Single-mode proton-implanted photonic crystal VCSELs

Photonic crystals are etched to a variety of depths in the top mirror of proton-implanted vertical-cavity surface-emitting laser (VCSEL) diodes to achieve single-fundamental-mode operation. To investigate both the index confinement provided by the etched pattern and its effect on optical loss, continuous-wave experiments are performed. It is shown that proper pattern design leads to improved fundamental-mode output power, decreased threshold, and increased efficiency relative to unetched, but otherwise identical implant VCSELs. These improvements indicate a significant reduction in diffraction loss to the fundamental mode due to the index guiding provided by the etched pattern. Etching to shallow depths provides the ability to scale to large aperture sizes while etching deeply allows single-mode emission of small diameter devices. The photonic crystal designs are then used in the fabrication of high-speed implant-confined VCSELs with coplanar contacts on polyimide. Optimized devices exhibit a record 15 GHz small-signal modulation bandwidth.