VCSEL Technology
Wafer fusion
Beam Express proprietary wafer fusion technology consists of bonding together the separate components of the VCSEL cavity that are grown on their own substrates. This approach combines InP-based active region with GaAs based-DBRs to give the best VCSEL performance.
A modified wafer fusion technique called "Localized wafer fusion" has been developed at Beam Express. In this technique one or more wafer surfaces are structured using conventional lithography prior to the fusion step. This surface structuring permits precise adjustment of the laser's optical-cavity length, which in turn enables nanometer-scale precision when setting its emission wavelength. In addition localized fusion helps to regulate the fusion process across the rest of the wafer, yielding reproducible high-quality fused interfaces with high uniformity and excellent repeatability.
The wafer fusion also provides unique possibilities for cavity length engineering and air-gap structures formation making possible the fabrication of multiple wavelength arrays and tunable VCSELs.
Long wavelength VCSELs made by localized double wafer fusion exhibit 85°C single mode output powers that are significantly higher than those of VCSELs made with other approaches, for both the 1310 and the 1550 nm wavebands. Wafer fusion (bonding) is now a well-established process, widely used in industry in silicon technology, which provides very reliable and reproducible results.
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