Self-pulsating laser diode and a method for causing a laser diode to output light pulses

Abstract

A semiconductor self-pulsating laser diode ( ) comprises a wave guiding layer ( ) sandwiched between lower and upper cladding layers ( ). A current blocking layer ( ) defining a slot ( ) through which pumping current is directed through the laser diode between upper and lower contact plates ( ) defines an active wave guiding region ( ). The current blocking layer ( ) is shaped by the formation of longitudinally extending recesses ( ) for defining the active wave guiding region ( ) such that a central pulse light generating region ( ) is formed surrounded by an outer light propagating region ( ). As the laser diode is continuously pumped, an effective step change in refractive index between the wave guiding layer ( ) and the outer light propagating region ( ) is formed, and the carrier density and refractive index profiles across the active wave guiding region ( ) vary as each light pulse cycle progresses. Initially, the carrier density in the central pulse light generating region rises relative to the carrier density in the light propagating region until the difference between the refractive index of the pulse light generating region and the refractive index of the light propagating region is at its greatest, and the carrier density of the pulse light generating region reaches its lasing threshold value. At this stage lasing commences in the active wave guiding region . Lasing in the pulse light generating region progressively reduces the carrier density therein, which in turn progressively reduces the relative difference between the refractive index of the pulse light generating region and the light propagating region until the refractive index of the pulse light generating region approaches the refractive index of the light propagating region , thereby increasing guiding of lasing light into the pulse light generating region for emission of the light pulse therefrom. At that stage the carrier density of the active wave guiding region falls below its lasing threshold value, thus extinguishing the lasing light, and the next light pulse cycle commences.