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.
Aalto

High-Accuracy Characterization of Optical Components: Detectors, Coatings and Fibers

Antti Lamminpää

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 Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 1st of December, 2006, at 12 noon.

Overview in PDF format (ISBN 951-22-8481-2)   [2051 KB]
Dissertation is also available in print (ISBN 951-22-8480-4)

Abstract

The work described in this thesis is concentrating on the high-accuracy characterization of optical components.

Two trap detectors utilizing germanium and GaAsP photodiodes are constructed and characterized. The results for germanium detectors show that trap detector is well-suitable for applications where harmful inter-reflections need to be avoided. Furthermore, the spatial uniformities of the germanium photodiodes have improved significantly during the recent years. However, germanium detectors have relatively low shunt resistance, which needs to be taken into account when high-accuracy measurements are carried out. Unlike silicon detectors, the GaAsP detectors offer smooth spectral responsivity in the ultraviolet wavelength region and solar blindness. In addition the trap configuration approximately doubles, otherwise relatively low, spectral responsivity of the GaAsP photodiodes. The responsivity of both studied trap detectors is traceable to the cryogenic radiometer making them suitable for absolute power calibrations.

The reliability of the optical characterization methods relies strongly on the accuracy and properties of the applied detectors. High precision spectrophotometric measurements performed at various oblique angles of incidence can improve the determination of optical parameters of thin films. However, this requires systematic error factors such as misalignment in polarization plane and incidence angle and quality of beam collimation to be taken into account. The spectral reflectance and transmittance measurements are carried out for incidence angles varying between normal and Brewster's angle and the results are compared. For the first time, the reached consistency of ∼ 0.2 % between the results confirms the accuracy of the spectrophotometric characterization technique.

The determination of nonlinearity of optical fibers has become more important as the transmission lengths and used optical power has increased in optical long-haul networks. In the thesis, two major improvements for the continuous-wave self-phase modulation method for the determination of nonlinear coefficient of optical fibers have been demonstrated. The first one is a technique to take the effects of dispersion into account by using mathematical modeling based on the Nonlinear Schrödinger Equation. Another one is a measurement scheme of high fiber optic power based on the integrating sphere detector. Together these improvements reduce the uncertainty in the determination of nonlinear coefficient to the level of 2.0 % (k = 2).

This thesis consists of an overview and of the following 5 publications:

  1. A. Lamminpää, M. Noorma, T. Hyyppä, F. Manoocheri, P. Kärhä and E. Ikonen, Characterization of germanium photodiodes and trap detector, Measurement Science and Technology 17, 908-912 (2006). © 2006 Institute of Physics Publishing. By permission.
  2. M. Noorma, P. Kärhä, A. Lamminpää, S. Nevas and E. Ikonen, Characterization of GaAsP trap detector for radiometric measurements in ultraviolet wavelength region, Review of Scientific Instruments 76, 033110 (2005). © 2005 American Institute of Physics. By permission.
  3. A. Lamminpää, S. Nevas, F. Manoocheri and E. Ikonen, Characterization of thin films based on reflectance and transmittance measurements at oblique angles of incidence, Applied Optics 45, 1392-1396 (2006). © 2006 Optical Society of America (OSA). By permission.
  4. A. Lamminpää, T. Niemi, E. Ikonen, P. Marttila and H. Ludvigsen, Effects of dispersion on nonlinearity measurement of optical fibers, Optical Fiber Technology 11, 278-285 (2005).
  5. A. Lamminpää, T. Hieta, J. Envall and E. Ikonen, Reliable determination of optical fiber nonlinearity using dispersion simulations and improved power measurements, Journal of Lightwave Technology, accepted for publication (2006). © 2006 IEEE. By permission.

Keywords: measurement standard, thin films, spectrophotometry, nonlinear fiber optics, ultraviolet, infrared

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© 2006 Helsinki University of Technology

Last update 2011-05-26