Semiconductor diode laser having improved performance and method of

Abstract

Semiconductor diode lasers are used inter alia in optical disc systems, laser printers, bar code readers, and glass fibre communication systems. Lasers having a so-called (weakly) index-guided structure are very suitable for many applications inter alia because they can be manufactured comparatively simply and reliably. A disadvantage of the known (weakly) index-guided laser is that the so-called P-I (=optical power-current) characteristic thereof exhibits a kink. Such a kink limits the use of the laser to a relatively low optical power. According to the invention, such a (weakly) index-guided laser has a resonance cavity with a length for which the optical power at which a kink occurs in the P-I characteristic is a maximum. It was a surprise to find that the occurrence of a kink in the P-I curve of such a (weakly) index-guided laser depends on the length of the resonance cavity. Very surprising is the appearance of a maximum value in this kink power as a function of the length of the resonance cavity. Equally surprising is the occurrence of a series of such maxima, which are substantially equally high, and which are formed by the crests of a sawtooth curve with a very steep flank at the rising edge to each maximum. As a result, the laser length may be optimized not only in relation to the occurrence of kinks in the P-I characteristic but also in relation to other properties. The invention also relates to a method of manufacturing a laser according to the invention, which preferably includes a ridge waveguide structure.