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The group index for TE modes in an asymmetrical slab waveguide is investigated, and a simple analytical expression is derived. It is shown that the product of the phase and group indices is related to the power fraction in each of the three layers of the waveguide. The results are of interest in the analysis of double heterostructure semiconductor… (More)
An analysis of the threshold current for double-heterostructure GaInAsP lasers is presented. The analysis is based on a simple expression for the gain-current relation and includes the effect of optical confinement. Using a refractive- index model for GaInAsP compounds, lasers emitting at 1.55 microm are investigated. Asymmetrical structures, i.e., lasers… (More)
Buried heterostructure lasers are analyzed in terms of modegain using the effective index method. Useful combinations of active region width and composition of the bounding layers are found by requiring low threshold current density, fundamental mode operation, and allowing a 10% tolerance on the active layer thickness.
A computer programme is described which can undertake automatic distribution of patients referred for elective surgery. The programme ensures coordinated reservation of operation and bed resources. The programme provides copies of admission and operation lists to the departments concerned and, similarly, it writes out distribution lists and summoning… (More)