We have evaluated the suitability of two commercial external-cavity, tunable diode lasers (tuning range approximately 770–800 nm) for use as Raman excitation sources. The tests consisted of relatively long-term (up to 14 h) measurements of wavelength and power stability as well as measurements of reproducibility of emission wavelength during repeated on/off cycling. We find that, for both tested lasers, the external cavity configuration either eliminates or dampens “mode-hopping” and wavelength drift to a level suitable for obtaining good-quality Raman spectra in most routine experiments. Over the course of several hours, wavelength change from both mode-hopping and drift is less than approximately 0.05 nm for the New-Focus laser and 0.07 nm for the SDL laser. Reproducibility over several on/off cycles is of the same order of magnitude. In all cases, resolution measurements were limited by the spectrographs.
External cavity diode lasers with 5kHz linewidth and 200nm tuning range at 155μm and methods for linewidth measurement