Semiconductor laser module having an improved temperature control

Abstract

A semiconductor laser device is provided including semiconductor laser element, a PN-junction element which is used for temperature detection, and a thermoelectric heat pump which is electrically connected to the PN-junction element. According to this arrangement, heat developing from the semiconductor laser element is sensed by exploiting the fact that the forward voltage V.sub.F of the PN-junction element or PN-junction diode changes in correspondence with the change of the ambient temperature (this phenomenon itself is a matter already known), and the change of the forward voltage V.sub.F is fed back to the thermoelectric heat pump. Therefore, even when the semiconductor laser device is placed in the condition of a very high ambient temperature (open air temperature), the semiconductor laser element is cooled down to a predetermined temperature by the thermoelectric heat pump so as to produce a prescribed optical power at all times. Thus, the semiconductor laser element itself is driven in an appropriate temperature condition (for example, 25.degree. C.), so that the degradation of the semiconductor laser element can be prevented.