  We present a high sensitivity single-monochromator Raman spectrometer which
allows operation with a tunable laser source. The instrument is based on the
modification of a commercial Raman spectrometer; such instruments operate with
holographic Rayleigh filters which also act as a laser mirrors and are usually
considered as inherently narrow-band. In our design, the two tasks are
separated and the filter can be freely rotated without much effect on the light
alignment. Since rotation shifts the filter passband, this modification allows
tunable operation with efficient stray light filtering down to 150 1/cm. The
design is optimized for single-wall carbon nanotubes, for which the performance
is demonstrated using a tunable dye-laser source. The spectrometer thus
combines the high sensitivity with the broadband characteristics of usual
triple monochromator systems.
