High-power bright white light using laser sources
October 30th, 2013
An alternative to light emitting diodes
White light emitting diodes (LEDs) are an efficient, long-lasting, and environmentally benign option to light our homes and workplaces. This technology commonly uses a blue-emitting LED coupled with a phosphor material that converts some of the blue light to other colors in the visible spectrum, ranging from green to red. The combination of colors produced by the device fills a large portion of the visible spectrum, creating white light. White LEDs have proven to be a viable lighting option to replace incandescent and fluorescent light sources for everyday use, but what about high-brightness applications such as car headlights, street lamps, parking lots, auditoriums, and sports stadiums?
A potential solution for LEDs in high-brightness applications
Unfortunately, as the operating power of LEDs increases, the efficiency decreases. This effect, known as droop, limits the overall light output of the device. Researchers at UC Santa Barbara have recently addressed the issue of droop at high operating power by turning to an alternate method of light generation, namely laser diodes.
In a recent study (referenced below), we demonstrated that high-power, bright white light can be produced using a laser diode in combination with phosphor materials. The laser diode is operated at a power much higher than possible with LEDs, without efficiency loss. This breakthrough allows a higher light output and enhanced brightness. The color quality of the white light produced using a laser is equivalent to the light quality produced with an LED. A variety of color temperatures — ranging from “cool” white to “warm” white with a high color rendering index — are realized, simulating sunlight.
A phosphor sample without (left) and with (right) excitation with a blue laser, producing bright white light.
Next steps for research
Currently, laser diodes are not as efficient as LEDs, but with increasing research in the area of laser diodes and phosphor materials, further improvements can be envisioned. This technology opens new avenues for generation of high-power white light for high-brightness applications, potentially enabling the replacement of traditional light sources with more energy efficient lighting systems.
Author: Kristin Denault, October 2013
Department of Materials, UC Santa Barbara
Authors and publication details:
K. A. Denault, M. Cantore, S. Nakamura, S. P. Denbaars, and R. Seshadri, "Efficient and stable laser-driven white lighting." AIP Advances 3 072107 (2013).