A compact high pulse energy Ti:Sapphire laser with its third harmonic has been developed for airborne ozone differential absorption lidar to study the distribution and concentration of ozone throughout the troposphere. The Ti:Sapphire laser, pumped by a commercial frequency-doubled Nd:YAG laser with a pulse repetition frequency of 20 Hz is seeded by a single mode 900 nm diode laser. More than 130 mJ/pulse was achieved at the fundamental wavelength of 900 nm. Two nonlinear, Lithium Triborate crystals were used for the Third Harmonic Generation resulting in output pulse energy of more than 39mJ at 300nm, which is used as the off-line wavelength of an airborne ozone DIAL system. The energy conversion efficiency from 900 nm to 300 nm was 30 percent as compared to the theoretical value of 36 percent.