High-speed and High-Brightness Zn-Diffusion VCSELs at 850 and 940 nm Wavelengths

High brightness and high-speed VCSEL array plays important role in the fields of sensing and communications. The high brightness beam with narrow divergence angle can minimize the diffraction loss in the receiver-ends. There are three major ways to increase the brightness of beam output from VCSEL array. First is to reduce the mirror reflectivity for a higher output power, however, this approach results in the increase of RIN and seriously degrades the quality of eye-patterns under large signal modulation. The second is to narrow down the divergence angle of far-field patterns (FFPs) of VCSEL outputs. However, the reported solutions for FF patterns narrowing usually lead to spatial hole burning effect and un-desired low-frequency roll-off in the E-O response. The third issue is to reduce the size of light-emission active area, which can be realized by minimizing the spacing between neighboring unit VCSEL in the array. In this work, we demonstrated a novel VCSEL array structure, which can have a compact device active area, FFPs with narrow divergence angles, and high-quality eye patterns under large signal modulation. Here, the pitch size between different light-emission apertures is as small as 20 μm, Compared with the traditional VCSEL array, the unique point of our one is that we have dual pads for DC and DC+RF current injections, respectively. This dual pad one can have a higher output power (105 vs. 94 mW) than that of reference with a single pad under the same total bias current (180 mA). The measured far-field 1-D and 2-D patterns of the dual pad one exhibit Gaussian FFPs with the divergence angle as narrow as 7° (FWHM). Such array can attain a16 GHz 3-dB bandwidth and error-free 32 Gbit/sec transmissions (under ~200 mA bias current). Overall, the demonstrated device structure opens new possibilities for VCSEL array with higher brightness output with better eye-openings at higher modulation speed.