Long wavelength VCSELs made by wafer fusion

Long wavelength (LW) vertical cavity surface emitting lasers (VCSELs) are important low cost and low power consumption sources for optical interconnects in data centers, sensing and spectroscopy [1,2]. We discuss here the recent progress in the design, fabrication and industrialization of such devices made by using wafer fusion, which allows integration of GaAs-based distributed Bragg reflectors (DBRs) with InP-based active structures and an independent optimization of the mirror and active cavity properties before the fusion. Both the GaAs-based mirrors and InP-based optical gain structures are grown by metalorganic vapor phase epitaxy (MOVPE). The VCSEL structure comprises an InP-based active region with 5 to 6 InAlGaAs compressively strained quantum wells (QWs) as the gain medium and tunnel junction (TJ) aperture for current and optical confinement, double-fused to two GaAs/AlGaAs-based Bragg mirrors (Fig.1a). By epitaxial growth, device design and processing optimization 1.3- and 1.5μm waveband VCSELs emitting single mode power of 6–8-mW at room temperature and up to 3-mW at 80°C were demonstrated (Fig.1b) [3,4]. Moreover, industrially manufactured 10-Gb/s full CWDM wavelength-set VCSEL devices for coarse wavelength division multiplexing systems with high yield and Telcordia-reliability have been developed [5–6].