EXPERIMENTAL AND NUMERICAL STUDY OF STIMULATED RAMAN-SCATTERING IN ANASTIGMATIC FOCUS

An astigmatic focus has been used to increase the conversion efficienc y of a Raman cell at high pump energy. Experimental and numerical resu lts show that the increased conversion is due to the reduction of casc ade second order Stokes. It is shown that other effects, namely Brillo uin scattering, anti-Stokes generation, and ground-state depletion are negligible for our experimental setup. The experimental and numerical calculations correspond. In particular, the pump energy where the con version for an ordinary focus is identical to an astigmatic focus is r eproduced by the calculations. Below this energy an ordinary focus giv es a higher conversion than an astigmatic focus, while above this ener gy this is reversed.