Speckle-Free Phosphor-Scattered Blue Light Emitted out of InGaN/GaN Laser Diode with Broadened Spectral Behavior for High Luminance White Lamp Applications

Ultra-high luminance lamps emitting white light with a well-scattered blue spectrum from InGaN/GaN laser diodes and a phosphor-converted yellow spectrum show speckle contrast values as low as LED. Spectral behavior of the laser diodes is analyzed to find the reason why such low values are obtained. As a result, the PWM-driven, multilongitudinal mode with dynamically broadened line-width is found to have a great effect on reducing speckle contrast. Despite using the lasers, such speckle-free lamps are considered to be very suitable for high-luminance and other various lighting applications. key words: laser diode, phosphor, lighting, speckle, spectral broadening