Characteristics of a Rubidium Metal Vapor Filter for Laser Scatter Rejection in Single Molecule Detection

The characteristics of a rubidium metal vapor filter (MVF) for its use as a laser scatter filter for single molecule detection (SMD) were investigated. This investigation was done by a simulation along with experimental observation. A monochromator was used to elucidate the spectral components of the background in SMD. The major contributors to the background were laser transmission and fluorescence of the rubidium vapor. Experiments on the filter's performance under varying conditions such as MVF temperature, MVF pressure, and laser power were done. It was found that the integrated transmission intensity decreased with increasing pressure and temperature while it increased for increasing laser powers. The computer simulation modeled the experimentally observed profiles very well. Through the simulation, it was determined that the limitation on the attenuation by the MVF was due to the transmission of the broad-band stimulated emission "wings" of the Ti:sapphire laser.