Optoelectronic integrated tristable device with optically controlled set and reset functions

An optical tristable device with optically controlled set and reset functions is developed. The device structure is a vertical and direct integration of four heterojunction phototransistors (HPTs) and a laser diode (LD). Two HPTS (HPT-A and HPT-B) integrated just above the LD stripe are utilized to achieve the set operation. The internal optical feedback from the LD to the HPTs takes an important role in the operation. On the other hand, another HPT (HPT-C or HPT-D) integrated slightly away from the position for the set operation is used to achieve the reset operation. The optical feedback from the LD to the HPT-A and HPT-B is suppressed by the current bypass through the HPT-C connected to both ends of the LD. Theoretical calculations are also made to explain these operations