(color online) The evolution of bubble structure when the chirped laser pulse propagates through the under-dense plasma (n _e = 0.02n _c). The evolution of the bubble in the case of the negatively chirped pulse with the chirped parameter of b = –0.08 at the times of: (a1) t = 300 fs, (a2) t = 500 fs, and (a3) t = 600 fs. The evolution of the bubble in the case of the positively chirped pulse with the chirped parameter of b = 0.08 at the times of: (b1) t = 300 fs, (b2) t = 500 fs, and (b3) t = 600 fs. The other laser parameters are the same as the un-chirped case.