The compact laser used for visibility studies, i.e. absolute measurement of aerosol light absorption in the atmosphere, is shown above along with a pocket knife for scale. The laser beam output is mechanically chopped at the resonance frequency of the acoustic resonator. A small power supply (not shown) provides power for the laser as well as temperature control. For diesel vehicle exhaust applications, and/or for measurement of ambient black carbon content, a 1047 nm laser can be used. This laser is in the same package as the one shown above, though it can be directly modulated rather than requiring use of a chopper.