Time- and Frequency-Domain Characteristics of Direct-Detection Acousto-Optic Delay Lines

We discuss various details regarding the practical use of direct-detection acousto-optic delay lines, and develop a mathematical model for the input signal. An expression for the transient response was obtained and used to determine the acousto-optic delay line response to an boxcar input signal. This expression for the transient response was used to determine the cutoff frequency of the acousto-optic delay line and derive an equation for the impulse response to determine the acousto-optic transmission coefficient of the acoustooptic delay line as a function of frequency. The resulting equations are confirmed by numerical examples. The numerical results were in turn experimentally validated using the direct-detection acousto-optic delay line model developed in this paper. The theoretical and experimental results were compared using two criteria: the output response to a boxcar input signal and the cutoff frequency of the frequency response curve. The cutoff frequency was obtained using an oscillogram of the output pulse and the experimentally determined frequency response. A comparison of the theoretical and experimental results indicated that the time- and frequency-domain equations for the response curves have high potential for time-domain processing of broadband analog signals.