The Bivoj team, led by Dr. Martin Divoky, and Dr. Jonathan Phillips from STFC have successfully demonstrated high energy third harmonic generation (THG) at 343 nm with a nonlinear LBO crystal at Bivoj laser system as a sum frequency of fundamental and second harmonic frequencies. Radiation at 515 nm was obtained from the SHG experiment performer earlier this year and the proper ratio was achieved by slight detuning of the SHG crystal. The THG experiment was performed utilizing the nanosecond Bivoj laser system at 1030 nm with the output energy of 5.5 J at 10 Hz. The aperture and the length of the second LBO crystal were 30 x 30 mm2 and 12 mm, respectively. Figure below shows the long-term THG output energy (blue line) and the total fundamental energy (thick red line). Over an extended period of 60 minutes, the conversion efficiency remained stable with a THG energy stability of 2% rms.
Future plans include an upgrade of laser beam distribution system for propagation of fundamental, SHG and THG beams to the target chambers. This will greatly enhance spectrum of experiments that can be performed by user on Bivoj laser system. We anticipate that the second and third harmonic beams will be available to users from 2020. Those experiments can involve processing of materials by high energy with this specific wavelength. A wide range of materials have a significantly greater absorption of 515 nm or 343 nm laser radiation and this allows us to efficiently process non-ferrous metals such as copper or aluminum alloys. Likewise, this wavelength is little absorbed by water, so we can conduct experiments under water for specific industrial applications. Very interesting application is also the possibility of testing optical components in this expanding field of green and blue lasers usage.