Hochgüte - Mikrowellenresonatoren mit photonischer Kristallstruktur
Hochgüte - Mikrowellenresonatoren mit photonischer Kristallstruktur
A photonic crystal is an artificially machined material with a spatially periodic dielectricconstant. The eigenfrequencies of the solutions of a wave equation for electromagnetic wavespropagating in this type of medium are arranged in bands and band gaps: It can be shown thata propagation inside the...
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Personal Name(s): | Schuster, Michael (Corresponding author) |
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Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2001
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Physical Description: |
99 p. |
Document Type: |
Report Book |
Research Program: |
ohne Topic |
Series Title: |
Berichte des Forschungszentrums Jülich
3901 |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
A photonic crystal is an artificially machined material with a spatially periodic dielectricconstant. The eigenfrequencies of the solutions of a wave equation for electromagnetic wavespropagating in this type of medium are arranged in bands and band gaps: It can be shown thata propagation inside the photonic crystal is not possible for waves with frequencies out ofcertain bands. Those forbidden bands are called photonic band gaps (PBG).When dielectric material is added or removed, the perfect periodicity is broken, and a defectmode with a frequency in the band gap can exist locally. Its electromagnetic field concentratesin the defect area and decays exponentially into the surrounding photonic crystal.The possible field for photonic crystal applications extends from the microwave range up tothe optical frequency range. In the microwave field several possible applications have beendemonstrated, for example waveguides, beam splitters and high directivity antenna arrays.The localisation of electromagnetic energy at a defect in a photonic crystal is similar to a wellknown effect employed to construct high-Q microwave resonators: In a Whispering Gallery(WHG-) mode resonator the high Q-factor is achieved by localisation of the electromagneticfield energy by total reflection inside a disk made of dielectric material.The topic of this work is to demonstrate, that WHG-like modes can exist in an air defect in aphotonic crystal that extends over several lattice periods; and that a high-Q microwaveresonator can be made, utilizing these resonant modes.In numerical simulations, the transmission properties of a photonic crystal structure withhexagonal lattice symmetry have been investigated with a transfer-matrix-method. Theeigenmodes of a defect structure in a photonic crystal have been calculated with a quasi-3dfinite element integration technique.Experimental results confirm the simulated transmission properties and show the existence ofmodes inside the band gap, when a defect is introduced in the crystal. Resonatormeasurements show that a microwave resonator can be operated with those defect modes.lt was found out that the main losses of the resonator were caused by bad microwaveproperties of the used dielectric material and by metal losses an the top and bottom resonatorWalls. Furthermore, it turned out that the detection of the photonic crystal defect mode wasdifficult because of a lack of simulation possibilities and high housing mode density in theresonator.A perspective for resonator improvement is the use of other low loss microwave dielectricslike sapphire and the employment of different machining tools. Additionally, modeconfinement by the photonic crystal can be improved by using a 3dimensional photoniccrystal, like the woodpile structure, made of sapphire rods. |