Vertical-cavity surface emitting lasers: moving from research to manufacturing

After more than a decade of research, vertical-cavity surface emitting lasers (VCSELs) are making the transition into the manufacturing arena. We review unique VCSEL properties found in their structure, growth, fabrication, and performance, which have precipitated their commercial acceptance. The short optical cavity that is formed between two distributed Bragg reflector mirrors is a distinctive VCSEL attribute. The spectral alignment between the resonance of the optical cavity formed by these mirrors and the laser gain bandwidth is shown to influence the VCSEL performance. Thus, epitaxial VCSEL growth by metalorganic vapor-phase epitaxy aided by in situ reflectance monitoring is discussed with an emphasis on uniformity and reproducibility. We also describe the fabrication techniques and VCSEL structures used to obtain transverse electrical and optical confinement, including etched air-post, ion-implanted, and selectively oxidized VCSELs. For the latter, wet oxidation of AlGaAs to form buried-oxide apertures has enabled record laser performance, such as ultralow threshold current and high efficiency. Numerous applications for VCSELs have been identified that leverage their manufacturing and performance advantages.