This is a photo montage of the Rb D1 fluorescence at 795 nm, when natural Rb vapor is irradiated with emission from a Photodigm 780 nm DBR laser tuned to be resonant with the D2 transition. The DBR laser has a linewidth of less than 1 MHz, much larger than the natural linewidth of the D2 resonance transition. Because the Rb light emission is at the very edge of the perception of human vision, we darkened the room and let our eyes accommodate. We current tuned the 780 nm DBR laser until we observed the faint resonance fluorescence at 795 nm. The fluorescence was photographed using a Nikon D70 DSLR with a Wratten 87 filter, which effectively blocked out all light below about 750 nm. We used a several second exposure to capture the image. Our electrical engineer Judy was separately photographed observing the emission, and the two images were overlayed in Adobe Photoshop. Photo by Martin Achtenhagen. Copyright Photodigm.
