We pushed direct green laser diodes towards longer wavelengths at 524–532 nm based on improvements of epitaxial design and material quality on c-plane GaN substrate. Mounted ridge laser diodes show significant performance improvement in cw operation. For 524 nm laser, wall plug efficiency up to 2.3% at 50 mW optical output power is achieved. In pulse mode operation we demonstrate broad-area test lasers with an emission wavelength of 531.7 nm. Nonpolar and polar substrates are compared with respect to indium content in InGaN quantum wells. The limiting factors for achieving longer wavelengths and better performance of green lasers are discussed from this viewpoint.

We demonstrate direct green laser operation from InGaN based diodes at wavelengths as long as 515.9 nm with 50 mW output power in pulse operation. A factor of ∼10 defect reduction for the In-rich InGaN quantum wells based on improvements of the epitaxial growth process and design of the active layers on c-plane GaN-substrates makes it possible to demonstrate laser operation at room temperature. Micrometer-scale photoluminescence mappings and electro-optical measurements confirm the reduction of nonradiative defects in the emitting layers. The 11 μm broad-area gain-guided laser structures were driven in pulse operation to minimize thermal effects and to accurately measure the laser temperature dependence. The threshold current density was ∼9 kA/cm2 and the fitted slope efficiency had a value of ∼130 mW/A for an optical output up to 50 mW.

In this paper we investigate the waveguiding (WG) of direct green InGaN laser diodes grown on c-planeGaNsubstrates. The problem of parasitic modes emerges due to the reduced refractive index difference between the GaN waveguide and AlGaN cladding layers for green compared to blue emitting laser diodes. We discuss several approaches to avoid substrate modes. We investigate different materials and designs for optimized WG of green InGaN laser diodes using a 1D transfer matrix simulation tool

Experimental gain spectra of 450 and 490 nm laser diodes on c-plane GaN are analyzed by detailed comparison with the results of a fully microscopic theory. The gain calculation shows the importance of electron LO-phonon coupling. The whole spectral gain shape, not only the low energy tail, is strongly influenced by the LO-phonon contribution. The inhomogeneous broadening parameter increases by a factor of about two for the cyan laser diode in comparison with the blue laser structure. This indicates an increase in alloy and thickness fluctuations for the longer wavelength material