Science of cloaking devices Metamaterial cloaking

1 science of cloaking devices

1.1 properties of optics , light
1.2 interest in properties of optics , light
1.3 perfect cloak , theory
1.4 challenges presented first cloaking device

science of cloaking devices

the purpose of cloaking device hide something, defined region of space invisibly isolated passing electromagnetic fields (or sound waves), metamaterial cloaking.

cloaking objects, or making them appear invisible metamaterials, analogous magician s sleight of hand, or tricks mirrors. object or subject doesn t disappear; vanishing illusion. same goal, researchers employ metamaterials create directed blind spots deflecting parts of light spectrum (electromagnetic spectrum). light spectrum, transmission medium, determines human eye can see.

in other words, light refracted or reflected determining view, color, or illusion seen. visible extent of light seen in chromatic spectrum such rainbow. however, visible light part of broad spectrum, extends beyond sense of sight. example, there other parts of light spectrum in common use today. microwave spectrum employed radar, cell phones, , wireless internet. infrared spectrum used thermal imaging technologies, can detect warm body amidst cooler night time environment, , infrared illumination combined specialized digital cameras night vision. astronomers employ terahertz band submillimeter observations answer deep cosmological questions.

furthermore, electromagnetic energy light energy, small part of visible light. energy travels in waves. shorter wavelengths, such visible light , infrared, carry more energy per photon longer waves, such microwaves , radio waves. sciences, light spectrum known electromagnetic spectrum.

the properties of optics , light

prisms, mirrors, , lenses have long history of altering diffracted visible light surrounds all. however, control exhibited these ordinary materials limited. moreover, 1 material common among these 3 types of directors of light conventional glass. hence, these familiar technologies constrained fundamental, physical laws of optics. metamaterials in general, , cloaking technology in particular, appears these barriers disintegrate advancements in materials , technologies never before realized in natural physical sciences. these unique materials became notable because electromagnetic radiation can bent, reflected, or skewed in new ways. radiated light slowed or captured before transmission. in other words, new ways focus , project light , other radiation being developed. furthermore, expanded optical powers presented in science of cloaking objects appear technologically beneficial across wide spectrum of devices in use. means every device basic functions rely on interaction radiated electromagnetic spectrum technologically advance. these beginning steps whole new class of optics has been established.

interest in properties of optics , light

interest in properties of optics, , light, date 2000 years ptolemy (ad 85 – 165). in work entitled optics, writes properties of light, including reflection, refraction, , color. developed simplified equation refraction without trigonometric functions. 800 years later, in ad 984, ibn sahl discovered law of refraction mathematically equivalent snell s law. followed notable islamic scientist, ibn al-haytham (c.965–1039), considered 1 of few outstanding figures in optics in times. made significant advances in science of physics in general, , optics in particular. anticipated universal laws of light articulated seventeenth century scientists hundreds of years.

in seventeenth century both willebrord snellius , descartes credited discovering law of refraction. snellius noted ptolemy s equation refraction inexact. consequently, these laws have been passed along, unchanged 400 years, laws of gravity.

perfect cloak , theory

electromagnetic radiation , matter have symbiotic relationship. radiation not act on material, nor acted upon given material. radiation interacts matter. cloaking applications employ metamaterials alter how objects interact electromagnetic spectrum. guiding vision metamaterial cloak device directs flow of light smoothly around object, water flowing past rock in stream, without reflection, rendering object invisible. in reality, simple cloaking devices of present imperfect, , have limitations. 1 challenge present date has been inability of metamaterials, , cloaking devices, interact @ frequencies, or wavelengths, within visible light spectrum.

challenges presented first cloaking device

the principle of cloaking, cloaking device, first proved (demonstrated) @ frequencies in microwave radiation band on october 19, 2006. demonstration used small cloaking device. height less 1 half inch (< 13 mm) , diameter 5 inches (125 mm), , diverted microwaves around itself. object hidden view, small cylinder, placed in center of device. invisibility cloak deflected microwave beams flowed around cylinder inside minor distortion, making appear if nothing there @ all.

such device typically involves surrounding object cloaked shell affects passage of light near it. there reduced reflection of electromagnetic waves (microwaves), object. unlike homogeneous natural material material properties same everywhere, cloak s material properties vary point point, each point designed specific electromagnetic interactions (inhomogeneity), , different in different directions (anisotropy). accomplishes gradient in material properties. associated report published in journal science.

although successful demonstration, 3 notable limitations can shown. first, since effectiveness in microwave spectrum small object invisible @ microwave frequencies. means invisibility had not been achieved human eye, sees within visible spectrum. because wavelengths of visible spectrum tangibly shorter microwaves. however, considered first step toward cloaking device visible light, although more advanced nanotechnology-related techniques needed due light s short wavelengths. second, small objects can made appear surrounding air. in case of 2006 proof of cloaking demonstration, hidden view object, copper cylinder, have less 5 inches in diameter, , less 1 half inch tall. third, cloaking can occur on narrow frequency band, given demonstration. means broad band cloak, works across electromagnetic spectrum, radio frequencies microwave visible spectrum, , x-ray, not available @ time. due dispersive nature of present-day metamaterials. coordinate transformation (transformation optics) requires extraordinary material parameters approachable through use of resonant elements, inherently narrow band, , dispersive @ resonance.