I am interested in the effect frequency modulation has on the signal.
I am using an acousto-optic deflector to steer a laser beam. The deflector receives a Radio-frequency (RF) signal (~100 MHz, sine-like) in order to deflect the beam. By changing the RF frequency, one can control the deflection angle.
E.g. by changing the frequency from 70 MHz to 130 MHz I can perform a linear sweep of the laser beam.
The frequency spectrum of output signal strongly depends on the frequency of the frequency modulation.
If the sweep is done slowly (low frequency of frequency modulation), the frequency spectrum look clean (equal contribution of all frequencies).
The corresponding image on a CCD camera would look something like this:
If the sweep is done quickly (high frequency of frequency modulation), the spectrum gets some oscillating form and some frequencies are less prominent.
The corresponding image on a CCD camera would look something like this:
I understand that this behavior is solely comes from the Fourier transformation of the frequency modulated signal. However, my question is, how to obtain the shape (in time) of the sweep of the laser beam?
