach-Zehnder interferometer based on inner air cavity for high-temperature sensing. , 2012, Optics letters.

[14]  Y. Tzeng,et al.  Dry Etching of Silicon Materials in SF 6 Based Plasmas Roles of and Gas Additives , 1987 .

[15]  C. J. Mogab,et al.  Plasma etching of Si and SiO2—The effect of oxygen additions to CF4 plasmas , 1978 .