TRANSVERSE BEAM PROFILE CHARACTERISTICS OF TRAVELING-WAVE PARAMETRIC GENERATION IN KTIOPO4 CRYSTALS

Transverse beam profile characteristics of traveling-wave parametric g eneration in KTiOPO4 crystals are investigated. Transverse beam profil e depression and splitting due to the back-conversion in the parametri c propagation process were observed even when the conversion efficienc y was less than 10%. We measured the walk-off angle dependence and pum p energy dependence of the transverse beam profiles. The transverse be am profile is ring shaped when there is no walk-off and deforms by exp anding to the walk-off direction when walk-off exists. By decreasing t he pump intensity, the deformation of the profile can be reduced due t o the subsequent reduction in back-conversion. Walk-off compensation w ith two crystals placed next to each other with one in the opposite di rection is also useful for getting a better transverse beam profile.