Instability in a laser-diode-pumped microchip Nd YAG laser in a Pi scheme
Intrinsic instability and locking of pulsation frequencies in free-running two-mode class-B lasers It is known that single-mode class-B lasers, in whichpolarization dynamics is adiabatically eliminated, exhibit no ...
Intrinsic instability and locking of pulsation frequencies in free-running two-mode class-B lasers
It is known that single-mode class-B lasers, in whichpolarization dynamics is adiabatically eliminated, exhibit no dynamical instabilities without introducing additional degrees of freedom in the form of modu-lations, saturable absorbers, intracavity second-harmonic generation, light injections, external feedback, and so on. Recently, several self-induced instabilities that result from the inherent nonlin-earities of multimode class-B lasers were demon-strated.1 - 6 In microchip LiNdP4 O12 lasers, atomicinterference arises as a result of inherent simulta-neous oscillations on different transitions that form a L scheme. This nonlinear effect becomes apparent because the photon lifetime is an order of magnitude shorter than the lifetime of lower-level populations in a short-cavity configuration. Low-frequency coherence results in intensity pulsations.1 - 3 As for Nd:YVO4solid-state lasers, because of the substantially large inhomogeneous broadening that results from un-usual crystal fields, intensity-dependent cross-gain coupling among longitudinal modes induces such dynamical instabilities as locking of pulsation fre-quencies, quasi-periodic and chaotic oscillations, and Q -switching-type spiking oscillations and associated instabilities.4 - 6 In this Letter we demonstrate, for the first time to our knowledge, self-induced pulsations in a laser-diode-pumped Nd:YAG laser in the so-called P scheme, in which lasing occurs that involves 1064.1-and 1064.5-nm transition oscillations. The key be-hind the observed instability is that lasing takes place that involves excited Nd atoms in Stark-split upper laser levels whose population distribution obeys Boltzmann’s law, whereas the Nd populations in the lower laser levels are negligibly small. These prop-erties induce coupling between two otherwise isolated two-level transitions.
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