Macroscopic broadband optical escalator with force-loaded transformation optics.

Transformation optics enables one to guide and control light at will using metamaterials. However the designed device is deterministic and not flexible for different objects. Based on force-loaded transformation optics we propose a force-induced transformational device, which can realize dynamic escalator metamorphosing continuously between optical elevator and invisibility cloak. This escalator can visually lift up and down the perceived height of a plane fixed in space by controlling the forces loaded in different directions. Or conversely, the escalator can physically lift up and down a plane while visually maintaining the same height to an outside observer. One can quickly adjust this device to the required demand without changing the background index, while the usual transformation cloak will be detectable due to the lateral shift from mismatched background. The schematic is self-adaptive, multi-functional, and free of metamaterial or nanofabrication. Our work opens a new perspective in controlling light dynamically and continuously, empowering unprecedented applications in military cloak, optic communication, holographic imaging, and phase-involved microtechnique.