Spontaneous mode locking In long-cavity Fabry-Perot xenon lasers

Abstract

Spontaneous mode locking or self-locking has been shown to be critically dependent on aperture size, excitation current, and the position of the active medium inside the cavity. However, in most previous experimental and theoretical work, a cavity length of not more than a few meters has been used. Our experiments have focused on a 3.51-μm Xe laser with a cavity length of up to 36 m. The characteristics of self-locking have been examined as functions of excitation current, cavity length, and aperture diameter. Unlike the shorter cavity lasers, the long laser remains self-locked for a wide range of excitation current and for various cavity configurations. It is found that the number of pulses per round-trip time increases with increasing cavity length. Furthermore, for a sufficiently long cavity and close to threshold, other pulses appear as ringing of the fundamental 2L/cpulse, where L is the cavity length and c is the speed of light. This behavior is consistent with numerical results based on a semiclassical model for an inhomogeneously broadened laser.