Enhanced spectrum superluminescent diodes fabricated by infrared laser rapid thermal annealing

We report on the fabrication of superluminescent diodes (SLD) from a graded bandgap quantum well intermixed (QWI) material obtained by an infrared laser rapid thermal annealing (IR Laser-RTA) technique. The processed semiconductor wafer consisted of an InGaAs/InGaAsP/InP (001) QW laser heterostructure originally emitting at 1.55 μm. The combined beams of a 150 W laser diode operating at 980 nm and a 30 W Nd:YAG laser operating at 1064 nm are used to heat the sample. While the laser diode is used for back-side heating of the wafer, the Nd:YAG laser beam is swept along the sample surface, resulting in temperature gradient changing in the direction perpendicular to the scan. This contactless RTA approach, allowed to obtain a graded bandgap material that was employed for the fabrication of SLD devices with a broadened emission bandwidth. The lasing effect in a series of 3 mm long broad area injection diodes was suppressed by tilting their facets by 7.5° with respect to the [110] direction. The best SLD devices had their FWHM (full-width-at-half-maximum) emission increased by 33% in comparison to the FWHM of 36 nm observed for devices made from the as grown material at an equal output power of 0.8 mW.