SIMULTANEOUS PHASE-LOCKING OF LONGITUDINAL AND TRANSVERSE LASER MODES

By using a discharge tube filled with pure neon as a nonlinear element, it has been found possible to obtain simultaneous locking of both longitudinal and transverse modes of a 6328 Å He–Ne laser. Under certain circumstances, each transverse mode has all its longitudinal resonances phase locked to form a narrow pulse, but the pulses corresponding to the various transverse mode orders do not coincide in time. Beam scanning has been observed when the frequency spacing between the transverse modes is a simple fraction of the longitudinal mode spacing. Under these conditions, a ``spot'' of light traces out a zig-zag path in the laser cavity.