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Exactness of simplified scalar optical approaches in modelling a threshold operation of possible nitride vertical‐cavity surface‐emitting diode lasers

Modern small‐size vertical‐cavity surface‐emitting diode lasers (VCSELs) require principally fully vectorial optical modelling because their cavity sizes are of the order of the wavelength of emitted radiation. However, much simpler scalar approaches are often surprisingly exact even beyond the limits of their confirmed validity. Therefore, in the present paper, reasonable limits of an application of simplified scalar optical approaches (instead of more exact but also much more involved and time‐consuming rigorous vectorial ones) are determined to model threshold operation of possible nitride VCSELs equipped with tunnel junctions with the aid of a comparison of results of the scalar effective frequency method with those obtained using the fully vectorial three‐dimensional plane wave admittance method. Both these optical methods have been found to give usually quite close results for the fundamental transverse mode. Larger discrepancies between the results of both approaches have been found for first‐order transverse modes (and even larger are expected for higher‐order ones) and for larger (or very small) active regions. Some structural modifications of nitride VCSELs, which may enable their low‐threshold single‐fundamental‐mode room‐temperature continuous‐wave operation, are proposed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)