The deposition of Ga on quartz substrates by photodissociation of trimethylgallium has been investigated. Light from a frequency doubled Ar-ion laser beam (257.2 nm) was focused onto quartz substrates. The Ar-ion laser was operated under CW or mode-locking conditions. The deposition rate has been investigated as a function of averaged UV power densities in the range of 1.8-1750 W/cm2 and is shown to depend critically on the laser operating mode. For CW operation, the maximum growth rate within the focal zone is limited to 17 Å/s whereas under mode-locking conditions, no saturation is observed and the growth rate increases linearly with the laser power up to 70 Å/s at 1.75 kW/cm2