where h and c are Planck's constant and vacuum speed of light, respectively.
The third term accounts for the simulated photons; σ se is the stimulated emission cross section of DCM, and c is the vacuum speed of light.
Compared to normal structures, our new designed nonlinear photonic crystal coupled cavity waveguide owns group velocity that is three magnitudes smaller than the vacuum speed of light.
In our study, the central wavelength is assumed to be λ0 = 1.5 μm and the frequency can be obtained as ω0 = 2πc/λ0, where c is the vacuum speed of light.
The transition from the echo ranges measured in the so-called virtual space (where the difference between the group speed of the high-frequency (HF) electromagnetic waves in plasma and the vacuum speed of light is neglected) to actual spatial coordinates is essential for accuracy of our analysis.
According to the theory of optical tweezers [ 7]: F L = n P / c, (2 where n denotes the index of incident media, P is the power of source, and c the vacuum speed of light.
For Doppler imaging, conversion from measured Doppler shift (fd) to velocity (v) used the standard Doppler equation for echo-based Doppler velocimetry (fd=2vcos n ν/ c; θ, Doppler angle; n, tissue optical index; ν, optical frequency; c, free-space vacuum speed of light).
where n is the refractive index of the solution and λ is the wavelength in vacuum of the incident light.
When Maxwell discovered that the equations that united electricity with magnetism called for the propagation of electromagnetic waves in a vacuum at the speed of light, it was suggested that the vacuum was not empty but filled with an elastic medium -- the aether -- whose excitation produced the phenomenon of light.
where k 0=ω/c is the vacuum wave number, c the speed of light in vacuum, and ε 1 and ε 2 are the permittivities of the media at frequency ω.
