While the epi-side of the laser is fully covered by a 4μm-thick gold contact, the window contact is initially a square window with a width of 100μm and a thickness of 4μm, but here an additional grid-like gold contact only 268nm thick is deposited on top of the former to optimize the current injection. The 1.5x1.5mm device was demonstrated to operate at room temperature at a wavelength of 8.75μm and a maximum peak power up to 5W.
The authors aim to further improve power output thanks to a more powerful electrical driver and by improving the regrowth planarization process, but also by experimenting with other PhC pillar shapes less sensitive to fabrication imperfections. The device didn’t have any anti-reflection coating on the substrate surface. The paper concludes that although the PhC-QCL process used is far from being mature, the laser already competes with other state of the art devices in the mid-infrared region.
ETH Zurich - ethz.ch/en.html