Nanoimprinted hyperlens array: Paving the way for practical super-resolution imaging
The concept of a perfect lens that can produce immaculate and flawless images has been the Holy Grail of lens makers for centuries. In 1873, a German physicist and optical scientist by the name of Ernst Abbe discovered the diffraction limit of the microscope. In other words, he discovered that conventional lenses are fundamentally incapable of capturing all the details of any given image. Since then, there have been numerous advances in the field to produce images that appear to have higher resolution than allowed by diffraction-limited optics.
In 2000, Professor Sir John B. Pendry of Imperial College London—the John Pendry who enticed millions of Harry Potter fans around the world with the possibility of a real Invisibility Cloak—suggested a method of creating a lens with a theoretically perfect focus. The resolution of any optical imaging system has a maximum limit due to diffraction but Pendry's theoretic perfect lens would be crafted from metamaterials (materials engineered to have properties not found in nature) to go beyond the diffraction limit of conventional lenses. Overcoming this resolution limit of conventional optics could propel optical imaging science and technology into realms once only dreamt by common Muggles.
Scientists all over the world have since endeavored to achieve super-resolution imaging that capture the finest of details contained in evanescent waves that would otherwise be lost with conventional lenses. Hyperlenses are super-resolution devices that transform scattered evanescent waves into propagating waves to project the image into the far-field. Recent experiments that focus on a single hyperlens made from an anisotropic metamaterial with a hyperbolic dispersion have demonstrated far-field sub-diffraction imaging in real time. However, such devices are limited by an extremely small observation area which consequently require precise positioning of the subject. A hyperlens array has been considered to be a solution, but fabrication of such an array would be extremely difficult and prohibitively expensive with existing nanofabrication technologies.
Read more.
