We studied enhancement and suppression of spontaneous emission in thin-film InGaAs/InP photonic crystals at room temperature. Angular resolved photoluminescence measurements were used to determine experimentally the band structure of conduction band of such a photonic crystal and overall enhancement of spontaneous emission. We demonstrated spontaneous emission enhancement in thin slab photonic crystals. It was shown that emission into the leaky conduction bands of the crystal has the same effect as cavity-enhanced spontaneous emission provided these bands are flat enough relative to the emission band of the material.
The Finite Difference Time Domain method has been used to analyze the dispersion diagram of a photonic crystal comprised of a perforated dielectric slab and the properties of a micro-cavity formed by introducing a defect into such a crystal. Computational requirements of the method, its advantages and disadvantages, and results for the structure analyzed are discussed.
A model of optical processes in LEDs was created that takes into account device geometry, light absorption in contacts and cladding layers, photon recycling, light randomization due to surface scattering and the benefit from encapsulation of the device into epoxy. Based on the results of our modeling, an optimization of the LED was proposed. Also, photoluminescence measurements of internal quantum efficiency were performed on the epi-layers used for LED fabrication.
We investigate high-power InGaAsP/GaAs (0.77 - 0.83 micrometers ) buried heterostructure lasers grown by LPE technique. A redistribution of the output power in the far field pattern from higher-order modes into the fundamental mode was observed with a temperature increase in the range of 10 degree(s) - 70 degree(s)C. A theoretical model taking into account the affect of boundary recombination velocity on the mesa walls on the carrier concentration profile in the active region is proposed. Significant rise of the boundary recombination velocity with temperature was confirmed experimentally by comparing the temperature dependences of quantum efficiency in buried and stripe-contact (without mesa walls) lasers fabricated from the same wafers. As a result of these investigations, we propose a new laser design in which the carrier concentration profile is similar to that in a heated device. A narrow contact mesa stripe laser permits us to concentrate most of the pumping current in the middle of active region and, hence, to increase the overlap of the carrier concentration profile with the fundamental mode intensity. The optimal dimensions for single-mode laser were calculated.
Conference Committee Involvement (1)
Optical Transmission, Switching, and Subsystems II