PHASE-MATCHED 3RD-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 solve nts trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP) are applie d. The S0-S1 absorption peak of the dye is around lambda = 480 nm and the absorption cross section at the third-harmonic wavelength of lambd a3 = 351.3 nm is only sigma3 almost-equal-to 1 X 10(-19) cm2. Phase-ma tching occurred at concentrations of C(PM) = 0,0874 mol/dm3 in HFIP an d 0.1088 mol/dm3 in TFE. A third-harmonic energy conversion efficienCY of eta(E) almost-equal-to 0.01 was achieved at a pump-laser peak inte nsity of I(0L) almost-equal-to 2.5 x 10(11) W/cm2 in a 5 mm long sampl e of PMC in TFE. The conversion efficiency is limited by destruction o f phase-matching due to the intensity-dependent nonlinear refractive i ndex of the dye solutions.