Green lasers have attracted tremendous attention due to their potential in full-color mobile projectors, optical data storage, and medical and military applications. Especially, the market volume of the mobile projectors is estimated to be over 10 million in the next 5 years. The most advanced technique for generating green laser is the “direct emission laser diode” known to be implementable in quantum wells. While theoretical analysis suggests that quantum dot lasers with suitable heterostructures perform better than the quantum well lasers in various aspects, no experimental result has yet been reported.
Quantum Dot Green Laser
A research group in the Electrical Engineering and Computer Science of University of Michigan has reported the competitive characteristics of self-organized InGaN/GaN quantum dot lasers, where the laser heterostructures are grown on c-plane GaN substrates. Particularly, emission above threshold is characterized by a peak at 524 nm (green) and linewidth of 0.7 nm. The lowest measured threshold current density is 1.2 kA/cm2 at 278 K. The slope and wall plug efficiencies are 0.74 W/A and ~1.1%, respectively, at 1.3 kA/cm2. The value of T0=233 K in the temperature range of 260–300 K. The group also provides one method for developing the desired laser heterostructures, which is verified by atomic force microscopy and scanning electron microscopy.
Applications and Advantages
- Projection display
- Optical data storage
- Low power consumption
- Simple structure for generating green lasers