Taken from the fiber core axis (center of core), the measurement is the square root of the squared refractive index of the core minus the squared refractive index of the cladding. See critical ...

The numerical aperture of a spherical lens, abbreviated NA, can be calculated from the effective focal length and thediameter of the input source. For collimated incident light, when the refractive ...

A paper titled "Three-dimensional large-aperture lens antennas with gradient refractive index," published in SCIENCE CHINA Information Sciences, 2013, No. 12, investigates the principles and ...