Multiple-wavelength GaInAs/GaAs VCSELs with grading a spacer layer for short reach WDM applications

We propose and demonstrate a simple method to fabricate the multiple-channel vertical cavity surface emitting laser (VCSEL) arrays emitting at 980 nm by grading the first low-index spacer layer of SiO₂/Ta₂O₅ di-electric mirror using wet etching technique. A multi-step exposure to UV lithography followed by selective wet chemical etching has been done to create spacer layer gradients. A 4-channel 980 nm VCSELs with wavelength span exceeding 30.0 nm are demonstrated. We also show the scalability of 8-channel VCSEL array using the same technique. All VCSELs show good single mode laser performances having the average output power nearly 0.5 mW with the side mode suppression ratios between 30-45 dB.