High luminous flux from single crystal phosphor-converted laser-based white lighting system

Area of Science:

• Solid State Lighting
• Optoelectronics
• Materials Science

Background:

• Light emitting diodes (LEDs) suffer from efficiency droop at high current densities, necessitating multiple dies for high-power applications.
• Laser diodes (LDs) offer constant carrier density and high efficiency at elevated current densities, making them suitable for power-intensive illumination.

Purpose of the Study:

• To investigate the potential of a blue Gallium Nitride (GaN)-based laser diode coupled with a cerium-doped yttrium aluminum garnet (YAG:Ce) crystal for white light illumination.
• To evaluate the performance of a single phosphor-converted laser diode (pc-LD) die for high-power applications.

Main Methods:

• Utilized a continuous wave (CW) high-power blue GaN-based LD integrated with a single crystal YAG:Ce sample.
• Measured luminous efficacy, luminous flux, voltage, and current under various operating conditions.
• Performed simulations to assess thermal quenching effects in the YAG:Ce sample.

Main Results:

• A single pc-LD die achieved a peak luminous efficacy of 86.7 lm/W at 1.4 A and 4.24 V.
• A peak luminous flux of 1100 lm was recorded at 3.0 A and 4.85 V, with a luminous efficacy of 75.6 lm/W.
• Simulations indicated no thermal quenching in the YAG:Ce sample at peak LD operating efficiency.

Conclusions:

• A single pc-LD die demonstrates sufficient luminous flux for high-power white light illumination systems.
• This approach effectively bypasses the efficiency droop issue inherent in conventional LEDs.
• The findings suggest a promising alternative for efficient and high-output solid-state lighting solutions.