Risk, with a large computer company, Timothy R. Gosnell (Los Alamos National Laboratory), and Arto V. Nurmikko (engineering and physics, Brown U.) describe three approaches for generating blue-green light: the nonlinear frequency conversion of infrared lasers, upconversion lasers, and wide-bandgap semiconductor diode lasers. They include some material on basic concepts of nonlinear optics, rare-earth spectroscopy, and semiconductor device physics for readers without that background.