ELIMINATION OF MODE HOPPING AND FREQUENCY HYSTERESIS IN DIODE-LASER RAMAN-SPECTROSCOPY - THE ADVANTAGES OF A DISTRIBUTED-BRAGG-REFLECTOR DIODE-LASER FOR RAMAN EXCITATION

A comparison is made between an index-guided (Fabry-Perot type) diode laser and a distributed Bragg reflector (DBR) diode laser as excitation sources for fiber-optic Raman spectroscopy utilizing charge-coupled device (CCD) detection and an image-corrected spectrograph. The DBR diode laser was superior to the index-guided diode laser for elimination of mode hopping, elimination of frequency hysteresis as a function of both temperature and current changes, and reduction in laser broadband emission. These advantages may allow the DBR laser to be used in industrial process control applications which are too demanding for index-guided diode lasers.