Table of Contents
Principle of operation: LED vs semiconductor lasers
The operation principle of an LED and a traditional semiconductor laser system is practically the same, which means that light is emitted during the combination of electrons and holes. The main difference is that the light of LEDs is emitted in a narrow spectral range, while the light from semiconductor lasers is emitted in a single wavelength.
Emission wavelength and applications
The emission wavelength of devices depends on the materials used. Thus, semiconductor laser systems emit the wavelengths whose ranges vary from infrared to ultraviolet. The laser applications include such fields as fiber optic communication, barcode readers, disc readers, and laser printing, but the use of laser systems as an illumination product remained impractical up to now.
Resonant cavity in semiconductor lasers
Similar to conventional laser systems, semiconductor lasers have a resonant cavity to facilitate amplification; the cavity consists of two parallel planes, separated by a few hundred µm, that operate as mirrors to direct emitted photons back into the resonant cavity.
Comparison with LEDs
There are some similarities between traditional LEDs and semiconductor laser systems, for example, their source of power is a driver converting AC to DC; they both suffer from a drop in light output at increasing temperatures. Semiconductor lasers are not receptive to a “droop” process, during which the increase in drive current causes lower efficacy.
Advantages of laser-based headlamps
In spite of the fact that usual blue LEDs offer higher efficacy than semiconductor laser systems provide, this is so only at lower input currents. This is the reason why BMW company offers headlamps based on a laser system that makes them 10 times brighter than traditional LED headlamps and 30 percent more efficient.
Working principle of laser headlamps
The principle of the laser headlamps’ operation is based on the creation of white laser beams by reflecting semiconductor laser light around inside the headlamp body frame using accurately established mirrors, then focusing the laser beam through a phosphor-filled lens, producing a white light of high intensity.
Efficiency and future potential
Semiconductor laser systems can provide efficiencies of a hundred times or even more than that of traditional LEDs, allowing higher light output from the laser beam with smaller die sizes. The laser system still requires some improvements for future laser applications because of the extremely narrow emission cone (about 1-2 degrees).
Semiconductor laser systems will be applied in architectural illumination products for which a narrow, high-quality laser beam is advantageous. It is possible to place lighting for museums, galleries, retail spaces, and other settings in a small area instead of being spread throughout.