# Difference between amplitude modulation and intensity modulation

If a few kHz modulation is imposed on the 80MHz pulse train of a laser by the means of either a Mch-Zehnder interferometer or a single acousto optical modulator triggered by an external function generator, what kind of modulation is taking place? Amplitude modulation or intensity modulation?

• modulation in amplitude leads to modulation in intensity, so is there some important difference that you are thinking about (nonlinearity)? – AmIAStudent May 16 at 3:32
• "If a few kHz modulation" this is frequency modulation and it does not affect (much) the amplitude or the intensity ( which is a function of average amplitude) pbs.org/wgbh/aso/tryit/radio/radiorelayer.html em waves have the same mathematical description for all frequencies. – anna v May 16 at 3:41
• @AmIAStudent Actually your answer better rephrases my question. "modulation of amplitude leads to modulation in intensity". So the question is still under normal circumstances is amplitude modulation same to intensity modulation or is there a fine difference between these two? – user188062 May 16 at 4:03
• @annav actually this few kHz is significant. So much so that I am using this as a reference for my lock in amplifier to extract signals. – user188062 May 16 at 4:05
• amplitude of electromagnetic waves is conventionally described by the E field, a time varying vector. en.wikipedia.org/wiki/Electromagnetic_radiation#Properties . intensity is given by the average of the amplitude as the Poynting vector hyperphysics.phy-astr.gsu.edu/hbase/Waves/emwv.html – anna v May 16 at 4:15