John Pendry

John Pendry theoretically demonstrated that materials with electromagnetic properties not found in nature, such as negative-refractive-index materials (metamaterials) can be realized by designing microstructures smaller than the wavelength of the target electromagnetic waves, thereby laying the groundwork for creating innovative materials such as “superlenses” with subwavelength resolution and “invisibility cloaks.”

The artificial design of materials with tailored electromagnetic properties is difficult because such properties are typically determined by the crystal structure and electronic configuration of a material. However, John Pendry’s theoretical work showed that metamaterials (materials with unique electromagnetic properties that do not exist in nature and have not been experimentally explored) can be created by designing structures smaller than the wavelength of the electromagnetic waves of interest. Specifically, he showed that utilizing the resonant states of small structures with respect to electromagnetic waves enables negative permittivity in materials consisting of metallic wire arrays (1) and negative permeability consisting of nonmagnetic conductor split ring structures (2). Furthermore, he demonstrated that materials composed of both wire arrays and split ring structures simultaneously exhibit negative permittivity and negative permeability (3). Although in the 1960s, materials with both negative permittivity and permeability were predicted to have a negative refractive index, Pendry succeeded in constructing a theoretical framework to design such materials. Shortly thereafter, based on his theory, metamaterials exhibiting negative refractive indices were experimentally realized for the first time.

The fundamental concept underlying Pendry’s metamaterials, based on which novel electromagnetic properties arise from structures on scales smaller than the wavelength, expands the possibilities for adjusting the properties of the material. For instance, negative refractive materials exhibit unique properties such as refracted waves at interfaces propagating opposite to the incident waves. Leveraging these properties of negative refractive metamaterials, Pendry proposed the concept of a “superlens” (perfect lens) that can achieve ideal infinite resolution without limitations arising from diffraction boundaries (3). The development of various devices using these lenses, including subwavelength microscopes, is currently being vigorously pursued worldwide. Furthermore, Pendry introduced “transformation optics,” using coordinate transformations in Maxwell’s equations to control the paths of electric fields, magnetic fields, and energy flows (4). This concept has considerably enhanced the design flexibility of optical components and has been applied in the design of various metamaterial devices. Notably, his proposal of an “invisibility cloak” that utilizes the design flexibility of the electromagnetic properties in metamaterials to reroute light around a shielded area and force it to its original path, effectively rendering the area invisible, has attracted widespread attention from both the academic community and general public. In collaboration with an experimental research group, Pendry has successfully demonstrated this property with the use of artificially structured metamaterials at microwave frequencies (5).

Pendry’s research has led to considerable advancements in metamaterials research worldwide since the early 2000s. Metamaterials are expected to have various applications in microwave control, heat shielding, optical, and optical communication technologies. They are also applied to wave fields other than electromagnetic ones, such as acoustics. Thus, Pendry’s innovative theoretical research on metamaterials has considerably advanced the field of materials science, created new interdisciplinary research areas, and paved the way for the development of novel materials with widespread social applications. His achievements are highly esteemed.

References
(1) Pendry JB et al. (1996) Extremely Low Frequency Plasmons in Metallic Mesostructures. Phys. Rev. Lett. 76 (25): 4773–4776.
(2) Pendry JB et al. (1999) Magnetism from Conductors and Enhanced Nonlinear Phenomena. IEEE Trans. Microw. Theory Tech. 47 (11): 2075–2084.
(3) Pendry JB (2000) Negative Refraction Makes a Perfect Lens. Phys. Rev. Lett. 85 (18): 3966–3969.
(4) Pendry JB, Schurig D, & Smith DR (2006) Controlling Electromagnetic Fields. Science 312: 1780–1782.
(5) Schurig D et al. (2006) Metamaterial Electromagnetic Cloak at Microwave Frequencies. Science 314: 977–980.