Transition between bulk and surface refractive index sensitivity of micro-cavity in-line Mach-Zehnder interferometer induced by thin film deposition.

In this work we discuss the refractive index (RI) sensitivity of a micro-cavity in-line Mach-Zehnder interferometer in the form of a cylindrical hole (40-50 μm in diameter) fabricated in a standard single-mode optical fiber using a femtosecond laser. The surface of the micro-cavity was coated with up to 400 nm aluminum oxide thin film using the atomic layer deposition method. Next, the film was progressively chemically etched and the influence on changes in the RI of liquid in the micro-cavity was determined at different stages of the experiment, i.e., at different thicknesses of the film. An effect of transition between sensitivity to the film thickness (surface) and the RI of liquid in the cavity (bulk) is demonstrated for the first time. We have found that depending on the interferometer working conditions determined by thin film properties, the device can be used for investigation of phenomena taking place at the surface, such as in case of specific label-free biosensing applications, or for small-volume RI analysis as required in analytical chemistry.

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

[2]  Sangwoo Lim,et al.  Etch Behavior of ALD Al2O3 on HfSiO and HfSiON Stacks in Acidic and Basic Etchants , 2011 .

[3]  Y. C. Lee,et al.  Al2O3 and TiO2 atomic layer deposition on copper for water corrosion resistance. , 2011, ACS applied materials & interfaces.

[4]  Predrag Mikulic,et al.  Capability for Fine Tuning of the Refractive Index Sensing Properties of Long-Period Gratings by Atomic Layer Deposited Al2O3 Overlays , 2013, Sensors.

[5]  Jacques Albert,et al.  Improved detection limits of protein optical fiber biosensors coated with gold nanoparticles. , 2014, Biosensors & bioelectronics.

[6]  Koji Sugioka,et al.  Femtosecond Laser Fabrication of Monolithically Integrated Microfluidic Sensors in Glass , 2014, Sensors.

[7]  Wojtek J. Bock,et al.  Recognition of bacterial lipopolysaccharide using bacteriophage-adhesin-coated long-period gratings. , 2015, Biosensors & bioelectronics.

[8]  Predrag Mikulic,et al.  Label-free sensitivity of long-period gratings enhanced by atomic layer deposited TiO(2) nano-overlays. , 2015, Optics express.

[9]  Gabriela Kuncová,et al.  Fiber-Optic Chemical Sensors and Fiber-Optic Bio-Sensors , 2015, Sensors.

[10]  Atsushi Seki,et al.  Efficient deep-hole drilling by a femtosecond, 400 nm second harmonic Ti:Sapphire laser for a fiber optic in-line/pico-liter spectrometer , 2015 .

[11]  M. Koba,et al.  Stack of Nano-Films on Optical Fiber End Face for Label-Free Bio-Recognition , 2016, Journal of Lightwave Technology.

[12]  Predrag Mikulic,et al.  Towards refractive index sensitivity of long-period gratings at level of tens of µm per refractive index unit: fiber cladding etching and nano-coating deposition. , 2016, Optics express.

[13]  S. Górska,et al.  Bacteriophage Adhesin-Coated Long-Period Grating-Based Sensor: Bacteria Detection Specificity , 2016, Journal of Lightwave Technology.

[14]  W. Bock,et al.  Sensitivity Pattern of Femtosecond Laser Micromachined and Plasma-Processed In-Fiber Mach-Zehnder Interferometers, as Applied to Small-Scale Refractive Index Sensing , 2017, IEEE Sensors Journal.

[15]  M. Godlewski,et al.  Titanium oxide thin films obtained with physical and chemical vapour deposition methods for optical biosensing purposes. , 2017, Biosensors & bioelectronics.

[16]  Gang-Ding Peng,et al.  Label-free detection of bovine serum albumin based on an in-fiber Mach-Zehnder interferometric biosensor. , 2017, Optics express.