Browsing by Subject "Fabry-Perot Cavity"

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    Characterization of photonic crystals at microwave frequencies
    (1996) Temelkuran, Burak
    VVe investigated the surface reflection properties of layer-by-layer photonic crystals, for dielectric and metallic based photonic crystals. By using a FabryPerot cavity analogy with the reflection-phase information of the photonic crystals, we predicted defect frequencies of planar defect structures. Our predictions were in good agreement with the measured defect frequencies. The Fabry-Perot cavity analogy was also used to relate the quality factors of the planar defect structures to the transmission of the mirrors of the cavity. A simple model was used to simulate the transmission spectra of planar defect structures, which agreed well with the experimental data. We also investigated the transmission and reflection properties of two different metallic crystal structures (face-centeredtetragonal and simple tetragonal). We obtained rejection rates of 7-8 dB per layer from metallic crystals. Defect modes created by removing rods resulted in high peak transmission (80%), and high quality factors (1740). Our measurements were in good agreement with theoretical simulations of metallic structures. Planar defect structures built around metallic structures resulted in higher quality factors (2250). We observed high reflection-rejection ratios (-80 dB) at defect frequencies for planar defect structures, which was explained by using the Fabry-Perot analogy. Finally, the enhanced field inside the defect volume was measured, by using a monopole receiver antenna inserted inside the defect. The maximum observed enhancement with respect to the incident field was around 200 for a planar defect structure. By placing a Schottky diode detector inside planar and box-like defects, we built resonant cavity enhanced (RCE) detectors and measured the enhanced field inside the defect.
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    Fabrication and characterization of high speed resonant cavity enhanced Schottky photodiodes
    (1996) Islam, M. Saiful
    High speed, high external quantum efficiency and narrow spectral linewidth make resonant cavity enhanced (RC E) Schottky photodetector a good candidate for telecommunication applications. In this thesis, we present our work for the design, fabrication and characterization of a RCE Schottky photodiode with high quantum efficiency and high speed. We present experimental results on a RCE photodiode having an operating wavelength of 900 nm. The absorption takes place in a thin InGaAs layer placed inside the GaAs cavity. The active region was grown above a highreflectivity GaAs/AIAs quarter-wavelength Bragg reflector. The top mirror consisted of a 200A thin Au layer which also acted as Schottky metal of the device. An external quantum efficiency of 55% was obtained from our devices. We demonstrate that the spectral response can be tailored by etching the top surface of the microcavity. Our high speed measurements yielded a FW HM of 30 ps, which is the record response for any RCE Schottky photodiode ever reported.
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    Physics and applications of coupled-cavity structures in photonic crystals
    (2002) Bayındır, Mehmet
    We proposed and demonstrated a new type of propagation mechanism for the electromagnetic waves in photonic band gap materials. Photons propagate through coupled cavities due to interaction between the highly localized neighboring cavity modes. We reported a novel waveguide, which we called coupled-cavity waveguide (CCW), in two- and three-dimensional photonic structures. By using CCWs, we demonstrated lossless and reflectionless waveguide bends, efficient power splitters, and photonic switches. We also experimentally observed the splitting of eigenmodes in coupled-cavities and formation of defect band due to interaction between the cavity modes. We reported the modification of spontaneous emission from hydrogenated amorphous silicon-nitride and silicon-oxide multilayers with coupled Fabry-Perot microcavities. We observed that the spontaneous emission rate is drastically enhanced at the coupledmicrocavity band edges due to very long photon lifetime. We also simulated our photonic structures by using the Transfer-Matrix-Method (TMM) and the Finite-Difference-Time-Domain (FDTD) method. The tight-binding (TB) approach, which was originally developped for the electronic structure calculations, is applied to the photonic structures, and compared to our experimental results. The measured results agree well with the simulations and the prediction of TB approximation. The excellent agreement between the measured, simulated, and the TB results is an indication of potential usage of TB approximation in photonic structures. Our achievements open up a new research area, namely physics and applications of coupled-cavities, in photonic structures. These results are very promising to construct for the future all-optical components on a single chip.