Abstract

Multi-wave mixing has been extensively studied in semiconductor optical amplifiers and more recently attention has been given to the use of cavity-enhanced mixing effects in laser diodes. In the present paper a report is given of calculations performed using a numerical model of nearly degenerate multiwave mixing in above-threshold laser diodes taking account of longitudinal variations in the nonlinear interactions.¹ The work is directed at optimising phase conjugate signal generation in laser diode structures. Effort has been given to establishing the opportunities for enhanced phased conjugation (in both reflection and transmission modes) using asymmetric laser diodes, i.e., those having unequal facet mirror reflectivities. In such structures significant longitudinal variations can arise in the probe-induced carrier density deviations in the laser structure. The importance of taking into account such variations in calculating phase conjugate signals has been demonstrated.^1-3 Having established the role of longitudinal gain variations in the multiwave mixing process it is of interest to consider semiconductor laser structures where such variations can be controlled by current injection. The simplest structure which can be considered in this context is the twin-section laser diodes shown schematically in Figure 1 with mirror reflectivities R₁ and R₂ and biasing currents J_a and J_b. The values of latter are given normalized to the transparency current. It is found that, under appropriate biasing conditions, such a device exhibits a uniform phase conjugate reflectivity over a frequency detiming range of more than 10 GHz.

© 1995 IEEE