We report on the design and fabrication of heterogeneous and compact surface-emitting microlasers, optically pumped and operating at 1.5μm at room-temperature. A very low threshold, below 15μW, is achieved. The devices consists of a top two-dimensional InP photonic crystal slab, including four InAsP quantum wells, a SiO2 bonding layer, and a bottom high index contrast Si∕SiO2 Bragg mirror deposited on a Si wafer. The graphitelike photonic crystal lattice is tailored for vertical emission. We theoretically and experimentally demonstrate that the Bragg reflector can strongly enhance the quality factor of the photonic crystal resonant mode, leading to a drastic decrease of the lasing threshold.

It is emphasized that two-dimensional photonic crystals (2D PC) have not only a great potential for the development of 2D nanophotonics in the inplane waveguided configuration, but that they may also open the way to other brilliant developments, with an extension to out-of-plane operation, along a 2.5D nanophotonics approach. In this 2.5D approach, a 1D-2D high index contrast lateral structuration is combined with a 1D high index contrast vertical structuration, using multilayer membrane stacks including 1D-2D photonic crystal membranes, thus resulting in so-called 2.5D PC. As a specific illustration of recent achievements along this approach, new families of VCSEL structures are presented.Examples of 2.5D photonic structures. a) A monolithic version, where a vertical stack of III-V semiconductor micro-structured membranes are suspended by surface micromachining. b) A heterogeneous version, where vertical integration of active and passive micro-structured membranes is achieved by bonding technologies.

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