Abstract
A terahertz vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated using an active focusing reflectarray metasurface based on quantum-cascade gain material. The focusing effect enables a hemispherical cavity with flat optics, which exhibits higher geometric stability than a plano-plano cavity and a directive and circular near-diffraction limited Gaussian beam with M2 beam parameter as low as 1.3 and brightness of 1.86 × 106 Wsr-1m-2. This work initiates the potential of leveraging inhomogeneous metasurface and reflectarray designs to achieve high-power and high-brightness terahertz quantum-cascade VECSELs.
Highlights
The ability to engineer the phase of scattered light from planar surfaces is a powerful tool for beam engineering, which allows one to replace bulky optical components with thin and flat equivalents
A terahertz vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated using an active focusing reflectarray metasurface based on quantum-cascade gain material
The focusing effect enables a hemispherical cavity with flat optics, which exhibits higher geometric stability than a plano-plano cavity and a directive and circular neardiffraction limited Gaussian beam with M2 beam parameter as low as 1.3 and brightness of 1.86 × 106 Wsr−1m−2
Summary
The ability to engineer the phase of scattered light from planar surfaces is a powerful tool for beam engineering, which allows one to replace bulky optical components with thin and flat equivalents This concept was introduced in the microwave regime in the form of the reflectarray antenna, often used to replace space-fed parabolic reflectors [1,2,3]. There has been relatively little experimental work on integrating gain into the metasurface itself, whether for mitigating losses, or for implementing new laser concepts [10,11,12,13,14] This is understandable, since in the infrared and visible the metallic/plasmonic elements that make up many metasurfaces are prohibitively lossy [15]. The situation is quite favorable in the terahertz frequency range, where metals have sufficiently modest losses that quantum-cascade (QC) lasers can effectively use sub-wavelength metallic waveguides [16]
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