DERIVATION OF A WAVE-EQUATION FOR PULSE-PROPAGATION BEYOND A SLOWLY VARYING ENVELOPE APPROXIMATION

An iterative method is used to derive an accurate wave equation that g overns ultrashort pulse propagation in a single mode fibre. In the der ivation, the slowly varying envelope approximation (SVEA) is not requi red. Therefore, the wave equation can be used to describe the propagat ion of an ultrashort pulse of a few optical cycles. It is found that, compared with the wave equation obtained by making an SVEA, an accurat e wave equation has the same coefficients of the linear dispersion ter ms and different coefficients of the high-order time derivatives of th e non-linear terms.