Polarization fluctuation dynamics was studied in the X-cut and XY-cut KDP crystals under square pulses employing the Barkhausen type experimental technique.
Resonance type fluctuations were observed; the resonance amplitude was proportional to the input square pulse amplitude but independent of the pulse width.
Approaching the phase transition temperature, the amplitudes and the resonance frequencies were observed to display the characteristic phase transition anomalies near $T_c$.
It seems that the transversal dielectric fluctuations become strongly coupled with the longitudinal fluctuations as the transition temperature is approached.
