Homoepitaxial nonpolar (10-10) ZnO/ZnMgO monolithic microcavities: Towards reduced photonic disorder

Abstract

Nonpolar ZnO/ZnMgO-based optical microcavities have been grown on (10-10) m-plane ZnO substrates by plasma-assisted molecular beam epitaxy. Reflectivity measurements indicate an exponential increase of the cavity quality factor with the number of layers in the distributed Bragg reflectors. Most importantly, microreflectivity spectra recorded with a spot size in the order of 2 μm show a negligible photonic disorder (well below 1 meV), leading to local quality factors equivalent to those obtained by macroreflectivity. The anisotropic character of the nonpolar heterostructures manifests itself both in the surface features, elongated parallel to the in-plane c direction, and in the optical spectra, with two cavity modes being observed at different energies for orthogonal polarizations.

Voigt Exceptional Points in an Anisotropic ZnO-Based Planar Microcavity: Square-Root Topology, Polarization Vortices, and Circularity

“…The optical thickness of the cavity layer corresponds to 9/8 of the central wavelength of the DBR (≈ 400 nm), as previous numerical computations indicated this detuning well suitable for the observation of well-separated Voigt points [15,35]. All ZnO and Mg 0.29 Zn 0.71 O layers are m-plane oriented and reveal interface roughnesses below 1 nm [34]. The top-DBR was prepared non-epitaxially by pulsed laser deposition and consists of 6 pairs Al 2 O 3 and YSZ (Y-stabilized ZrO 2 ), all layers being optically isotropic [36].…”

“…We have fabricated an anisotropic ZnO-based planar microcavity: First, a 16× ZnO/Mg 0.29 Zn 0.71 O distributed Bragg reflector (DBR) and the ZnO cavity layer have been grown on m-plane oriented ZnO substrate by molecular-beam epitaxy [34]. The optical thickness of the cavity layer corresponds to 9/8 of the central wavelength of the DBR (≈ 400 nm), as previous numerical computations indicated this detuning well suitable for the observation of well-separated Voigt points [15,35].…”

Exceptional points in anisotropic planar microcavities

“…Hence, the conditions for EPs are satisfied: optical biaxiality and non-Hermiticity. The experimental feasibility of such structures has already been demonstrated [39][40][41]. Specifically, we propose a ZnO-based microcavity with dielectric Bragg reflectors (DBRs) consisting of layered pairs of Al 2 O 3 and Y-stabilized ZrO 2 .…”

Edge-emitting polariton laser and amplifier based on a ZnO waveguide

“…The sample W2 is a half-microcavity without any grating. The sample geometries together with fabrication details are presented in the supplementary material [49] and in [50]. The common aspect of both samples is the presence of regular horizontal cracks, as one can see in the SEM image (Fig.…”