The majority of fluorescence flow cytome-ters now in use derive illumination from one or more lasers. Air-cooled argon ion lasers operating at 488 nm are the most commonly used light sources, but helium-neon (He-Ne) lasers emitting at 633 nm and diode lasers emitting at 635 nm have come into more widespread use as red-excited antibody labels and other fluorescent probes have become available. Other lasers sources used in fluorescence flow cy-tometry include argon, krypton, and mixed-gas ion lasers operating at wavelengths from the ultraviolet to the infrared; helium-cadmium (He-Cd) lasers emitting in the ultraviolet region at 325 nm and/or in the blue-violet region at 441 nm; and diode-pumped, frequency-doubled yttrium aluminum garnet (YAG) lasers emitting green light at 532 nm. A typical laser emits a beam on the order of 1 mm in diameter; efficient use of the laser light requires that this beam be shaped and focused to a smaller size to illuminate the cell stream passing through the flow cytometer. This unit will discuss spot size requirements and the methods by which optimal spot size is achieved.
Was this article helpful?