Abstract

There has been considerable interest in bistable optical devices which can be used to perform optical switching, signal processing and act as optically controlled memory elements and light sources. One method of achieving optical bistability combines a medium which displays nonlinear optical gain with inhomogeneous current injection resulting in saturable absorbers.¹⁻³ Electrical input signals are commonly used for controlling the switching, but it was also shown to be effective with longitudinal light injection with such a device.⁴ We report here for the first time the use of transverse light injection, i.e. perpendicular to the plane of the active layer, to switch from OFF to ON state. Figure 1(a) illustrates the structure of the interdigitated contact semiconductor laser. There are two independent contacts. Each contact is made up of many fingers which form an interlocking come-like structure. Each gain region can be considered as a rectangle of width W and length L_g where current is injected as shown in Fig. 1(b). Between the fingers are absorber regions of dimensions W by L_g. W is defined by the striped width while L_g1 and are defined by the widths of the fingers. When both sets of fingers are pumped, the absorber region is limited to the unpumped region. When only either set of fingers is pumped, then the absorber region length is increased by the width of the finger where current pumping is not activated. Thus if the dimension L_g1 is different from L_g2, then 3 different absorber region lengths can be activated. The regions not covered by the fingers allow light to be injected.

© 1995 IEEE