The disturbance imposed to the stream will grow on the surface of the stream as the stream flows downward. The growth of the disturbance continues until a fluid parcel is pinched off. The fastest growth rate is related to the controllable parameters such as the speed of the jet and the frequency of the disturbance. This paper presents an experimental and analytical study to examine the breakup of a round jet into a droplet stream. The range of the speed of the jet and the frequency of the disturbance in the uniform droplet singlet oxygen generator were acquired.