| 3D vectorial modelling of photonic waveguide microresonators | ||
| Prof. Jiří Čtyroký, DSc.; Ladislav Prkna, MSc.; Milan Hubálek, MSc. | ||
| Year: 2004 | ||
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Photonic waveguide microresonators are very promising building blocks
for photonic large-scale integrated devices combining functions like
spectral filtering, add/drop wavelength-division multiplexing (WDM),
space switching, modulation, etc., with expected extensive
applications in metropolitan and access photonic networks. The basic
idea can be understood from the left figure below. Waveguide ring
microresonators coupled by evanescent coupling (optical tunelling) to
straight waveguides. The way where the optical signal goes depends on
its wavelength: if the ring microresonator is off resonance, the
signal is only weakly affected by the presence of a microresonator and
exits from the “through” port, while at resonance it appears at the
“drop” port. As the resonance wavelength of a microresonator can be
changed electrooptically, thermooptically or using optical (Kerr-type)
nonlinearity, such a device can be used not only as a passive spectral
filter or add/drop WDM multiplexor but also as a tunable filter, as a
modulator, or even as an optical logical element. In order to keep
both the size and radiation loss of the microresonators small (typical
diameter of the ring microresonator varies from a few micrometers to
hundreds of micrometers), high-refractive index contrast waveguides
have to be used. For the design of such structures, a 3D vectorial
modelling of optical field distribution in the microresonators is
necessary.
We have developed a novel semianalytic method for accurate and efficient calculation of vectorial electromagnetic field distribution in circular microresonators on a standard PC computer. The method is based on mode matching and is especially suitable for accurate calculation of radiation losses in both ring and disk microresonators. The right figure shows as an example the distribution of the dominant (vertical) electric field component of the fundamental TM eigenmode of the disk microresonator. The field discontinuity at horizontal interfaces and radiation into substrate in the right down direction are clearly visible. The method has been developed within European project IST-2000-28018 „NAIS“, and in combination with the coupled-mode theory developed at the University of Twente in the Netherlands it forms an original and efficient tool for modelling and design photonic microresonator devices. |
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