Tapered laser module at 636 nm with > 500 mW for display applications
Red-emitting diode lasers are needed as compact light sources not only for displays, but also for medical treatment and sensing applications. An important property required for these applications is high radiance (i.e. brightness). In the framework of the InnoProfile initiative „Hybride Diodenlasersysteme“, the FBH succeeded in developing a compact laser module with more than 500 mW output power at 636 nm wavelength. The module emits a nearly diffraction-limited, collimated beam with a radiance of more than 19 MW/cm²/sr. Perceived by a human eye, this corresponds to a luminance of more than 27 TCd/m² , which is more than 10,000 times brighter than the luminance of the sun (1.6 GCd/m²) – and a new record value for red-emitting diode lasers.
This result was made possible by the development of red-emitting tapered lasers and their subsequent mounting on CVD-diamond heat spreaders with two contacts. This allows optimal heat extraction from the chip and individual currents through the ridge-waveguide and taper sections of the laser. Additionally, the radiation of the chip was formed by micro-lenses mounted inside the module. The shaped beam could be coupled into an optical fiber featuring a small aperture of only 16 µm with an efficiency of more than 75%. Using this fiber, the laser light can then be guided to its point of use, e.g. a projector head of a laser display system.
 G. Blume, C. Kaspari, D. Feise, A. Sahm, B. Sumpf, B. Eppich, and K. Paschke, “Tapered diode laser modules at 638 nm with efficient fiber coupling “, IEEE Phot. Technol. Lett. (submitted 05.01.2012).