Abstract
This research discussed the fractal dimension in spontaneous optical pattern formations. We calculated the fractal dimension of the optical patterns generated by optical modulation instability (MI). By calculating the fractal dimension, we found that at low intensity threshold, MI patterns can be regard as fractals due to its self-similar structure. We also found that as the voltage applied to the nonlinear crystal increases, the fractal dimension decreases. The decreasing rate is equal among different laser beam intensity. Finally, we found that the fractal dimension of the MI pattern fluctuated over time.