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Development of Fiber Optic Sensors using Femtosecond Laser for Refractive Index and Temperature Measurements

The development and transition of optical fiber sensors from experimental stage to practical applications largely depends on manufacturing cost and simplicity. To date, in-fiber grating sensors are largely manufactured by ultraviolet lasers despite higher fabrication cost and complexity. Besides, ultraviolet radiation can only write gratings in doped fibers. Therefore, reaping the benefits of existing fibers such as pure silica fiber, photonics crystal fibers etc. cannot be achieved using this technique. In contrast, uses of ultra-fast lasers have the potential to eliminate or minimize those drawbacks. However, extensive fabrication and packaging research is required for ultrafast laser technology to mature and offer grating based sensors fabrication in industrial scale.

This dissertation presents design and fabrication of fiber optic sensors using femtosecond laser for measurement of ambient refractive index and temperature. The femtosecond laser operating at 780 nm with pulse duration of 172 fs and pulse repetition rate of 1 kHz is used to study bulk index modification and fabricate fiber long period and short period gratings. Effective and reliable fabrication of in-fiber gratings requires spatial control of refractive index written in optical fiber. With an aim to better control spatial index modulation in direct ultrafast writing, primary focus of this work is given to write single-shot submicron periodic voids in bulk glass. Femtosecond pulse filamentation in glass is studied to understand the morphology of bulk index change written by ultrashort pulses. Laser writing parameters (such as beam diameter, pulse energy, scanning speed, depth of focus, etc.) are then further tuned to write pulse filamentation induced refractive index change in optical fibers suitable for fiber grating fabrication. In order to design and tailor grating’s spectrum, measurement of in-fiber index is introduced in this work. We propose fiber Bragg grating based Fabry-Perot cavity structure (cavity length, L= 10 mm) to characterize femtosecond pulse filamentation induced refractive index change in the core of standard SMF. In addition, Mach-Zehnder interferometer (MZI) is proposed as an alternative yet effective and low cost tool to measure in-fiber index change. Comsol simulation is used to validate the quantification of index change. Measured index change is used in Optiwave simulation to design fiber long period gratings in standard telecommunication and pure silica core fibers. To increase fabrication reliability, we introduce inscription of helical long period gratings using a custom made rotary stage. Tapered photonic crystal and microfiber based Mach-Zehnder interferometer is also investigated for ambient refractive index measurement. Miniature fiber Bragg grating written in microfiber Mach-Zehnder interferometer is used in this work for multi-parameter sensing as well as temperature compensated refractive index sensing. Microfiber Bragg gratings buried in materials of higher thermal expansion coefficient is also proposed to significantly enhance temperature sensitivity. / Graduate / 0548, 0794, 0775 / fariduvic@gmail.com

  1. http://hdl.handle.net/1828/6995
  2. Farid Ahmed and Martin B.G. Jun “Microfiber Bragg Grating Sandwiched between Standard Optical Fibers for Enhanced Temperature Sensing,” Photon. Technol. Lett. DOI:10.1109/LPT.2015.2504564, 2015.
  3. Farid Ahmed, Hang-Eun Joe, Byung-Kwon Min, and Martin B.G. Jun ,”Characterization of Refractive Index Change and Fabrication of Long Period Gratings in Pure Silica Fiber by Femtosecond Laser Radiation,” Optic and laser Technology, 74, 119–124, 2015.
  4. Md. Shamim Ahsan, Man Seop Lee, Mohammad Khairul Hasan, Young-Chul Noh, Ik-Bu Sohn, Farid Ahmed, Martin B.G. Jun, “Formation mechanism of self-organized nano-ripples on quartz surface using femtosecond laser pulses,” Optik – Int. Journal for Light and Electron Optics, 126 (24), pp. 5979-5983, 2015.
  5. Farid Ahmed, and Martin Jun, “Filament-based fabrication and performance analysis of fiber Bragg grating sensors using ultrashort pulse laser,” J. Micro Nano-Manuf. 2(2), 021007, 2014.
  6. Farid Ahmed, M. Shamim Ahsan, ManSeop Lee, Martin Jun, “Near-field modification of femtosecond laser beam to enhance single-shot pulse filamentation in glass medium,”Appl. Phys. A, 114, P 1161- 1165, 2014.
  7. Levi Smith, Farid Ahmed, Afshin Jooshesh, Jinye Zhang, Martin Jun, Thomas Darcie “THz Field Enhancement by Antenna Coupling to a Tapered Thick Slot Waveguide,” Journal of Lightwave Technology vol. 32(20), pp. 3676-3682, 2014.
  8. Sukhwinder Bhullar, Farid Ahmed, Junghyuk Ko and Maring Byung-Guk Jun, “Design and fabrication of stent with negative Poisson’s ratio,” International Journal of Mechanical, Industrial Science and Engineering, 8(2), pp. 2538-2544, 2014.
  9. Junghyuk Ko, Nima Khadem Mohtaram, Farid Ahmed, Amy Montgomery, Michael Carlson, Patrick C.D. Lee, Stephanie M. Willerth, Martin B.G. Jun “Fabrication of poly (ε-caprolactone) microfibers scaffolds with varying topography and mechanical properties for stem cell-based tissue engineering application,” Journal of Biomaterials Science Polymer Edition, 25(1), pp. 1-17, 2014.
  10. Junghyuk Ko, Kathleen Kolehmainen, Farid Ahmed, Martin B.G. Jun, Stephanie M. Willerth “Towards high throughput tissue engineering: development of chitosan-calcium phosphate scaffolds for engineering bone tissue from embryonic stem cell,” Am J Stem Cell, Vol.1(1), pp 81-89, 2012.
  11. Md. Shamim Ahsan, Farid Ahmed, Yeong Gyu Kim, Man Seop Lee, Martin B. G. Jun, “Colorizing stainless steel surface by femtosecond laser induced micro/nano-structures,” Appl. Surface Science 257 (17), P 7771-7777 2011.
Identiferoai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/6995
Date24 December 2015
CreatorsAhmed, Farid
ContributorsJun, Martin
Source SetsUniversity of Victoria
LanguageEnglish, English
Detected LanguageEnglish
TypeThesis
Formatapplication/pdf
RightsAvailable to the World Wide Web

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