A THEORETICAL EXAMINATION OF OFF-AXIAL DIRECTIONALITY IN LIGHT FROM OPTICAL MASERS.
MINNESOTA UNIV MINNEAPOLIS DEPT OF ELECTRICAL ENGINEERING
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This dissertation is concerned with the evaluation of the field distribution at the mirrors which gives rise to the rings in the far field and an explanation as to why such field configurations are preferentially present. It is established that the rings are due to the propagation of high order TE and TM modes in the cavity. This is done by calculating the far-field pattern when the distribution characteristic of such modes exists at the aperture of optical masers. The angle of the ring has been related to the order of the mode. The appearance of rings at certain discrete angles has been explained by proving that the frequency degeneracy in a multimode cavity is dependent on the angle the wave vectors in the plane wave representation of the modes make with the axis. A very general method is used to prove that non-uniformities in the gain distribution inside the cavity lead to mixing of modes with the creation of new modes with reduced thresholds of oscillation. This extends the work of Collins and Giordmaine Proc. of III International Congress in Quantum Electronics, Paris. Columbia Univ. Press, 1964 who came to the same conclusions for the case when there are nonuniformities in the reflectivity of mirrors.