GaN Diode Lasers
We develop InGaN quantum well diode lasers whose performance is tailored for specific applications as, for example, atom spectroscopy, medical engineering, and bioanalytics. Some of the typical device requirements are a precisely defined emission wavelength, a narrow-band and temperature-stable emission, a long-term operation with moderate emission power under continuous driving current and a high beam quality.
Currently, we focus on the development of diode lasers with an emission wavelength of 380 to 440 nm. Broad area lasers reach optical output powers beyond 2 W in short pulse operation. Ridge waveguide diode lasers with a typical ridge width of 2 µm and a resonator length of 600 µm show lasing above approx. 50 mA and a maximum output power of 100 mW under cw operation. In cooperation with industry partners, lasers with monolithically integrated gratings, lasers in external cavities and hybride systems including tapered amplifiers are developed in order to achieve a high brilliance and beam quality at high optical output powers.
In close collaboration with TU Berlin, FBH covers the whole process chain for fabricating GaN diode lasers. MOVPE is used to epitaxially grow InAlGaN heterostructures on GaN substrates. We use various methods of material analytics to optimize the crystal perfection. Chip technology is carried out on the process line of FBH’s cleanroom, including the dry-etching of narrow ridge waveguides, the thinning and dicing of wafer in laser bars and single chips as well as the deposition of dielectric layers on the mirror facets. The chips are mounted either p-up or p-up on submounts and heat sinks using hard solder. Optical power-current-voltage characteristics in pulsed and cw operation, spectra as well as far-field and near-field distributions are recorded at variable temperature.