Scientists at Rensselaer Polytechnic Institute’s Lighting Research Center (LRC) will spend the next three years developing cutting edge lighting technologies that will someday replace lighting systems that have been used for the past 100 years.
The LRC is collaborating with the University of California at Santa Barbara (UCSB) to create a solid-state lighting system that will achieve high-quality white light with reduced energy consumption compared to the most efficient lighting systems currently available. The U.S. Department of Energy’s Energy Efficiency Science Initiative is underwriting this nearly $3 million project.
UCSB researchers, led by Dr. Shuji Nakamura, developer of the world’s first GaN (Gallium Nitride) LED, will work on the semiconducting element. Scientists at the LRC, led by Dr. N. Narendran, director of research, will work on integrating these semiconductors with optics and electronic controls. These will lead to novel lighting fixtures for general lighting applications. Solid-state lighting, which includes LEDs, is a rapidly evolving technology that holds significant promise for energy savings and long life, and it is environmentally friendly.
“The 20th century” explains Dr. N. Narendran, “had just two basic lighting technologies: incandescent and fluorescent. Every lighting innovation to date has sprung from those basic methods of illumination.” Now, he says, that’s about to change.
"The demand for lighting is increasing every year," says Dr. Narendran. "As we know, California couldn't meet energy demand last year. Energy-efficient solid-state lighting systems could be one way to prevent this from happening again."
UCSB will create GaN-based vertical cavity surface-emitting lasers, or VCSEL’s. These are commonly known as laser diodes and will produce radiation in the blue to UV region. The devices will then excite phosphors to produce white light. The VCSEL design is an important feature, according to Dr. Narendran. While LED devices tend to trap most of the light they produce, VCSEL’s can improve light extraction and become very efficient solid-state lighting devices.
“The challenge for the LRC is to take these laser-like devices created by UCSB and develop a light fixture suitable for illumination purposes,” says Dr. Narendran. These fixtures, he adds, must produce high quality white light in order to be acceptable for general lighting. A diverse team of scientists at the LRC will tackle that challenge.
The Lighting Research Center uses a multidisciplinary approach, and the project will utilize the skills of various LRC lighting scientists, from specialists in optical design, photometry, and electronics, to vision science and human psychology. This team will develop target specifications for the color properties of the new light source before conducting optical modeling using the semiconducting laser source developed by UCSB. The LRC will then use this information to develop unique lighting fixtures.
Dr. Narendran explains that another challenge confronting the LRC is packaging the semiconducting devices. The clear materials typically used to encapsulate LEDs tend to yellow over time. “We are working with leading polymer chemists at Rensselaer to develop suitable, non-yellowing polymers that can be used to encapsulate these new semiconductors.”
This cutting edge research could lead to revolutionary changes in the way we light our surroundings, including user-controlled, integrated lighting systems comprised of illuminated walls, ceilings, and even shelving that could change light color and intensity on demand. Integrating these new systems into intelligent, computer-controlled buildings may also make emergency lighting systems more effective by responding instantly to rapidly changing situations.
During the first year of the project, UCSB will create the GaN-based light sources. The LRC will identify specifications and develop optical models for the lighting fixtures. UCSB will improve the efficiency of the semiconducting devices, over the second year, to a point where they are twice as efficient as currently available light sources. The LRC, meanwhile, will produce laboratory prototype fixtures using the UCSB devices. By the end of the third year, the LRC hopes to equip a room with this new lighting system to run comparison evaluations with traditional lighting systems.
When the three-year project concludes, Dr. Narendran says he hopes that the two groups will have shown the feasibility of energy-efficient, solid-state illumination systems.