A fluorescence detection process begins by localizing rubidium 87 atoms within an optical (all-optical or magneto-optical) trap so that at least most of the atoms in the trap are within a cone defined by an effective angle, e.g., 8°, of a spectral filter. Within the effective angle of incidence, the filter effectively rejects (reflects or absorbs) 778 nanometer (nm) fluorescence and effectively transmits 775.8 nm fluorescence. Any 775.8 nm fluorescence arrive outside the effective angle of incidence. Thus, using an optical trap to localize the atoms within the cone enhances the signal-to-noise ratio of the fluorescence transmitted through the spectral filter and arriving a photomultiplier or other photodetector, resulting fluorescence detection signal with an enhanced S/N.