- #1
Albe5588
- 2
- 0
Hello everybody,
I'm new. It's a long time a have a big (probably stupid) doubt about the interaction between light and media, and now it's time to solve it. The doubt its essentially concerning the difference between an antenna and a photodetector: the first one is able to detect the amplitude and the phase of an electromagnetic wave, the second one detects the power.
To what I know, the principle of functioning of an antenna is completely different from a detector, because its based on the generation of "surface" alternate current by the electric field impinging a metal, while a detector is based on the photoelectric effect.An optical wavelength cannot be detected in its amplitude and phase like a GHz one, because electrons in media are too slow to follow the electric field variation at hundread of THz.Now, we can calculate the conductivity as a function of the frequency of an external electromagnetic excitation, starting from the Kubo formula.
The question is: is the Kubo formula an equation to calculate the conductivity in the sense of an antenna or in the sens of a photodetector? what I mean is: if I calculate the conductivity at a certain frequency, is this conductivity linked with a varying current at the same frequency of the field, or it is linked to a dc current generated by the photoelectric effect?
I don't know if I was clear, and I admit that I have a lot of confusion about this argument, that's why I need your help :)
I'm new. It's a long time a have a big (probably stupid) doubt about the interaction between light and media, and now it's time to solve it. The doubt its essentially concerning the difference between an antenna and a photodetector: the first one is able to detect the amplitude and the phase of an electromagnetic wave, the second one detects the power.
To what I know, the principle of functioning of an antenna is completely different from a detector, because its based on the generation of "surface" alternate current by the electric field impinging a metal, while a detector is based on the photoelectric effect.An optical wavelength cannot be detected in its amplitude and phase like a GHz one, because electrons in media are too slow to follow the electric field variation at hundread of THz.Now, we can calculate the conductivity as a function of the frequency of an external electromagnetic excitation, starting from the Kubo formula.
The question is: is the Kubo formula an equation to calculate the conductivity in the sense of an antenna or in the sens of a photodetector? what I mean is: if I calculate the conductivity at a certain frequency, is this conductivity linked with a varying current at the same frequency of the field, or it is linked to a dc current generated by the photoelectric effect?
I don't know if I was clear, and I admit that I have a lot of confusion about this argument, that's why I need your help :)