The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Novel Sensor and Telecommunication Applications of Photonic Crystal Fibers

Tuomo Ritari

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Micronova at Helsinki University of Technology (Espoo, Finland) on the 4th of August, 2006, at 12 noon.

Overview in PDF format (ISBN 951-22-8299-2)   [3386 KB]
Dissertation is also available in print (ISBN 951-22-8298-4)

Abstract

Photonic crystal fibers are novel optical waveguides containing a periodic array of air holes running along the fiber around a solid or hollow core. These fibers have recently attracted great interest in many research areas such as in nonlinear optics and measurement science as their manufacturing process allows for a high flexibility in the fiber design. Index-guiding photonic crystal fibers are commonly referred to as microstructured fibers whereas hollow-core photonic crystal fibers which guide light through a photonic bandgap effect are called photonic bandgap fibers. The thesis provides results on the polarization properties of microstructured fibers and presents novel applications which utilize both the unique physical structure and optical characteristics of microstructured and photonic bandgap fibers.

Polarization effects can have a great impact on the operation of fiber-based devices and communication systems. In particular, polarization-mode dispersion can limit long distance high bit-rate data transmission. In this thesis, the polarization characteristics of microstructured fibers and the sensitivity of these properties to the temperature and wavelength are studied. Also, polarization-mode dispersion of large mode-area microstructured fibers is investigated.

One of the earliest applications of microstructured fibers is supercontinuum generation. In the thesis, supercontinuum generation is studied in large mode-area microstructured fibers by employing nanosecond laser pulses. The special properties of these fibers allow for the realization of single-mode supercontinuum sources with a high spectral density, low output beam divergence and low polarization dependence. Moreover, a novel nanosecond supercontinuum source based on an acetylene-filled nonlinear microstructured fiber is presented. The approach provides a broadband source that is self-referenced to the absorption lines of the gas.

Air-guiding photonic bandgap fibers can guide more than 98% of the light in air thus reducing the influence of the material parameters of silica on the optical properties of the fiber. By filling the fiber holes with gas, such a fiber can provide a very long optical path length in compact fashion. In this thesis, the use of photonic bandgap fibers in gas sensing is studied. The high sensitivity and long interaction length provided by PBFs allows for the detection of molecules with weak absorption lines. In addition, a compact optical wavelength reference based on a gas-filled photonic bandgap fiber is presented. By utilizing lock-in technique, the output frequency of the laser was stabilized to the center point of weak acetylene absorption lines coinciding with wavelength division multiplexing channels.

This thesis consists of an overview and of the following 6 publications:

  1. T. Ritari, M. Wegmuller, M. Legré, N. Gisin, J. R. Folkenberg, M. D. Nielsen, and H. Ludvigsen, Experimental study of polarization properties of highly birefringent photonic crystal fibers, Optics Express 12, 5931-5939 (2004). © 2004 Optical Society of America (OSA). By permission.
  2. T. Ritari, T. Niemi, M. Wegmuller, N. Gisin, J. R. Folkenberg, A. Petterson, and H. Ludvigsen, Polarization-mode dispersion of large mode-area photonic crystal fibers, Optics Communications 226, 233-239 (2003). © 2003 Elsevier Science. By permission.
  3. G. Genty, T. Ritari, and H. Ludvigsen, Supercontinuum generation in large mode-area microstructured fibers, Optics Express 13, 8625-8633 (2005). © 2005 Optical Society of America (OSA). By permission.
  4. T. Ritari, G. Genty, and H. Ludvigsen, Supercontinuum and gas cell in a single microstructured fiber, Optics Letters 30, 3380-3382 (2005). © 2005 Optical Society of America (OSA). By permission.
  5. T. Ritari, J. Tuominen, J. C. Petersen, T. Sørensen, T. P. Hansen, H. R. Simonsen, and H. Ludvigsen, Gas sensing using air-guiding photonic bandgap fibers, Optics Express 12, 4080-4087 (2004). © 2004 Optical Society of America (OSA). By permission.
  6. J. Tuominen, T. Ritari, J. C. Petersen, and H. Ludvigsen, Gas filled photonic bandgap fibers as wavelength references, Optics Communications 255, 272-277 (2005). © 2005 Elsevier Science. By permission.

Keywords: photonic crystal fiber, polarization-mode dispersion, supercontinuum, gas detection, wavelength reference

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© 2006 Helsinki University of Technology

Last update 2011-05-26