Heterostructure GaAs–AlxGa1−xAs–GaAs waveguides for 10.6 μm wavelength grown by liquid-phase epitaxy have a linear variation of dielectric constant in their substrates. On the basis of their mode equation, a computer program was devised for obtaining optimum values of the six parameters that define the index profiles, given a sufficient number and distribution of mode-angle measurements. The optimized parameters agreed well with the measured values for a variety of waveguides, illustrating the generality of the parameter-optimization procedure. Two types of leaky modes were observed, whose effective index β/k is less than the seed index, (1) Lummer–Gehrcke modes that are incompletely reflected at the substrate–seed interface and (2) low-loss totally reflected modes whose evanescent fields radiate into high-index seeds.
© 1975 Optical Society of AmericaFull Article | PDF Article
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