SEMICONDUCTOR-LASERS FOR SPECTROSCOPY

We consider semiconductor diode lasers as tunable light sources for spectroscopic purposes. Generally, only about one third of the wavelengths of the potential tuning curve of a solitary semiconductor diode laser can be realized. We describe a simple set-up in which the laser, by means of weak optical feedback, is forced to oscillate at a wavelength that cannot be reached by the solitary laser. Furthermore, we discuss the spectral consequences of the aging process of semiconductor diode lasers: during the first hundred hours of operation the emitted wavelength shifts. We also describe the spectral behaviour of semiconductor diode lasers, of which the injection current is modulated: the modulation frequency ranges from the MHz to the GHz regime.