A finite thickness slab of two-dimensional photonic band-gap (PBG) material is analyzed to determine the plane-waue reflection and transmission coefficients as functions of the angle of incidence. It is shown that within the band-gap, where there is total reflection, the reflection is equivalent to that from a plane surface located within the PBG material (the reflection plane concept). The two-dimensional PBG material is used as an all-dielectic reflector for an electric dipole antenna. Fidd patterns computed with the use of the rejlection plane concept are compared with measurements made on an experimental model and are found to be in good agreement. A three-dimensional PBG material with a BCC lattice is also used as a reflector for an electric dipole antenna. Field patterns calculated for this structure using the finite-differencetime-domain (FDTD) method are also in good agreement with measurements.
Ultrafast gain dynamics in GaAlAs diode amplifiers have been studied using 100 fs optical pulses. Pulse propagation through the amplifier resulted in temporal broadening and pulse shaping due to both gain saturation and material dispersion. Pump-probe experiments indicate the presence of two processes contributing to the gain dynamics but give no evidence of spectral hole burning. A dynamic carrier heating model is presented to explain all of the observed gain nonlinearities, and the implications of our results on the dynamic response of laser diodes are discussed.
We present results of pump-probe experiments on GaAlAs laser diodes indicating a 0.9-ps relaxation time associated with the device transmission. Subpicosecond, tunable near infrared pulses obtained by fiber compression were used to carry out the experiments. The data strongly support a model in which a nonequilibrium carrier temperature in the active layer is responsible for the observed signal.
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