Phase-matched third-harmonic generation of Nd: Glass-laser picosecond pulses in a new cyanine-dye solution

The phase-matched direct tripling of picosecond light pulses of a mode-locked Nd: glass laser in a new cyanine dye PMC is studied. The solvents trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP) are applied. The S0–S1 absorption peak of the dye is around ?=480 nm and the absorption cross section at the third-harmonic wavelength of ?3=351.3 nm is only s3˜1×10-19 cm2. Phase-matching occurred at concentrations of CPM=0.0874 mol/dm3 in HFIP and 0.1088 mol/dm3 in TFE. A third-harmonic energy conversion efficiency of ?E˜0.01 was achieved at a pump-laser peak intensity of I0L˜2.5×1011 W/cm2 in a 5 mm long sample of PMC in TFE. The conversion efficiency is limited by destruction of phase-matching due to the intensity-dependent nonlinear refractive index of the dye solutions.