Our group uses two triple-grating monochromator Raman spectrometers. The Horiba Jobin-Yvon T64000 and the Dilor XY. When selecting the two systems the focus was set to spectral flexibility. The use of triple-monochromator setups has advantages and disadvantages. The disadvantage is that the transmission is worse when compared to e.g. notch filters but whereas notch filters are restricted to only one wavelength the triple-monochromator configuration ensures the separation of excitation light and Raman signal over a wide range of energy.
The T64000is equipped with a Coherent MBR-110. This laser can be tuned continuously from approx. 670-1070nm. Furthermore, there is a Coherent MBD-200 frequency doubler available. With the help of the frequency doubler the laser can be tuned from 335nm to 535nm.
The Dilor Raman spectrometer is equipped with an Innova Spectrum 70C Argon-Krypton laser. This laser offers multiple discrete laserlines between 450nm and 650nm. For measurements at low temperatures a cryostat is also available
By using tunable lasers, we can cover a large spectral range to easier detect resonances in electronic and optical excitations of nano materials such as carbon nanotubes, nanowires and graphene. These resonances enhance the Raman signals and make many phenomena observable in the first place. Furthermore, tunable laser systems allows to investigate the coupling between lattice vibrations and certain electronic excitations.