DeepLightSeekDefinition:
Phase delay per unit length, or this value divided by 2π.
Phase delay per unit length, or this value divided by 2π.
There are different definitions for wavenumber. The physical definition is:
where λ is the wavelength in the medium (not the vacuum wavelength). The wavenumber is the magnitude of the wave vector and represents the phase delay per unit length during the propagation of a plane wave.
Another definition is:
Its unit is cm⁻¹, which is commonly used in spectroscopy. To avoid confusion, the first quantity can be referred to as the angular wavenumber (analogous to angular frequency), although this terminology is not very common.
The wavenumber of a light wave in a medium is equal to the vacuum wavenumber multiplied by the refractive index.
The wavenumber is related to the phase change per unit length when a plane wave propagates in an isotropic medium. For a focused beam, the phase change per unit length requires some corrections based on the plane wave model. For example, the correction term for a Gaussian beam is the Gouy phase shift. For guided waves propagating in a waveguide, the imaginary part of the propagation constant γ (also denoted as β) is related to the phase change per unit length.
