Abstract

One can use stimulated Raman scattering to obtain a near-diffraction-limited Stokes beam from a multimode pump beam if the Raman amplifier is seeded with a TEM₀₀ Stokes beam. In this way a smooth beam is obtained from a rough beam; hence the term beam cleanup. We investigate the Raman amplifier configuration numerically, using various pump beam profiles. Analysis of the quality of the amplified beams is based on the M² concept. For Gaussian–Hermite pump beams, excellent beam cleanup with an M² near 1.0 is possible at low amplification. However, the M² increases rapidly for higher amplifications. For Gaussian–Schell-model beams, beam cleanup is limited even at low amplification to a reduction in the M² of approximately a factor of 2. Increasing the power of the initial Stokes TEM₀₀ beam reduces the M² of the Stokes beam at the output.

© 1995 Optical Society of America

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