Intracavity Second-Harmonic Generation Ring Lasers

We shall describe the spectrum, temporal dependence, and efficiency of intracavity second harmonic generation ring lasers (ISHRL). We solve for the dynamics of ISHRL containing a homogeneously broadened gain medium, a phasematched doubling medium, a tuner, and a dichroic output coupler (see Fig. 1). The dynamics of each of these elements is described analytically (except for the doubling element, which must be solved numerically if the slowly varying envelope of the electric field is complex, i.e., if FM modulation is present). We show that cw single-mode operation of ISHRL is stable against the growth of additional modes due to amplitude-modulated (AM) fluctuations of the fundamental, however, frequency-modulated(FM) fluctuations are not damped. Cw operation tends to single longitudinalmode output provided no frequency modulation arises. Multimode frequency-modulated cw operation can be achieved. Methods for achieving anti-modelocked laser output are described. We consider the temporal dependence and efficiency of Q-switched ISHRL. Comparision with the Q-switched fundamentallaser (not containing second harmonic generation) demonstrates that ISHRL can be even more efficient than the fundamental laser. General principles for assuring controlled intracavity fundamental intensity buildup are presented. Injection of multimode pulses and modelocked pulses into Q-switched ISHRL are considered.