We studied both numerically and experimentally the transverse modes near degenerate resonator configurations such as g<sub>1</sub>g<sub>2</sub>=1/4, 1/2, 3/4 in a simple plano–concave Nd:YVO<sub>4</sub> laser with a small pump size. We found that there are stationary modes that show an additional beam waist besides the well-known waist on the flat mirror end near g<sub>1</sub>g<sub>2</sub>=1/4, 3/4. When the specific modes of the three degeneracies propagate through a lens, they are capable of exhibiting multiple beam waists. The multibeam-waist mode possesses a small waist size without a ring structure in the near field on the flat mirror end; nevertheless, it has a far-field pattern with many concentric rings. The numerical results show good agreement with the experimental observations. Furthermore, by simultaneously considering the wavelike and the raylike character of the multibeam-waist mode, we found that it can be represented as a superposition of <i>N</i> consecutive round-trip electric fields of period-<i>N</i> solution in the degenerate empty cavity, where N=2 for g<sub>1</sub>g<sub>2</sub>=1/2 and N=3 for g<sub>1</sub>g<sub>2</sub>= 1/4, 3/4.
© 2003 Optical Society of America
(140.0140) Lasers and laser optics : Lasers and laser optics
(140.3480) Lasers and laser optics : Lasers, diode-pumped
(140.3580) Lasers and laser optics : Lasers, solid-state
(140.4780) Lasers and laser optics : Optical resonators
Ching-Hsu Chen, Po-Tse Tai, Wen-Feng Hsieh, and Ming-Dar Wei, "Multibeam-waist modes in an end-pumped Nd:YVO4 laser," J. Opt. Soc. Am. B 20, 1220-1226 (2003)