Based on the original design of T.G.Leighton's conical bubble U_tube，an improve d apparatus is set up. The light pulses and spectra of air bubbles in water are detected. Results show that the width of a light pulse ranges from a few of hun dred picoseconds to a few nanoseconds. The vibrational spectra of water molecule s in the near_infrared have been obtained，and its intensity increases toward th e infrared. The spectra of conical bubble in NaCl solution is also detected.