Two of the most successful microcresonator concepts are the vertical cavity surface emitting laser (VCSEL), where light is confined between distributed Bragg reflectors (DBRs), and the distributed feedback (DFB) laser, where a periodic grating provides positive optical feedback to selected modes in an active waveguide (WG) layer. Our work concerns the combination of both into a composite device, facilitating coherent interaction between both regimes and giving rise to novel laser modes in the system. In a first realization, a full VCSEL stack with an organic active layer is evaporated on top of a diffraction grating with a large period (approximately 1 micron), leading to diffraction of waveguided modes into the surface emission of the device. Here, the coherent interaction between VCSEL and WG modes, as observed in an anticrossing of the dispersion lines, facilitates novel hybrid lasing modes with macroscopic in-plane coherence [1]. In further studies, we decrease the grating period of such devices to realise DFB conditions in a second-order Bragg grating which strongly couples photons via first-order light diffraction to the VCSEL. This efficient coupling can be compared to more classical cascade-coupled cavities and is successfully described by a coupled oscillator model [2]. When both resonators are non-degenerate, they are able to function as independent structures without substantial diffraction losses. The realization of such novel devices provides a promising platform for photonic circuits based on organic microlasers. [1] A. Mischok et al., Adv. Opt. Mater., early online, DOI: 10.1002/adom.201600282, (2016) [2] T. Wagner et al., Appl. Phys. Lett., accepted, in production, (2016)

Hybrid resonators in vertical and lateral direction are introduced by depositing a full vertical cavity surface emitting laser (VCSEL) stack on top of a periodically structured substrate. As a result, waveguided (WG) modes in the cavity plane are scattered into the vertical direction and exhibit linear dispersion curves in addition to the original parabolic cavity mode. A large in-plane coherence length even below threshold enables a coherent interaction of both resonators, as observed in a pronounced anticrossing and hybridization of waveguided and VCSEL modes in the far field spectrum. Resulting from this coupling, both original VCSEL modes as well as hybrid WG-VCSEL modes show stimulated emission. Here, hybrid modes exhibit a macroscopically increased spatial extension of the coherent laser mode, proven by both spatially resolved spectra as well as sharp modes in k-space. The coherent coupling of two conceptually very different devices with perpendicular propagation directions facilitates a multitude of new applications.

A. Mischok and co-workers develop a hybrid waveguide–vertical cavity surface emitting laser on page 1215. An angle-resolved emission spectrum of such a hybrid laser is presented on their cover image. The linear dispersion lines of an organic waveguide are scattered into the surface emission of a microcavity via a high-order diffraction grating and enable the observation of novel hybrid laser modes (red) with a macroscopically increased coherence length.

Two of the most successful microresonator concepts are the vertical cavity surface emitting laser (VCSEL), comprising a vertical cavity of highly reflective DBRs sandwiching an active layer, and the distributed feedback (DFB) laser, where a periodic optical grating selects laser modes from an active waveguide (WG) layer. Here, an organic microcavity is coupled with in-plane periodic photonic wires or dots to facilitate a coherent interaction between waveguided and vertically emitting modes as well as creating an additional in-plane confinement. The vertical positioning of such patterning plays a crucial role in the observable features. While embedding metallic or dielectric wires directly in the cavity layer leads to a strong lateral confinement as well as the observation of photonic Bloch states [1,2], the deposition of the full VCSEL stack on top of a periodic grating reveals novel features. In such a device, we demonstrate the coherent coupling between parabolic VCSEL and linear WG modes in the angle-resolved far field emission. In this system, lasing occurs not only at the VCSEL parabola apex but also at points of hybridization, when the dispersion of modes cross, showing a drastically enhanced in-plane coherence [3]. The coherent coupling of two conceptually different devices with perpendicular propagation directions paired with the macroscopic coherence facilitate a multitude of new applications. [1] Adv. Opt. Mater. 2(8), 746 (2014) [2] Phys. Rev. Appl. 3, 064016 (2015). [3] Adv. Opt. Mater. under review (2016).