A cartridge and cartridge system for use in an apparatus for analyzing a sample are provided. The system has a plurality of cartridges for different applications for a multimode instrument. The cartridges are removably engaged with a cartridge support in a “plug-in” format such that one cartridge may be removed from the apparatus and another cartridge may be easily installed. The cartridge support includes a plurality of cartridge positions that receive cartridges concurrently. One of the cartridges is a wavelength-tunable cartridge in which different light sources, excitation filters, and/or emission filters may be selected. Tuning is further accomplished by tilting the excitation or emission filters at desired angles relative to a beam of exciting light or emitted light.