Refractive index sensing with Al2O3-nanocoated long-period gratings working at dispersion turning point: Temperature cross-sensitivity

In this work is discussed an effect of nanocoating long-period grating (LPG) with an aluminum oxide (Al2O3) on its refractive index (RI) and temperature (T) sensitivity. For comparison two LPGs, namely one before and after the nanocoating process were optimized towards working at dispersion turning point (DTP) of higher order cladding modes. The DTP was reached with two methods, i.e., by wet etching of LPG's cladding and by optimized deposition of Al2O3 thin overlay using atomic layer deposition (ALD) method. For both the cases we show significant increase in RI sensitivity at DTP. When Al2O3 is deposited the RI sensitivity reaches 9270 nm/RIU for traced only one resonance out of the pair and RI in range 1.33–1.34 RIU, what is over 4-fold higher than for the bare LPG. Moreover, T sensitivity for both the structures was compared and the one for Al2O3-coated sample was found to be only up to 12% higher than for the bare sample. Higher RI sensitivity and low temperature cross-sensitivity effects allow for more accurate RI measurements than in case of bare LPGs. The Al2O3-nanocoated LPGs can further find applications in label-free biosensing, due to their optimized sensitivity in RI in range close that of water.

[1]  V. Bhatia.  Applications of long-period gratings to single and multi-parameter sensing. , 1999, Optics express.

[2]  Wojtek J. Bock,et al.  Detection of bacteria using bacteriophages as recognition elements immobilized on long-period fiber gratings. , 2011, Optics express.

[3]  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.

[4]  Wojtek J. Bock,et al.  Temperature sensitivity of silicon nitride nanocoated long-period gratings working in various surrounding media , 2011 .

[5]  W. J. Bock,et al.  Tuned Pressure Sensitivity of Dual Resonant Long-Period Gratings Written in Boron Co-Doped Optical Fiber , 2012, Journal of Lightwave Technology.

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

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

[9]  S. James,et al.  Modification of the refractive index response of long period gratings using thin film overlays , 2005 .

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

[11]  John E. Sipe,et al.  Long-period fiber gratings as band-rejection filters , 1995 .

[12]  Ping Miao,et al.  Sensitivity characteristics of long-period fiber gratings , 2005, SPIE/OSA/IEEE Asia Communications and Photonics.

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

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

[15]  Ashish M. Vengsarkar.  Long period fiber gratings , 1996, Optical Fiber Communications, OFC..

[16]  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.

[17]  Mateusz Śmietana,et al.  Label-free Gram-negative bacteria detection using bacteriophage-adhesin-coated long-period gratings. , 2016, Biomedical optics express.