External cavity laser having improved single mode operation

摘要

Stable single mode operation of an external cavity semiconductor laser is obtained by a laser control method that monitors at least one optical beam which is generated by reflection from a wavelength selective element (18) within the laser cavity. The method of the present invention provides stable single mode operation and significantly decreases the mode hop rate, because the signal obtained by reflection from a wavelength selective element within the laser cavity provides a clear indication of an impending mode hop. <IMAGE>