Coupling coefficients and propagation constants in guided wave distributed−feedback lasers

Abstract

Coupling coefficients and propagation constants in guided−wave distributed−feedback lasers are calculated. It is shown that higher−order transverse modes often have substantially larger coupling coefficients than do low−order transverse modes. Thus, higher−order modes require lower net gains at threshold. Grating spacings which resonate these higher−order modes are calculated and shown to differ significantly from the values appropriate to low−order modes. Higher−order modes also resonate at greater frequency separations, thus facilitating single−mode operation.