Ultra-Compact Vertical-Cavity Surface-Emitting Lasers Using a Double Set of Photonic Crystal Mirrors

It is well known that high-contrast metastructures can be exploited to perform a controllable coupling between matter and electromagnetic radiation. At optical frequencies this paves the way toward an arbitrarily adjustable spatio-temporal molding of light at the wavelength scale. In detail, high-index-contrast periodic structures such as photonic crystal membranes (PCMs) can be used for controlling the resonant coupling of radiated light to "heavy photons" states in strongly corrugated waveguides, thus putting photons through a slowed-down transport regime which results in an efficient quasi-3D light harnessing. More recently, one-dimensional Si/SiO2 photonic crystals have been adopted as compact, flexible, and power-efficient mirrors in vertical-cavity surface-emitting lasers (VCSELs) emitting in the C-band which have been realized within a mass-scale fabrication paradigm by employing standard 200-mm microelectronics pilot lines. The extreme flexibility of such innovative photonic architecture enables to perform a fully-controllable transverse mode filtering, including polarization and far-field control, while the strong near-field mode overlap within mirrors can be exploited to implement unique optical functions such as on-chip optical routing and enhanced sensing capabilities. Furthermore, the device compactness ensures a considerable reduction in footprint, power consumption and parasitics, adding in required features for broadband modulation and high-speed data processing. High fabrication yields obtained via molecular wafer bonding of III-V alloys on silicon conjugate excellent device performances with cost-effective high-throughput production, addressing industrial needs for a fast research-to-market transfer. In conclusion, photonic crystal VCSELs constitute thus a robust high-performance building block for the follow-through of semiconductor lasers, VCSEL and silicon photonics.