Recent breakthroughs in growth of novel wide-bandgap materials, and in the design of high brightness light-emitting diodes (LEDs) have resulted in the
development of a new exciting solid-state lighting technology . In addition to future application for general lighting, mass applications of solid-state lighting now include full-color video displays, signals, traffic lights, and local and decorative illumination. In addition, many niche applications in phototherapy, photosynthesis, and optical measurements have emerged. In 2020, solid-state lighting is expected to save up to 10% of the global electric power consumption and replace a significant percentage of ineffective incandescent bulbs and mercury-containing discharge tubes.
In our talk, we review the history of lighting, LED basics, extraction of light from semiconductor chips, white and UV LEDs, and new applications of solid-state lighting. We also describe our work on optimization of solid-state lighting sources and on the development of versatile white polychromatic lamps with digital feedback that are being tested for a more effective treatment of seasonal affective disorder. Novel application of high-power LEDs for Raman measurements and for water testing is also demonstrated.
 A. Zukauskas, M. S. Shur, and R. Gaska, Introduction to Solid-State Lighting (Wiley, New York, 2002).