Holographic Storage of Electric Signals

In the holographic storage of electric signals, a pulsed electric input signal is converted to a one dimensional spatial transmittance function by an ultrasonic light modulator. This transmittance function, which travels in the light modulator at a speed characteristic of the acoustic medium, may be viewed as a one-dimensional scene undergoing constant-speed linear motion. It is possible to record the Fourier transform hologram of the pulsed signal by compensating the reference beam in a straightforward manner. Reference beam compensation permits the use of a longer exposure time than would otherwise be allowed in the formation of the hologram of a moving scene. Reconstruction of the original electric signal is effected by forming the Fourier transform of the holographic recording in a coherent optical spectrum analyzer. Electric signals with 19-microsec duration, 1-MHz bandwidth, and 20-MHz carrier frequency were successfully recorded and reconstructed by this technique.