SoraaLaser, the laser-focused outgrowth of blue/white-LED Nobel laureate Shuji Nakamura’s Soraa LED lighting company, have developed the first commercially viable, efficient solid-state, white-light laser source. It boasts a luminance up to 100 times better than that of white LEDs.
Using semipolar GaN laser diodes and phosphors, SoraaLaser have produced white-light SMDs (surface-mount devices) that produce up to 500 Lm from a 300-μm emitting area, enabling collimated beam angles as narrow as 1 to 2° with compact optics.
To produce these white-light laser SMDs, a high-power blue InGaN semipolar laser diode excites a very small (ø< 300 μm) remote phosphor target that converts the laser light to eye-safe, broad-spectrum, incoherent white light. Highly directional light with less than 2° of divergence from a ø25mm optic is possible.
The 7×7-mm SMD package consists of the blue laser diode chip illuminating a 300 μm area of the 1×1-mm phosphor in a reflective configuration, with a “beam dump” that blocks any blue light that could reflect from the single-crystal phosphor. To harness the 1000 cd/mm2 luminance from the Lambertian emission of a single 7-mm2 SMD, ø25 to 50-mm collimating optics are used, producing a luminaire with a tenth of the beam angle of an LED-based luminaire of the same size and lumen output. In other configurations, this technology enables luminaires with 1/10 the diameter of LEDs, with 100 × the lumen output of a typical LED.
Even though the efficacy (in Lm/W)) of laser diodes, at 30–40%, is less than the 50–60% efficacy of LEDs, the key metric in directional lighting applications is Lm(target area)/W. By this metric, laser-diode illumination improves dramatically beyond 10 m compared to LEDs. As efficacy continues to improve for laser diodes, this gap is expected to carry on shrinking.
