Journal Title

American Journal of Physics

Publication Date



We describe an experiment for generating and characterizing a beam of collimated blue light (CBL) in a rubidium vapor.Two low-power, grating-feedback diode lasers, operating at 780.2 nm (5S3/2 → 5D5/2) and 776.0 nm (5P3/2 → 5D5/2), respectively, provide step-wise excitation to the 5D excited state in rubidium. Under the right experimental conditions, cascade decay through the 6P excited state will yield a collimated blue (420-nm) beam of light with high temporal and spatial coherence. We investigate the production of a blue beam under a variety of experimental conditions and characterize the spatial coherence and spectral characteristics. This experiment provides advanced undergraduate students with a unique opportunity to investigate nonlinear optical phenomena in the laboratory and uses equipment that is commonly available in laboratories equipped to investigate diode-laser-based absorption spectroscopy in rubidium.


Coherent states; Nonlinear optics; Nonlinear optics--Materials--Congresses; Rubidium; Undergraduates

Publication Information

American Journal of Physics, 2013, Volume 81, Issue 6, 442-449.

© 2013 American Association of Physics Teachers

Archived version is the final published version.





Document Type

Journal Article

Included in

Optics Commons